Introduction: Crystal Growth Project
Growing crystals is not a long or complicated process. In fact, it's easy, fun and educational. In this example, we've dissolved Potassium Alum in water and within hours we'll be able to see sparkling crystals grow right before our own eyes.
Discover the laws of nature which creates crystals deep inside the Earth. Get a better understanding of how astronauts grow ultra-pure crystals in the weightlessness of space, and create your own collection of large crystals clusters, geodes and gem-like single crystals. A fascinating experience for children and adults!
Step 1:
Begin by making a saturated solution of Potassium Alum (salt). Dissolve 100 grams of the Alum in 500 mL of hot (near boiling) water. Slowly stir your solution until all of the crystals have dissolved.
Step 2:
Allow the solution to cool down (20-30 minutes). While you are waiting for your solution to cool down, this is a good time to prepare the string that the crystals will grow on.
Tip: We noticed that when we used a thin rubber band as a string, we were able to pull the crystal right out after it had formed the next day and therefore had a crystal specimen without any string or bands connected.
Step 3:
To give the crystal color, you can add some food dye/coloring.
Step 4:
When the saturated solution of Potassium Alum has cooled down to room temperature, carefully pour it into a clean beaker or glass making sure that no undissolved or crystallized salt gets transferred during the process.
We've used a coffee filter to make sure this process is done properly.
Step 5:
After transferring the solution and filtering all visible crystals, sit the dowel with string on top of your beaker or glass with the string immersed in the solution.
Step 6:
Cover the beaker with a napkin because crystals will form on practically anything that gets inside the cup.
Step 7:
As the water begins to evaporate, the salt will begin to form crystals on the string. It may take a few hours or even up to a day to see crystals so be patient and observe it periodically.
There are many factors, such as temperature, amount of Alum/Water used that will determine the size of the crystals. Test them out and see what crystals you can make! To purchase Potassium Alum, you can visit ScienceKitStore.com and type "Potassium Alum" in the search option.
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30 Comments
3 years ago
its good idea but
i need more ideas
6 years ago
wow
\
7 years ago on Introduction
If you want a nice, single-crystal (basically an ocaedron), this is the basic technique (1st semester chemistry stuff =) ): make a hot solution, let it cool, separate (via magnifying glass and spatula or something), get the crystal nearest looking to an octahedron and put it on something to hang in a new, warm, saturated solution of your salt. we used hair (poor blond, long haired girls in those times :D ) and made a knot around the mini-crystal). grats, you now have a initial growth-crystal. let water evaporate and/or cool down will rather grow your single crystal rather than forming other crystals on somewhere in the glass.
also: the slower the crystal grows, the cleaner (and prettier) it gets. best way (imho - in the case "oooh i want a shiny crystal" - not getting XRD-crystal-meassureable ones) is to make the hot solution in a beaker by putting the beaker in a hot water bath (e.g. a pot of water), filter it into another beaker, put the new beaker into the hot water bath, put some kind of a lid (those glass lenses, i dont know the english word, but in german its "Uhrglasschale") on it, turn of the heat and go away for 3 days. -> slow evaporation, slow cooling -> big nice crystals.
another way is to take a glass container, (eg. 25ml with plastik cap), solve the salt/compound in the chosen solvent, close the lid and put a syringe though it. --> very slow evaporation. growing crystals in science is a bitch =)
8 years ago on Step 7
Are the crystals waterproof? Are they safe to touch?
Reply 8 years ago on Step 7
Well, I am sure they are safe to touch, and they GREW in water, so I'm sure they are water proof
Reply 8 years ago on Introduction
Sure and yes it's just a salt crystal.
Reply 8 years ago on Introduction
The crystal is safe, but it not waterproof. It will re-dissolve in water. Touching it will damage it. I think alum crystal has water of hydration as part of the crystal. If it sits in a dry atmosphere, it will slowly crumble to dust. If the atmosphere is too wet, the crystal will attract water and slowly melt away. It is best to display the crystal in a sealed chamber.
To color alum, you need to add chromium salts for purple. Other trivalent colored salts will give other colors.
Reply 8 years ago on Introduction
Thanks for your input, especially about coloring the crystals! Please keep in mind that the temperature of the water is a vital factor in whether or not the crystal will dissolve. In cold water, it is not affected much unless left for a prolonged period or movement is involved but for warm water your statement certainly holds true.
Since warm water is closer to gas form, the particles are moving at a faster rate and have more successful collisions with the salt particles making the salt dissolve faster.
On the other hand, cold water is closer to solid form and the particles move at a slower rate so collisions are not encouraged as much and therefore the salt will dissolve at a much slower rate.
As far as keeping the crystal in a dry atmosphere, it will take a VERY LONG time for it to wither away. Handling the crystal with care will help you avoid any breakage.
8 years ago on Introduction
I once did a demonstration with a group of kids from a local college; I got all the kids to grow their own alum crystals and they just loved it! I even synthesised the potassium alum from aluminium foil that the kids weighed out.
During this I had the idea of growing the crystal in a Thermos flask so the solution would cool very slowly, hopefully forming a nice crystal with large surfaces. Definitely something to try :)
Reply 8 years ago on Introduction
Hi, yep. Since the cooling period is a big factor, it is a good idea to use a Thermos flask. We noticed in a room with warmer temperature, the crystals formed differently.
8 years ago
Can you just use regular cooling salt?
Reply 8 years ago on Introduction
Try it and let us know!
Reply 8 years ago on Introduction
Tried. Salt is just pooling at the bottom
Reply 8 years ago on Introduction
Okay thanks. Well at least now you can just heat it up and gargle it when you have a sore throat now : )
Reply 8 years ago on Introduction
Tee! Hee! Good one ScienceKitStore 8)
Reply 8 years ago on Introduction
I'm glad you enjoyed my attempt at humor : - )
8 years ago on Introduction
This is really cool!
Using a rubber band is a brilliant idea, too. My kids would love this!
Reply 8 years ago on Introduction
Thanks, the rubber band idea was only a substitute for my missing string at the time but it worked out pretty well.
8 years ago
Are these crystals hard enough to use in jewelery?
Reply 8 years ago on Introduction
They are very fragile but like the member below mentioned, varnishing them would certainly help if you do it correctly.