CRYSTAL GROWING! Detailed instructions with pictures on how to grow dozens of different types of crystals
(Click on main site to browse 70 other topics ranging from exotic kaleidoscope designs to the strange world of lucid dreaming. If you have any questions or suggestions please email me.)
Warning: The following procedures may require the use of hot liquids, dangerous chemicals, and sharp instruments. These procedures should only be attempted under adult supervision.
IMPORTANT NOTICE FOR STUDENTS AND TEACHERS!!!
If
you've come here looking for a science experiment for school and
decide crystal growing isn't what you want, please take a look at
some of the other science related pages on my HOMEPAGE.
Two-thirds of the way down this page is a section titled
"Science" in which you'll find links to 13 different
topics, covering everything from the physics of Silly
Putty to what
causes Wintergreen
Lifesavers
to flash when they are bitten,
any one of which would make an interesting project. Additionally,
under the "Gardening" heading is a write-up on growing
plants under Artificial
Lighting
with a plant
growing
test comparing
five different types of fluorescent bulbs. There are also pages
devoted to Kaleidoscopes,
Astronomy and two articles about what causes Brain
Freezes
and Colds
in the "Medical" section. I hope you find what you want on
this crystal growing page but if you don't perhaps you will on one of
these other pages.
Now,
let's
start growing some crystals!
Fast,
simple crystal growing projects
A salt garden (Good
for classroom demonstrations.)
The simplest,
fastest crystals of all to grow (Good for
classroom demonstrations.)
Super-fast
crystals (At last that's what one site claimed. I rate this as a dud.)
How to grow a
borax snowflake (Good for classroom demonstrations.)
A super-fast
crystal growing technique that really works (Good
for classrooms.)
Soap crystals
(Dud number 2)
How to grow
stalactites and stalagmites (Good for classroom demonstrations.)
Salt crystals
Vinegar/salt
garden (another dud)
Bicarbonate of
soda crystals (a semi-dud)
Advanced
crystal growing projects
Rock candy
Alum crystals
Growing
crystals in gelatin
Ultra-fast
sheet crystals (Good for classroom demonstrations.)
Monoammonium
phosphate crystals
Growing
large, high quality single crystals
Tricks of the
trade: hints on how to grow the best crystals
Alum crystals
Sugar crystals
Monoammonium
phosphate crystals
Epsom salt crystal
Exotic
Crystal Growing
Sodium
Thiosulfate Crystals (Good for classroom demonstrations.)
Copper Sulfate
Pentahydrate Crystals
Nickel Sulfate Crystals
Ferrous
Sulfate Crystals
Rochelle Salt
(potassium sodium tartrate)
Potassium
Chromate Crystals
Potassium
Dichromate Crystals
Silver
Crystals from Silver Nitrate
Potassium
Ferrocyanide Crystals
My
Choices for the Best Crystals to Grow
Snowflakes
How to grow
your own snowflakes indoors any time of the year!
Testing
a commercially available crystal growing kit
Online sources for crystal growing kits and chemicals
Other websites that explain how to grow crystals
Solubilities of common crystal growing chemicals
Upcoming crystal growing projects
Fast, simple crystal growing projects
The following techniques make use of ingredients available in all grocery stores, are quick and easy to put together and produce fast results, at least fast as far as growing crystals is concerned. The trade off for this simplicity and quickness is that the crystals are small to microscopic and form in dense clusters.
Salt Crystal Garden
Growing a salt garden is the most common crystal growing experiment mentioned in books and on the Internet, even beating out growing sugar crystals. These crystals normally grow white with some faint brown areas. The picture above shows what happens if a couples of drops of food color are dripped onto the material the crystals grow on.
The following formula and technique resulted from combining several different formulas obtained from the links in the Other websites that explain how to grow crystals section at the bottom of this page.
Note: although only household chemicals are used, some are toxic so this project should only be done under adult supervision.
Step 1: mix together:
4 tablespoons salt (one recipe recommended un-iodized salt.)
4 tablespoons liquid bluing (Mrs. Stewart's is available in the laundry department of grocery stores. One recipe called for using three times this amount. If you can't find bluing at a store near you, it is available on-line: http://www.mrsstewart.com)
4 tablespoons water
4 tablespoon ammonia (Some recipes use half this amount. One recipe calls for not adding the ammonia until the third day and then doubling the amount.)
Pour the mixture over small pieces of porous rock, charcoal or pieces of broken clay flowerpots in a shallow glass or plastic bowl or plate. (Some recipes suggest soaking the charcoal, etc. in water for 15 minutes then placing it in the bowl with the growing solution.) Crystals will begin to grow in six hours and continue for three days, depending on the humidity, temperature, and how much airflow is present. To concentrate crystal growth on the charcoal and avoid them forming on the edge of the plate, coat the plate with Vaseline.
Briquettes aren't very good at drawing the liquid up so be sure to keep the level of the liquid at least half way up the side of the briquette.
Most recipes suggest sprinkling two more tablespoons of salt over the charcoal and on the first or second day to get the crystal growth off to a faster start.
Add more of the salt-bluing-ammonia-water mix starting on the third day to keep the crystals growing. Be careful to avoid dripping any of the new solution on the growing crystals or they will be damaged. In time the crystals may grow over the sides of the bowl.
I've grown these crystals in both plastic and Corelle bowls and the growing liquid did not stain them. The crystals and any left over growing liquid washed off them very easily.
How it works:
The porous material draws the solution up using capillary action. Water evaporates on the surface and the solid chemicals are left behind forming crystals. Because the evaporation is a fast process compared to the rate of crystallization and there are many rough spots for nucleation (places where crystal growth begins) the crystals grown are small and may look like small grains or even powder.
Because evaporation drives this project, place it where it has free air circulation, but no hard drafts or the delicate crystals may be blow over. Warm dry areas will have faster growth than cool moist areas. Avoid direct sunlight because this causes the liquid to evaporate faster than the growing structure can draw it up so the crystals form on the plate instead of where they are supposed to. A gentle breeze from a small fan set on its lowest setting can increase the speed at which the crystals grow by a factor of ten.
Both crystals in the picture above started at the same time with the same amount of liquid. The one on the left was grown in quite air while the one on the right had a small fan very gently blowing on it. This represents 12 hours of growth. Without a fan the sample on the left would require three to four days to become as dense as the one on the right.
Bluing contains an iron compound that the ammonia breaks down into iron salts, which are added to the salt crystals as they form creating yellow and reds. At least this is what one site I visited said. All I noticed was a faint brownish coloring in some areas of the growth.
