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Growing crystals has been a hobby for some time now. I got the idea from a book, the first book I bought myself as a boy of 10, 11 years old: 'Scheikunde thuis' ('Chemistry at home'). The funny thing is that I didn't try to grow crystals then in 1964. I made my first crystals in 2022.

I started with one of the easiest to grow: copper sulphate (CuSO4.5H2O), bought at Amazon.

sugar crystal copper sulphate crystal

My next experiment I did with normal household sugar (C12H22O11), which also worked out really fine.

Next I tried (potassium) alum (KAl(SO4)2·12H2O), which I bought as a deodorant in the supermarket. It didn't work out so good. I also tried kitchen salt (NaCl), without much success. Both I will try to do again soon. I have bought some epsom salt (MgSO4) in a local store and from Amazon I bought iron sulpate (FeSO4). I will try those too soon (probably spring 2024).

Where to get the substances?

copper sulphate from Amazon As a kid in the sixties I used to buy my chemicals at local pharmacies, but that's not possible anymore. So I use Amazon to get certain substances I cannot get in supermarkets, plant-growshops or from my own kitchen cupboards. I mailed several chemical companies that manufacture or supply chemicals, but they all seem to sell only in bulk quantities.

 

 

 

How to do it?

seed crystals growing copper sulphate It all starts with a (super)saturated solution of a substance in water. This you do by dissolving the substance into hot (not boiling) water untill no substance can be added anymore. Next let the solution cool and then pour a little bit of the solution out in a flat container, like a petri dish. Leave this a few days untill little cristals start forming. Choose the biggest and nicest formed cristal and wrap a piece of cotton thread around it. Not an easy job. Ok, then hang this thread with the seed crystal in a glass container with the saturated solution. The next days and weeks you will see the crystal grow bigger and bigger. It is important to keep the jar in a surrounding with a more or less constant temperature. Sudden changes in temperature affects the growth of the crystals in detrimental ways. This is what probably happened in my experiments with alum and kitchen salt that failed.

seed crystals

Some people use food coloring to give white or transparent crystals some color. I think that's a bit tacky.

I used this precise procedure for the copper sulphate crystal. On the same website are procedures for other substances too.

List of potential substances for crystal growing

Color Formula Substance AKA
white KAl(SO4)2·12H2O potassium aluminium sulphate potassium alum
purple KCr(SO4)2·12H2O potassium chromium sulphate chromium alum
white (NH4)Al(SO4)2·12H2O ammonium aluminium sulphate -
blue (NH4)Cu(SO4)2·12H2O ammonium copper sulphate -
green (NH4)2Fe(SO4)2.6H2O ammonium iron(II) sulphate mohr's salt
violet (NH4)Fe(SO4)2·12H2O ammonium iron(III) sulphate FAS, iron alum
blue CuSO4 copper sulphate -
pink MnSO4 manganese(II) sulphate -
green FeSO4 iron sulphate -
white MgSO4 magnesium sulphate epsom salt
orange K2Cr2O7 potassium dichromate -
purple KMnO4 potassium permanganate -
white KNaC4H4O6 potassium sodium tartrate rochelle salt
red K3[Fe(CN)6] potassium ferricyanide (NL: rood bloedloogzout)
yellow K4[Fe(CN)6]·3H2O potassium ferrocyanide (NL: geel bloedloogzout)
white (NH4)H2PO4 monoammonium phosfate MAP
white Na2CO3 sodium carbonate soda
white NaHCO3 sodium bicarbonate baking soda
white NaCl sodium chloride kitchen salt
white H3BO3 boric acid -
blue (CH3COO)2Cu copper acetate -
white C12H22O11 sucrose sugar
white C6H8O7 citric acid -