Growing Crystals: Recipes

Growing Crystals: recipes
you can try, but first a few points...

Something's not working?

Check your crystal everyday to see if it is growing. If it isn't, you probably haven't got a saturated solution and your seed is simply dissolving. Take out the seed crystal, reheat the solution, add more chemical and try again.

Or your temperature might not be constant enough or your jar clean enough. If you don't find seed crystals growing on your saucer, try hanging a piece of thread in the jar. Small crystals should grow on the thread which you can then separate. Read the recipe for Alum Crystals and you should understand this section better.

Saturated Solutions

When you add a spoonful of sugar to a cup of tea or coffee, you usually stir it to help it dissolve. There are two ways of helping something dissolve in a solution: stirring it and heating it up. But even if you do both of these, there is still a limit to the amount of sugar you can add to your drink. Eventually you'll reach a stage where no more sugar will dissolve no matter what you do: your drink is now saturated.

When you grow crystals, you need a saturated solution or the seed crystal will just dissolve the moment you add it to the solution in the jar. Rather than growing crystals, you'll be dissolving them. Read the recipe for Alum Crystals and you should understand this paragraph better.

Seed Crystals

Seed crystals are formed as the water in the saucer evaporates. The tiny particles of chemical in the solution gradually join together. The crystal in the jar also keeps growing as the water evaporates. As the solution gets stronger, the particles crystallise around the seed crystal.

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Growing Crystals: recipes

Alum Crystals

Here's how to grow crystals from Alum, but the method is the same whatever you want to grow crystals from.

You can buy alum powder from a chemist's shop and growing the crystal will take about 3 weeks. Pour 600ml (1 pint) of water into a saucepan. Add 100g (4oz) of alum powder. Gently heat the mixture and stir it to dissolve the powder. Then add as much alum powder as you can until no more will dissolve.

Let the mixture cool, then pour some into a saucer and stand it somewhere cool. Pour the rest of the solution into a glass jar. Stir an extra tablespoon of alum into the jar to make a saturated solution. Cover the jar with a cloth. After a few days, small crystals should start to grow in the saucer. Leave them until all the solution has evaporated then choose the biggest as your seed.

Carefully tie a long thread around the seed crystal and wind the other end around a pencil. Hang the crystal in the solution by balancing the pencil across the jar. Put the jar somewhere warm like the airing cupboard. The crystal should grow for about two weeks. When it stops growing, take it out of the jar and wrap it in a piece of tissue.

Once you've grown more crystals of different sizes and colours use something other than alum you can arrange them in a display.

Potassium Ferricyanide

Also known as "Red Prussiate of Potash" and has the chemical formula of K₃ Fe(CN)₆. This recipe gives red monoclinic crystals.

Dissolve 93 grams of potassium ferricyanide in 200ml of warm water, cover the solution, and allow it to cool. Do not be especially afraid of the word "cyanide" in the name; this substance is no more poisonous (and no less!) than the others in the list.

Copper Acetate Monohydrate

Chemical formula: Cu(CH₃COO)₂.H₂O. This recipe gives blue-green monoclinic crystals.

Dissolve 20 grams of copper acetate monohydrate in 200ml of hot water. If a scum of undissolved material persists, add a few drops of acetic acid and stir well. Cover this solution, and allow it to cool and stand for a few days; usually it will deposit crystals spontaneously.

Calcium Copper Acetate Hexahydrate

Chemical Formula: CaCu(CH₃COO)₂.6H₂O. This recipe gives blue, tetragonal crystals.

Add 22.5 grams of powdered calcium oxide to 200ml of water, pour into the mixture 48 grams of glacial acetic acid, and stir until the solution is clear. If there is a small insoluble residue, filter the solution. Dissolve separately 20 grams of copper acetate monohydrate in 150ml of hot water. Mix the two solutions, cover the mixture, allow it to cool for a day. If it does not deposit crystals spontaneously, let a drop of the solution evaporate and scrape the resulting seeds into the bulk of the solution.