Another value of the bluing is that the material that gives it its blue color is an extremely fine powder. When this powder is mixed in with the salt solution it provided millions of microscope particles that act as nucleation sites for crystal growth.
As the first picture in this article showed, brighter colors can be added by dripping food color onto the charcoal. This is cheating, a little, because the crystals are being colored or painted instead of actually growing that color. Here's the picture again so it can be contrasted with a natural color above:
These crystals are very small and held together by the binding action of water, like fine mud. They are extremely fragile and a slight bump can cause them to collapse. Touch them and they smush (technical term for digital compression of soft, hydrated structures) to shapeless mush.
Experiments:
As simple as this technique appears, it none the less suggests many experiments suitable for classrooms. Here are several I tried and the results I got:
Does rubbing Vaseline on the sides of the growing bowl really prevent crystals from forming there?
No, but it does stop them from climbing up the sides of the bowl as they commonly do. The following picture shows crystals working their way up the side of the bowl:
What happens it that a spot on the edge of the liquid creates a few seed crystals. These are close enough together so that by capillary action they draw some fluid up into their structure. This wet zone evaporates creating more crystals, which grow partly upward. the wetting and evaporating process continues with the crystals literally pulling themselves up by their own bootstraps.
This process can be demonstrated by placing a tall piece of porous pottery in a dish of growing medium.
The best growth will occur on surfaces that are rough because they have been broken.
Does Vaseline prevent crystals from climbing up the side of the bowl?
Yes. The following picture shows the edge of a dish that had one half of its surface coated in Vaseline.
The area on the left had the Vaseline and shows how it stopped the crystals from working their way up the side of the dish.
Will
the crystals grow without either bluing or ammonia?
Not really. A few crystals may grow but as the following picture shows the clear dish on the left (no bluing) and the blue dish in the center (no ammonia) didn't grow crystals of any significance. On the other hand the dish on the right with the heavy growth had both ammonia and bluing.
I've also tried growing crystals using the same technique but with only salt and water. It didn't produce the large bloom of powdery crystals that the bluing and ammonia create.
Which
works better: just placing the briquette in a pool of the liquid or
spooning the liquid over the briquette?
Spooning some of the liquid over the briquette greatly speeds the creation of crystals. This can be seen in the photo below. The briquette on the left was basted with the liquid and had several crystals after three hours whereas the briquette that was simply placed in the liquid (right) has practically no growth.
Does sprinkling some salt on top of the briquette speed crystal formation?
Yes. Look at the picture above again. The lower halfs of the briquettes were sprinkled with salt. These halves clearly have more crystal growth than the halves that weren't sprinkled.
Which
is the best growing substrate: charcoal briquettes, unglazed pottery
shards, course sponges, fine sponges, cardboard tubes or wet-type
floral foam?
I tested all of these and for reasons I don't understand the briquettes worked the best. Pot shards came in second.
Does
roughening the surface of the briquette or drilling holes in it make
crystals form faster?
Not significantly.
Does
it matter if
the salt used is iodized or un-iodized?
No. While all the other photos in this article are of crystals grown with un-iodized salt, the following picture shows crystals grown with iodized salt. They look pretty good to me.
Does it help to soak the briquette in water for 15 minutes before placing it in the growing liquid?
No. I tried this and the growth started later than briquettes placed in the growing liquid dry or soaked with growing solution. The reason is that before the growing liquid can be drawn up and evaporate to form crystals all the water stored in the briquette has to evaporate first. This takes more time than starting dry and much more than starting with the briquette soaked with growing solution.
Will
growing the crystals with no water work (only ammonia, bluing and salt)?
Yes, but the crystals didn't grow as large or as fast as with some water in the mix.
Will epsom salt work as good as table salt?
I thought it would work better because pure epsom salt crystals are much easier to grow than salt crystals. I was wrong. After three days of growing thee were no crystals at all.
How about sugar?
Again, no. It appears this technique only works with table salt.
Can you dry these crystals to preserve them?
Yes and no. You can dry them but they remain very fragile. Below is an example. The crystals will continue to grow even if the briquette is taken out of the pan of solution because there is a lot of solution still stored inside the briquette.
The simplest, fastest crystals of all to grow
The simplest and fastest crystals to grow are Epsom salt (magnesium sulfate) crystals. Epsom salt is sold for a few dollars in half-gallon containers in the medicine department of grocery stores.
To grow a bowl of crystals, simply mix 1/2 cup of Epsom salt with 1/2 cup of the hottest water you can get out of your kitchen faucet. Stir for one minute and then place the bowl in a refrigerator. There should still be some crystals left on the bottom of the bowl. In three hours the bowl will be filled with needle thin crystals.
This bowl is two inches deep and three across.
Using a narrow deep bowl generates more interesting crystals than a wide shallow bowl. One word of caution: don't boil the water before mixing. If you do the crystals will grow much faster, in as little as an hour, but they will be so fine and numerous that they look like a mass of coarse cotton. Worse still, a hard shell usually grows over the top of the water hiding the crystals underneath.
If you don't have room in a refrigerator, go ahead and bring the solution to a boil for five seconds either in a microwave or over a stove. Stir for one minute (all the crystals will dissolve) and set the bowl out on the counter. In a few hours to overnight, depending on how cool the room is, a bed of fine crystals will form.
The small crystals grown using this technique are very fragile and may be damaged in the process of scooping them out of the bowl. By adding something like a poker chip to the bottom, then dropping a few undissolved crystals on the poker chip, the crystals will grow on the chip and can be removed and displayed more safely.
This one-inch diameter mound of crystals was grown on a disk made of epoxy putty.
Another way to create a display piece is to use tweezers to push crystals taken from the Epsom salt box and push them into a mound of epoxy putty or florist's clay.
Let it, a second bowl, and the bowl with the growing solution cool in a refrigerator for an hour. Then pour the growing solution into the second jar and add the crystal mound. Be sure to not let the undissolved crystals from the first bowl get into the second.
What you'll get after three hours is a tall mound of crystals.
This pile of Epsom crystals is two inches tall.
Unfortunately, food coloring won't color the crystals. A large mass like the one below will pick up a slight tint from dyed water clinging to the crystals, but the crystals themselves remain transparent. Crystallization is, in fact, a very effective method of purification. The crystal lattice determined by the atoms or molecules that make it up is so selective about what it'll allow in that most chemicals are locked out.
Although delicate, Epsom salt crystals are stable and will last a long time. Clusters of crystals like the ones in this article are real dust collectors so if you want to keep them sparkling bright keep them covered except when displaying.
Super-Fast Crystal Spikes
In addition to showing how to grow crystals, I also want to warn people about crystal growing formulas available on the Internet that may be difficult to make work, not because the process is complicated but rather because the formula may be in error or so sensitive that failure is common. This experiment may be one such case.
I found a site that gave the following instructions:
All you need for this demonstration is some Epsom salts, (The stuff people add to water to soak their feet. It's found in the medicine section of grocery stores.) a piece of black construction paper, a little hot water, a pie pan and some sun.
Cut the construction paper so that it lays flat in the bottom of the pan. Mix 1 tablespoon of Epsom salt into 1/4 cup warm water and stir until dissolved. Pour the salt solution over the paper. Place the pan in bright sunlight and as the water evaporates short, spiky crystals will aper. Depending on how hot the day is, the brightness of the sun and the humidity, you can expect to see crystals forming in one to three hours.
Sounds good, doesn't it? The problem is that I've tried it four times and I never got any crystal spikes. I tried varying several parameters and still couldn't get it to work. Perhaps I'm doing something wrong. However, even if this is the case then this apparently simple experiment must not be very forgiving. As such, it may not be the best project to try with young children where you want something that's sure-fire. (If anyone knows how to make this work, I would appreciate an email about how they did it. Thank you.)
I did get it to work very well, though not dramatically, by using table salt instead of Epsom salt. It took 1/2 tablespoon of table salt in 1/4 cup of boiling water. The crystals formed quickly and were easy to see against the black surface of the construction paper. Sugar didn't work... except to attract a horde of ants.
Salt crystals grown in one hour in bright sun: 1/16 to 1/8-inch across
Update: After working with Epsom salt and sugar in other experiments, I learned that the amount of either material that can be dissolved in water is extremely sensitive to the temperature of the water. Take sugar: boiling water will dissolve four times as much as room temperature water. I think what went wrong with the experiment above is that as the black paper heated up, the solubility of the sugar or Epsom salt increased so fast that the solutions remained below the saturation point so there was no motivation to form crystals. Salt, on the other hand, is very weakly effected by water temperature and formed crystals quickly even if only a little water evaporated. Sugar and Epsom salt at high temperatures require that almost all the water evaporate before crystals form. By then the solution is so thick that instead of crystals all that's obtained is powder.
I plan to experiment with this demonstration once the rest of this page is done to see how to make it work reliably. If anyone knows how to do it, I would appreciate an email with suggestions. Thank you.
How To Grow a Washing Soda Snowflake
Mix two cups of water and one-half cup of washing soda - available in the laundry section of grocery stores- in a pot. (Caution: I've heard that a product called Boraxo doesn't work. I haven't tried it so I can't verify this.) Heat the water until it simmers, stirring to dissolve the soap. Pour this solution into a large drinking glass.
Cut a pipe cleaner into three pieces and twist them to form a star. Tie one end of a piece of thread to one leg of the star and the other end of the thread to the middle of a pencil or a second length of pipe cleaner. Make the distance between the pipe cleaner snowflake and the pencil such that when the snowflake is put in the glass the bottom is 1/2 inch above the bottom of the glass. Insert the pipe cleaner snowflake into the washing soda solution and set the glass in a cool location where it won't be disturbed for several hours to overnight.
Pouring the growing solution into the glass after the pipe cleaner snowflake had been added. It works better to fill the glass first then add the snowflake.
If you leave the glass in a cool (50 degrees F.) location, the pipe cleaners should be completely covered with crystals in 8 to 12 hours. Pull the snowflake out carefully, the washing soda crystals aren't as delicate as Epsom salt crystals but they will break off.
This snowflake crystal is two inches across.
Check the status of the crystal every hour until the crystals start growing, then more often until you get the size of crystals you want. Left too long, the crystals will grow to the sides and bottom of the glass making a solid mass. If this happens, try using a sharp knife to free the snowflake. Work carefully and slowly and you should be able to pull it out. Then break off any chunks of crystal which ruin the snowflake shape.
Washing soda crystals incorporate a lot of water into their structure. If you leave the snowflake out this water will begin to evaporate turning the crystal a powdery white.
Dried out it looks more like a snowflake but a little less like a crystal.
The incorporation of water into the crystal matrix explains an interesting aspect to washing soda crystals: the amount of crystal you get out is much greater, both on volume and weight, than the amount of washing soda you mix into the water. You can demonstrate this by letting a glass of the solution completely crystallize. The amount of water that can be poured off afterward is only half of the two cups originally used. The crystals in the glass will fill the bottom half. Crush fresh washing soda crystals and they smush (technical term known by all elementary school students) into a slushy mixture of water and crystals.
If you are in a hurry you can place the glass in a refrigerator and it'll only take three hours or less for the snowflake to form. Be careful to check it often because under these conditions the crystals grow very fast.
You can also experiment with forming the pipe cleaners into different shapes and adding food color to the solution.
The coloring in the picture above is on the crystals, not in them. As crystals grow, their structure is so rigidly determined my their chemical makeup that any non-compatible atoms or molecules, like dyes, are excluded.
A super-fast crystal growing technique that really works
Washing soda crystals are perfect for a super-fast demonstration of crystal growth. Simply set up a drinking glass for growing a washing soda snowflake but don't insert the pip cleaner snowflake. Instead, cover the glass with a piece of saran wrap so that surface evaporation doesn't trigger crystal growth. Let the glass cool for four hours to room temperature. If no crystals have formed spontaneously you should be set. If they have but are small, you can still proceed. But if they fill up the glass you'll need to start over. The next time be careful to keep everything clean. Dirt can provide sites for crystal formation.
I've heard than shaking super saturated solutions can cause them to start forming crystals so once the glass is full of the hot mix, be careful to avoid disturbing it.
If everything has gone correctly you should have a glass full of super-saturated growing solution that's desperate to grow crystals. The problem is that until it gets a seed crystal to get started, it can't do anything. Take a straight pipe cleaner and wrap one end around a pencil so that the tail hanging down won't touch the bottom of the glass. Uncover the glass and dip the pipe cleaner in the solution to wet it. Pull it out, sprinkle a small pinch of washing soda on the pipe cleaner being careful not to get any in the solution, then put the pipe cleaner back in the glass. The washing soda will provide lots of seed crystals and the solution will jump at growing crystals on them. In as little as 20 minutes the entire glass will be filled with crystals.
On the day I took the following photos, the temperature was a little warm for supper-fast growing. Still the results are impressive when compared the the days to weeks required for many crystals.
After ten minutes
After 20 minutes
After 30 minutes
After 40 minutes
The length of the crystal column above is four inches and the width of the crystals at the bottom of the last picture is three inches.
Had the temperature been ten degrees cooler, say 50 degrees, the time to get from inserting the pipe cleaner to getting a crystal mass the size shown in the bottom picture would have only been 15 minutes. Also, every time I removed the cluster to take a picture, it slowed the growing process significantly.
This closeup of washing soda crystals shows their flat planar structure.
Note: I received an email from Mr. Randy Oliver of the Nevada County Science Center, California, who explained that washing soda and borax are not the same chemical. Washing soda is sodium carbonate, borax is sodium borate dodecahydrate.
I repeated the experiment above with borax and found that the crystal grow shows up as small, uninteresting grains and does not get as large as those grow with washing soda.
Soap Crystals
I found the following procedure on the Internet and decided to give it a try. Because much of the growing medium is liquid soap, I'm calling it, "soap crystals," even though the crystals are more likely alum or salt. The only attribute I have for this procedure is that it was sent to the site from someone with the email address: Gray-goose@webtv.net.
Mix a solution of:
1/4 cup of liquid Cheer
1/4 cup of Ultra Joy (antiBacterial)
1/4 cup of salt
2 Tablespoon (15 ml) ammonia.
-pour it in an aluminum pan and place a sponge in the mixture. Sprinkle alum on one end of the sponge. Place it in the sun and a crystal bloom similar to the salt/bluing/charcoal briquette technique mentioned earlier .
I tried this experiment and only got a little blooming near the edge of where I'd sprinkled the alum.
The results were so unimpressive that I can't say it was worth the effort. But, the problem probably is that I did something wrong. The site:
http://www.rockhoundingar.com/pebblepups/growcryst2.html
has the original article on this procedure with pictures of what the crystals are supposed to look like. (If anyone knows how to make this work, I would appreciate an email about how they did it. Thank you.)
How to grow stalagmites and Stalactites
If you have a hard time remembering which is which, just remember this: To hang from the roof of a cave, stalactites must cling "tite" to the ceiling. So, stalactites hang down, stalagmites grow up.
In real caves, water seeping through rocks dissolves many minerals including calcium carbonate. When this water slowly drips from the roof of a cave, each drop deposits an small amount of calcium carbonate as it hangs for a moment before falling to the floor. Over centuries these deposits lengthen to form stalactites. When the drop hits the floor of the cave and evaporates, it leaves behind the rest of the calcium carbonate. In time these deposits grow up forming stalagmites.
At home or in a classroom this process is much too slow for demonstrations. But, by switching to concentrated solutions of washing soda or Epsom salt, both of which are much more soluble in water than calcium carbonate, it's possible to grow a two inch long stalactite in as little as four hours. Here's how:
Bring four cups of water and one cup of washing soda to a simmer, stirring until all the powder dissolves. Divide this solution into two large drink glasses set four inches apart on a cookie sheet with an edge that can prevent liquid from escaping. Take a 12 inch long piece of heavy yarn and tie a small metal washer or nut to each end. Dip the yarn into one of the glasses to get it completely wet then suspend the yard between both glasses with one end of the yarn in each glass. Adjust the spacing of the glasses so that the bottom of the loop of yarn is even with the level of the growing solution in each glass. Cover each glass with a piece of saran wrap, being careful not to press down on the yarn. (The saran wrap prevents evaporation that could cause crystals to form on the surface of the glasses.)
Capillary action causes the solution to be drawn up the yarn and over the edge of the glass. Then gravity pulls the solution down to the lowest point of the hanging loop and causes it to drip off. If the dripping is slow enough, each drop with leave behind a deposit of washing soda, forming a stalactite. Move the glasses closer or further apart so that the drip rate is one drop every five to ten minutes.
The following pictures show the growth after two, four and eight hours:
The photo above was taken two hours after starting. Instead of glasses I used glass bread pans because I wanted to test different materials to grow the stalactites from. The blue line in front is thick yarn. The one in the rear is a 1/2 inch wide piece of terry cloth. Both worked well. The yarn started off faster because its loop hung a little lower than the terry cloth. I also tried a piece of fleece but quickly discarded it because it pumped so much liquid I couldn't control the dripping.
After adjusting the bread pans so that the terry cloth strip was slightly lower than the yarn its stalactite quickly caught up and passed the yarn. The picture above was taken after four hours of growth.
After eight hours of growing.
I also tried a mixture of four cups of hot water and two cups of Epsom salt but the stalactite didn't form as fast and had a transparent appearance that didn't look right. Additionally, the stalactite that formed was much more delicate than the ones grown using washing soda.
The Epsom salt stalactite crystal above is an inch and a half long and took eight hours to grow.
If you plan to grow a long stalactite it'll be necessary to move the glasses closer together every four hours or so. As the liquid is drawn up out of the glasses, the level of the solution drops, slowing the drip rate. Keep adjusting the distance between the glasses so that the drip rate remains at the optimum growth rate for your particular setup.
One of the things I learned was that the diameter of the stalagmite is influenced by how far the drop falls before hitting it: the further the fall - the larger the diameter. In the picture above the stalagmite started off with the drops falling six inches. After eight hours I reduced the fall to 2 inches while keeping the drip rate the same. The shorter fall made the stalagmite grow tall faster but narrower. The bottom of the stalagmite in the picture is 1/2 inch in diameter. The narrower top section is 1/2 of that.
I found that placing a piece of absorbent cloth where the stalagmite will form helps give it a more definite shape than when the drops simply fall on a nonporous surface.
Salt Crystals
While easy, this technique does not impressive crystals. Mix 1/4 cup of table salt into 1 cup of water, let it rest one minute, stir again and let any undissolved salt settle. Pour the solution, but not any remaining salt particles, into a Teflon lined pan and set it in the sun. After two hour you should see a scattering of salt crystals growing on the bottom of the pan. (Teflon pans work best because their dark color absorbs more heat from the sun and therefore speeds evaporation.)
The square salt crystals are 1/16 inch across.
Also look at the edges of the pan. Many times there will be thin sheets of clear material growing down to the water. These are crystals growing right at the edge of the water as it evaporates. As the water recedes, the crystals as forced to grow in thin sheets.
There are two problems with this procedure. First, the crystals are small. I've tried using different types of salt and water and growing them very slowly but they don't seem to like getting larger. When I place a large seed crystal into the solution, instead of growing larger it gets covered with many small crystals. Second, white powdery islands of salt form on the surface of the liquid that fall when disturbed hiding the crystals growing on the bottom.
If you can spend a day waiting for crystals to develop, you can get a much better display by dissolving 1/2 cup plus 2 teaspoons of salt in two cups of water, heating slowly and stirring just until the salt dissolves. Avoid bringing the liquid to a boil.
Pour this solution into a tall glass and dip a weighted nylon thread into it, pull the thread out and suspend it somewhere to dry while the salt solution cooled. Once the salt solution has cooled to room temperature, suspend the dried nylon thread back in it and cover the glass with a piece of cloth. By the next day there should be long thin spikes of crystals growing up at every possible angle from the bottom of the glass. There should also be thousands of crystals growing out from the nylon thread.
This picture is enlarged. The
largest crystals visible are only 1/8-inch long.
If you grow these crystals, be
sure to shine a bright focused flashlight
through the jar from the opposite
side you're looking from. You'll be
able to spot hair-thin crystal
threads extending far out from the
nylon thread.
The pile of crystals growing up from the bottom of the jar formed very interesting shapes. Unfortunately, while the individual crystals are quite tough, they don't stick together and as a result the mass of crystals falls apart easily when you try to pick them up.
This is a single salt crystal
harvested from the bottom of the glass.
It's small, only half an inch long.
Vinegar/salt garden
This was another dud for me. Following the instructions in a book from the library, I combined 1/2 cup of warm water, mixed in salt one teaspoon at a time until no more would dissolve, added 1 teaspoon of vinegar and poured this mixture into a plastic tub. Then I added a charcoal briquette and waited. After a day with no results I placed it outside in the sun and gave it another day. Still nothing. Here's what it looked like after the two days:
Bicarbonate of Soda Crystals
You can grow crystals, sort of, from plain old baking soda or more properly bicarbonate of soda. Mix 3 and 1/2 teaspoons of baking soda in 1/2 cup of water. Heat gently and stir until all the soda dissolves. Do not bring to a boil. This is tricky because as the baking soda warms up it releases carbon dioxide gas, which looks like bubble from boiling.
Pour this mixture in a glass and let it cool. After several hours you should see a fine layer of crystals growing on the sides and bottom of the glass. The individual crystals are tiny so I rate this as a poor demonstration of crystal growth.
This is a closeup of the small
grainy crystals grown from baking soda. There
is one interesting feature. Note
the oval fan-like growth in the upper
center. It's reminiscent of the
snow crystal fans observed in the
water crystal growing section
further down this page.
Advanced
crystal growing projects
The following crystals require more exotic chemicals or more elaborate procedures than the experiments above.
Rock Candy
I found more errors in the formulas available on the Internet for making rock candy than any other crystal growing technique. Many of them advise boiling a sugar and water mixture until it reaches the hard ball candy stage then letting the crystals grow for a week. If you do that the crystals will completely fill the growing container and be impossible to remove. This, and several other gross problems with using crystal growing formulas that failed, makes me suspect that many of these formulas are being recommended by people who have never tried them.
The following formulas are ones I have personally used.
Fast
growing but small crystal size rock candy technique
Warning: the following procedure requires boiling a sugar syrup. Hot sugar syrup can stick to skin and cause severe burns. Only do this with adult supervision, preferably someone experienced with hot-sugar based candy making.
Bring one cup of water and two and one half cups of sugar to a steady even boil (half way between a summer and a rolling boil) and maintain it for about half an hour until the syrup reaches 250 degrees F., or the hard ball stage. Pour this into a tall heat proof glass container and dip a long wooden skewer into it. Remove the skewer and let it air dry while the syrup cools. (Dipping the skewer and then letting it dry creates a coating of seed crystals on it that will facilitate crystal growth. Also, be sure to remove the sharp end of the skewer so no one gets poked with it.) Cover the syrup container to prevent evaporation from forming crystals on the syrup's surface. Let the syrup cool fifteen minutes and then suspend the skewer down the center so that the bottom of the skewer is one inch above the bottom of the container. (One way to hold the skewer in place and keep the container covered is to poke it up through a clean plastic butter container cover.)
Now sit back and watch the show! In as little as ten minutes you will be able to see crystals forming on the skewer and all through the syrup. After half an hour the glass should look like the picture below:
This is the best time to remove the skewer and suspend it in an empty glass to let the syrup drain off. The syrup is thick and will take a couple of hours to drain and dry up. Be careful, even an hour after boiling the syrup can still be very hot.
The crystals grown using this technique are much smaller than those commercially produced for rock candy, think gravel instead of rocks.
If you wait much longer than an hour to remove the skewer you run the risk of having the crystals lock up so tight in the glass that you can't remove them. Waiting longer will not allow the crystals to grow large like the ones you see on strings in candy stores. Those are grown much slower. In crystal growing, fast growth almost always means small crystal size.
Caution: if the crystals are allowed to sit overnight, those growing on the bottom of the glass will adhere to it so strongly that they are almost impossible to get loose. Repeated soakings in hot water helps, but a better solution is to use a disposable glass... just make sure it's heat proof.
For making several small samples, stick toothpicks through a soft plastic cover and place it over a wide shallow glass. Crystals will grow on the toothpicks.
These were grown in water with green food coloring.
I also tried this experiment with syrup cooked to 240 degrees. It behaved the same as the 250 syrup except it took an extra hour to develop the crystals and they weren't quite as dense.
I experimented this crystal growing procedure up after boiling the sugar syrup to 215, 220, and 225 degrees F. The goal was to see if there was an optimum temperature at which large crystals formed quickly. After two hours the 215 degree sample showed no growth. The 220 degree sample had a few small crystals and the 225 degree looked like this:
Note the free floating crystals.
Two hours later the layer of crystals had doubled in thickness. There was no change in the other two test cases.
After 24 hours the 225 degree syrup stopped growing and looked like the picture below.
The 220 degree syrup after 24 hours had similarly stopped growing and only had a few tiny crystals.
The 215 degree syrup showed no growth at all.
From this I assume that the optimum syrup temperature for growing small fast sugar crystals is between 230 and 235 degrees.
I tried an experiment to grow larger crystals by slowing down the speed that the sugar syrup cooled. To do so I placed the glass containing the syrup inside two Styrofoam chests. The smaller chest was covered with aluminum foil to reduce heat loss do to thermal radiation.
While I boiled up a batch of 230 degree sugar syrup, I heated the glass and 20 pounds of iron weights in the oven to 230 degrees. Once the syrup was ready, I poured it into the heated glass (heating the glass prevents a sudden temperature drop in the syrup) and placed the glass and iron weights in the insulated boxes. The weights act as a thermal ballast to keep the temperature from dropping too fast. The boxes were placed in the back of a closet in the center of the house where temperature variations are minimal. Thirty-six hours later the crystal mix had lost all its heat and I opened the box to find a beautiful cluster of much larger sugar crystals clinging to the skewer.
Many of the individual crystals showed the classic elongated hexagon shape of sugar crystals.
These crystals are getting close to the size of those grown commercially in the manufacture of rock candy. I suspect that if I increased the thermal mass and the amount of insulation to slow the growth, the crystals would become even larger.
The next step was to repeat this last experiment, but this time instead of inserting a stick on which to grow a cluster of crystals, I inserted a single large seed crystal to see how large it would grow. It didn't. Instead, all I got was a solid mass of small crystals packed around it.
Rock Candy on a String
This is the classic way rock candy is grown and sold. I tried making it by filling a glass bread pan with 115 degree syrup and laying a length of yarn in it. After covering it with a cloth and placing it in a safe (ant-free) location for two weeks I went to check and discovered two things: the liquid had formed a hard shell over its surface preventing the evaporation that was supposed to drive crystal formation and the crystals on the yarn were very small. Complicating things further was that the yarn had gotten so attached to the crystals growing on the bottom of the pan that it broke when I tried pulling it loose.
My second attempt was to start with room temperature water, in which as much sugar as possible could be dissolved (In my case, 4 cups of sugar in three cups of water at the temperature of the growing location left a small amount of undissolved sugar on the bottom of the mixing jar after three stirrings and rest periods. This is perfect because a little undissolved sugar is a guarantee that the solution is saturated.) After pouring the saturated solution, but not the undissolved sugar, into a glass bread pan I placed a length of cotton string (not yarn this time - I decided fuzzy rock candy wouldn't be to appetizing) in the liquid and suspended it with a wire holder at each end so that is was an inch off the bottom of the pan.
The setup sits in a shallow pan
filled with a 1/8-inch thick layer of oil to keep
ants out of the sugar solution. If
there's one thing that'll draw them it's
concentrated sugar water sitting
undisturbed for weeks at a time.
How'd it turn out? It didn't. After a week nothing had formed on the string. I even tried dusting the string with sugar crystals and still couldn't get anything to grow. After experimenting with sugar solubility I discovered that I hadn't managed to create a saturated solution.
I've made three observations that suggest that evaporation is not an important factor in growing sugar crystals. First, I dipped a nylon thread into a 190 degree sugar syrup (very thin) and let it air dry to create nucleation sites of crystals. After 24 hours the tiny droplets, less that 1/100th of the size of a drop of water, were still tacky, indicating that in spite of their small size they still had not dried out. With an evaporation rate this slow it's unlikely enough water would evaporate from a growing solution to cause crystallization at a fast enough rate to form crystals within a reasonable number of weeks. Second, after spreading a thin layer of the same sugar syrup on a plate and letting it rest for several days, I noticed that a very thin hard shell had formed on the surface. Although the first experiment showed evaporation was very slow, this proved that it nonetheless happened. But, the syrup under the shell was still thin and liquid. Evidently some small amount of evaporation will occur to form the shell, then the shell blocks the air from getting at the remaining syrup and further evaporation is stopped. Third, I set up a 215 degree syrup and let it sit for a full month. After an initial small precipitation of crystals over the first 24 hours followed by the formation of a hard shell across the surface, there was no additional crystal growth.
I believe that these observations indicate that almost all sugar crystal growth beneath the surface of the is strictly the result of precipitation out of a supersaturated solution and not from prolonged evaporation.
What all of the above showed me was that growing large sugar crystals is tricky and almost certainly requires a thermostatically controlled growing chamber capable of handling 230 degree F. temperatures. These are available at most laboratory supply stores for five hundred dollars... or you can do almost as well by looking in your pantry: a crock pot. Since this is getting complex I'm going to continue the saga of my search for a technique to grow large sugar crystals in the Growing large, high quality single crystals article below.
Two
important hints about working with sugar solutions:
You can color sugar crystals with food coloring. BUT! add the food coloring before you boil the syrup if you are using a technique that requires a concentrated syrup. If you try adding it afterward the liquid coloring will flash to steam creating a cloud of bubbles and the syrup will crystallize solid in a few minutes. Also, never add cool liquids to hot syrup. There's always the chance that when the cool liquid hits the hot syrup it could boil and splash you with syrup hot enough to burn.
The counter area near where the syrup was boiled will be splattered with tiny drops of sugar syrup. Unless you want legions of ants swarming through your kitchen I recommend you follow this experiment with a thorough cleaning.
Alum Crystals
Alum (aluminum potassium sulfate) can be purchased in the spice section of larger grocery stores. It's used in pickle making to make the pickles crisp. In crystal growing is is celebrated as one of the easiest chemicals to use for growing large, clear crystals. It naturally seems to prefer to to grow a few large crystals over many small ones.
Mix two tablespoons of alum in 1/2 cup of water. Heat and stir until the alum dissolves. (A good way to see if it's dissolved is to stir in a circular pattern then pull the stirrer out. As the water swirls around any undissolved crystals will collect in the center of the pan where they are easier to see.)
Pour this solution into a clear cup and set is aside for 24 hours. By that time the bottom should be covered with crystals.
Alum crystals after the growing solution has been poured off.
Some of the better individual crystals collected from
the glass above.
Many of these would make good seed crystals.
Alum's desire to form single crystals can be seen below.
The same growing solution used in the first alum grown above was used here. The only difference is that instead of letting the mixture cool down quickly, it was placed in an insulated box so it would cool slower and the crystals would grow slower. Usually this results in a solution forming dozens of medium crystals instead of hundreds of small crystals when the fast cooling technique is used. I alum's case, only four very large crystals formed. Granted, they are all badly flawed, but to get so few out of an uncontrolled crystallization is amazing.
Growing Crystals in a Gel
I read about this in a book from the library and thought it would be a way to grow crystals without having to tie a string on them to suspend them in a growing solution. I tried it and while it works the quality of the crystals is so poor I can't recommend it.
Mix 1/2 cup cool water with two tablespoons of alum in a non-aluminum sauce pan. (Teflon coated is okay.) Sprinkle 1 teaspoon of plain gelatin over the top of the water and let it soak for 5 minutes. Then start stirring and warming the solution until it comes to a simmer and all the gelatin is dissolved. Pour this solution into a glass and let it stand for 24 hours. By then you should be able to see white lumps growing in the cloudy gel.
These lumps are the crystals. The problem is that the gelatin interferes with the crystallization process so they come out irregular and cloudy, as show below:
(If anyone knows how to make this grow good quality crystals, I would appreciate an email about how to do it. Thank you.)
I found a
webpage explaining a complicated procedure for growing crystals in
gels. It is: http://k12s.phast.umass.edu/k12/brown/gelxtals.doc.
Ultra-fast sheet crystals
These technique produces crystal grow on the order on one inch per second. It is by far the most dramatic example of crystal grow.
Prepare your favorite growing solution. While it is still warm, pour a small quantity in the bottom of a warm metal pan. (You don't what the solution to boil when it hits the pan. The warmth is only to speed evaporation.) Swirl the solution around to form a very thin layer then set the pan down a watch. Within a minute or two crystal fans will spread across the face of the pan with startling speed.
The process just starting. In this
example I used monoammonium phosphate with green dye.
This works well with almost any
crystal growing mixture.
This picture was taken only five seconds after the one above.
Monoammonium phosphate crystals
Monoammonium phosphate is one of the two chemicals sold in crystal growing kits because it is second only to alum (the other found in kits) in being the easiest crystal to grow.
Mix six tablespoons of monoammonium phosphate into 1/2 cup of water. Heat slowly and stir until it's completely dissolved. Pour this solution into a glass. Twenty-four hours later you should have a thick bed of long thin crystals growing in every possible direction.
If the solution is allowed to cool more slowly in an insulated box, I use a Styrofoam ice chest with a pot of hot water in it to slow the cooling, much larger crystals will form in a truly impressive display.
This cluster of crystals is 2 and 1/2 inches across.
Growing
large, high quality single crystals
Tricks
of the trade: hints on how to grow the
best crystals.
Growing high quality single crystals is the ultimate challenge for the crystal grower. It requires careful attention to detail, temperature controlled growing chambers (surprisingly easy and inexpensive to make), and patience. Failure is more common than success but the rewards are worth it. Nothing either man made or natural is more perfect than a single crystal. Even a small one represents billions of atoms or molecules arranged in perfect order. The fact that anyone can grow such perfection in their own kitchen is amazing.
(The following articles apply to growing any crystal.)
Seed
Crystals:
The first step in growing an outstanding crystal is to grow an outstanding seed crystal. Most references recommend growing seed crystals by evaporating a saturated solution until single crystals form on the bottom of the bowl and then tying these at the end of a thread, which is then suspended in a growing solution. The problems with this technique is that it's common for the seed crystal to slip out of it's knot and fall to the bottom of the growing jar. Even it it remains and grows a large crystal, the loop and knot that went around the seed will be visible. Worse still, seed crystals grown this way tend to be hazy. Because the surrounding crystal will be optically clear the hazy seed crystal will stand out in the heart of the gem you're trying to grow. As a flaw, it will draw the observer's eye away from the good part of the crystal.
My solution to these three problems is challenging, but results in superior crystals.
First, prepare a growing solution and tie several nylon threads to a pencil with weights on their ends so they hand down into the solution. Wait a day to see if and crystals start forming on them. If they do, then you are off to a good start. If not, pull the threads out of the solution and let them air dry for half an hour then put them back in. This will create microscopic seeds on the threads which will act as mini-seeds for the seed crystals you want. After an hour your threads should look like this:
These seed crystals are 1/32-inch across.
Now comes the tricky part. Pull the threads up and gently use your thumb and forefinger to pinch the crystals several times all the way down the length of the threads. Crystals growing on the surface will break loose. Crystals growing all the way around the thread will remain. Dip the thread a couple of times in the growing solution to rinse off loose crystals. Repeat this step if necessary until only a few crystals remain. If you are lucky you will end up with a thread that has three or four good seeds growing on it.
Put these back in the growing solution to get larger. Once they are around 1/8th inch across, they will be perfect for starting a crystal. The great thing about these seed crystals is that because they've grown around the thread they can't come loose and fall off. As they grow, you can slide them up and down the nylon thread to accommodate changes in the level of the solution.
When you put the seed crystals back in the growing solution to get larger, it's common for more crystals to form on the threads. These develop on the residue of the crystals you removed. You can prevent almost all of these by using a narrow, steady stream of warm water from the kitchen faucet to wash the thread off between the seeds you want to keep. This takes a steady hand otherwise you're likely to wash away the crystals you want to keep.
The best thread to use for crystals is transparent nylon. It's invisible in the crystal and best off all, seed crystals slide up and down it so they can be positioned to the most convenient location for growing. As it comes off the spoon it will often be so curly it's difficult to work with. To straighten it, simply give a length of it a firm pull. The thread will stretch a little and in so doing straighten out. When tying knots, working over a dark cloth will help you to see the nearly invisible thread.
Accidents happen, parasitic crystals form on main crystals, and crystals break. For these and other reasons it's best grow several crystals at a time in the same jar. That way if something happens to one you can remove it and carry on with the others.
Starting
your crystal:
Regardless of whether you elect to grow your crystal by the evaporation technique or the super saturated technique, you will need some way to suspend the crystal in the growing medium. Many references suggest hanging it from a pencil laid across the top of the growing jar. The problem with this is that where the thread meets the liquid is a prime location for the growth of crystals. These can break loose and fall down on the main crystal, start to grow, and ruin it. A better technique is to bend a length of wire into a small loop, which will act as a base to rest on the bottom of the growing jar, and then bring one end up and over and form it into a hook. The crystal is tied to the hook and hangs down. Because the entire unit is below the surface of the growing solution there is no place for secondary crystals to form and fall on the primary crystal. This is a good technique with only one weakness.
As crystals grow, they pull molecules out of the growing solution. The solution is now lighter so it rises. The top half of the crystal is caught in this wash of less concentrated solution so it grows slower than the bottom half. The result is that the crystal grows lopsided. If there is anything as bad as a crystal with internal defects, it's one that's nonsymmetric.
To solve this problem I use a growing frame that can be turned upside down from time to time so that both the top and bottom grow at the same rate.
A sample of my growing frame with a seed crystal tied at both ends. It's
an inch and a half across and the same tall. The thread is
transparent and almost invisible in this picture.
Using a growing frame like this isn't necessary to grow good crystals, it just helps a little. I've gotten perfectly acceptable crystals from seeds attached to a thread that's simply dangling in the solution.
If you prefer to use the suspension technique, rather than hanging the crystal from a stick resting on the top of the growing jar, may I suggest that you visit a office supply store and look for wire cloths pins. When one leg is bend back ninety degrees, the cloths pin can be clipped to the lip of the glass and will stay in place much better than a stick just resting on the lip.
The bent leg extends out to the middle of the glass in perfect position to hold the line on which the crystal will grow. I don't tie the line to the overhanging leg, but rather tape one end to the side of the glass and then simply drape the line over the loop. This way I can pull the line up to work the crystal without having to remove the clip.
Growing techniques:
One of the two ways to grow a crystal is the slow-cooling technique. The growing solution is heated to dissolve a large amount of chemical then slowly cooled to the point where there is more chemical dissolved in the liquid that the liquid can hold. If a crystal is introduced at this time it will grow very rapidly. Usually this technique works so fast that many small, flawed crystals are formed. To grow a high quality single crystals it's necessary to have the solution in a sealed jar in an electrically heated water bath inside an insulated box. The temperature is then reduced very slowly (one degree F. per day) so that the crystals have time to form with as few flaws as possible. This technique works well and can produce large crystals in as little as two weeks. The problem is that it takes a lot of equipment and has to be worked with every day. The hazard with this technique is that it is very easy to loose control of the crystal growing rate and wake up with all sorts of ugly things growing on your main crystal.
This one got away from me while using the slow-cooling technique.
It's clouded and irregular.
Even with this technique, parasitic crystals can still form on the surface of the main crystal. Opening the jar to remove them can start the formation of many other unwanted crystals.
The evaporation technique is much simpler and cheaper. The cost for this is that it is also much slower. To do it you warm the growing solution to dissolve more chemical in it than it can hold at the temperature of the growing location. The solution is allowed to cool and a few loose crystals are added. Twenty-four hours later any extra chemical that was in solution that can't be maintained in its dissolved state because the temperature is too low will have formed on the seed crystals. You now have a saturated solution. Pour this into a clean dry glass, add your good seed crystal, cover it with a cloth to prevent dust falling into the solution and forget about it. As the solution evaporates it becomes slightly supersaturated and the excess chemical will form on the main crystal. Because evaporation is slow the crystal will grow slowly insuring a high quality.
Take a look every day to make sure no small crystals have formed on the main crystal. If so, pinch and rinse them off using the same technique used to grow the seed crystal. Other than that, simply watch the crystal grow. If the solution is clear, you should be able to see growth within the first 48 hours. Once the crystal gets to be 1/2 inch across the growth may appear to slow down, but it hasn't. It's just an optical illusion. A growth rate of 1/64-inch per day is easier to spot in a small crystal than it is in a large one.
Whether you use the super saturated or evaporation technique, the best location for your setup is somewhere with the least amount of temperature fluctuations: usually a closet located in the center of the house. Placing the crystal growing solutions on a shelf at eye level makes observing easier and more enjoyable. Growing them in a thermal bath, a fish tank with a thermostatically controlled heated, is the ultimate but may be too much expense and hassle for some. I've gotten good results with the evaporation technique without it.
But for expensive crystals and during times of the years when temperature changes make good crystal growing difficult, I use the growing tank pictured below:
By insulating the tank with foam, daily temperature
changes are almost completely eliminated.
Crystal surgery:
If a second small crystal starts growing on either a seed crystal or your main crystal, you can either ignore it and hope that the larger crystal will grow over it or take the more hazardous choice of removing it. Usually a fingernail will usually dislodge the offending crystal. The problem is that it sometime leaves a crater in the main crystal. This will heal but it may leave a defect that looks like a faint fracture. I've experienced good and bad results from both techniques.
Harvesting and storing crystals:
When a crystal is removed from its growing solution it will be wet. If it's allowed to air dry the liquid will evaporate quickly and may form many microscopic crystals on the surface of the main crystal. This can dull the shine. I recommend drying crystals with a very soft tissue like Kleenex the second it's removed from the solution.
Some crystals, like alum, are very stable and will last for decades as long as they are kept away from moisture. Even occasional handling hasn't hurt mine. Other crystals may dehydrate and are trickier to preserve.
..
................. 
....
......nickel
suflate hexahydrate...nickel
sulfate heptahydrate after 2 days
As the above pictures show, some crystals, like nickel sulfate heptahydrate, quickly dehydrate, forming a white powder on their surfaces. Several coats of a clear gloss spray paint may slow the process. The risk is that before it dries the paint may dissolve part of the crystal or worse, the chemicals in the paint may react with the chemicals in the crystal. This method also has the drawback that the many coats may dull the sharpness of the edges of the crystal, reducing its attractiveness. I've had some luck preserving crystals using a gloss protector for photographic prints. One way to preserve crystals that dehydrate that was recommended by a couple of crystal growing sites I've visited is to place the crystal in a jar with a sponge saturated with water. The crystal goes in a small cup inside the jar so that it doesn't come in contact with the wet sponge. I tried this and it didn't work. The humidity in the jar was so high that the crystals started to melt.
My preferred preservation technique for crystals that dehydrate is to store them in a tightly sealed jar that is filled with small trash and seed crystals of the same type. The atmosphere in the jar quickly adjusts to the perfect humidity for preserving the crystals. Using this method I've kept nickel sulfate crystals, which dehydrate quickly, in perfect condition indefinitely.
Amount
of solution needed to grow good crystals:
A crystal of alum that measures an inch from tip to tip only weighs three grams. Since a tablespoon of alum weighs 14 grams and will dissolve in 1/4 cup of warm water, it's easy to see that a lot of solution isn't required to grow a nice sized crystal. More often than not, people mix up far more than they need. This isn't necessarily wasted. Extra solution allows for maneuvering room if you have to move the crystal around. It also provides some thermal ballast to blunt sudden temperature spikes. What I'm saying is that one cup of solution is enough to grow most crystals. Two cups may provide more elbow room but really aren't needed. This can be valuable information if you're growing a crystal that requires expensive chemicals.
Since a little solution is more than enough for a good sized crystal, consider growing several crystal at the same time. That way if something goes wrong with one, the others can take it's place.
Fall
is
the best season to grow crystals by the evaporation technique.
Why? Because the slowly decreasing temperatures help keep the growing
solution supersaturated. Late Spring is the hardest time of the year
to grow crystals because the increasing temperatures can drive the
growing solution toward undersaturation faster that evaporation can
drive it toward supersaturation. The result is that a crystal that
grew fast in March may actually decrease in size during April. It's
times like that when I fire up my heated growing chamber.
Are
your crystals shrinking?
Because crystals grow so slowly this can be a tough question to
answer. The key is to look at the sharp corners of the crystal in
question. If they looks razor sharp and well defined the odds are
excellent that the crystal is still growing. If they looks dull or
rounded the crystal is most likely dissolving, usually because the
temperature has increased slightly and the growing solution has
dropped below the saturation point.
What to do? First, I remove and dry the crystal. Then I warm the growing solution ten degrees F. warmer than the highest temperature the room in which the crystals are growing is likely to get to dissolve some of the crystals laying on the bottom of the jar. After that I place the jar in a water bath maintained at a temperature five degrees