Tuesday, 22 December 2009

Latest experiments!

Dear Reader,

I never get tired of growing my own crystals. Many of you will have grown crystal gardens in your childhood days, perhaps from salt or copper sulphate. You can buy kits, of course, to help with this, but a lot of them cheat by making chemical reactions happen in front of your eyes. Those ones really don't tell us much about natural minerals...

No, the best methods are those that let the crystals grow naturally, as they want to. We merely... encourage them. Perhaps with an oven, if we need to. Actually, I must confess to getting bored as well, so I'll speed them up when I can. I don't think it makes much difference to the result, though - it all comes out in the wash (unless you're using potassium cyanoferrate - that stains like anything!).

I should probably explain how to do it, too. Take lots of whatever you want to grow, dissolve it in water, and let it evaporate. That's about it, really.

So, guess what? I've got hold of some boric acid, copper sulphate, and aluminium sulphate. They're all nice crystals, if a little toxic. I make very sure not to get them mixed up with my muesli, I can tell you. As long as you don't eat/drink/inhale/spill them, they're pretty harmless. Copper sulphate gives you a gorgeous blue colour when you dissolve it in water, too. Here's some I've started to make at home.

Now, I read somewhere recently that if you dissolve copper sulphate and salt (sodium chloride)together, you get a really nasty liquid that's used to etch metal. I've not heard what crystals you get when it evaporates, though. Of course, it's far too dangerous to do this at the museum - they wouldn't like that at all. So I've done it in my kitchen instead. :)

For some reason it turns a wonderful dark green colour. That's always a bad sign - I mean, would you drink something that looks like that? Then, of course, I had to test the alleged metal-etching powers of the mixture... does it live up to expectations..?

Here's what happens when you dunk a bit of scrunched-up aluminium foil in it. Note the fizzing. I'm not sure what gas was coming off, but it was probably chlorine or hydrogen, so I'm not going to get too close...

On the right is the aluminium after 20 seconds of dunking. Good, eh? Any guesses as to which crystals will end up growing in that horrible gloop first? Sodium sulphate? Copper chloride? Just some weird green gloopy stuff?

You'll just have to come back and find out. I honestly haven't the faintest idea. But when I do know, I'll tell you. Along with revealing what's in those other beakers...


  1. Dear Dr Rock, Love your Crystal garden experiment - check out Richard Hiorns Turner Prize crystal garden on www.tate.org.uk

  2. Good evening, Mark, and thanks for providing the first comment. So there really is someone using this strange technology!

    Thanks for the pointer - a rather pretty, if over-the-top statement of grandeur, in my opinion. He may have used a *lot* of copper sulphate, but where's the imagination? Why didn't he put some metal fittings in, or if he did, what happened to them? As a scientist, Mr. Hiorns is clearly a bit of an amateur. Even if it is rather impressive... actually, I wonder... but no, no, I'm sure they wouldn't let me...

  3. Dear Doc Rock,

    Where would you find 11 meter crystals in a cave? (A clue and its not Rock(et) science - somewhere in Mexico).

  4. Ah, that's be the famous Naica Cave in Chihuahua (27°50'N , 105°29'W). Yes, I did have to look up the last bit, by the way. :o)

    The crystals (of gypsum) are amazing, and their huge size seems to be down to the precise conditions of growth being maintained for a very long time. I must say, I wouldn't personally find them, though - it's 60 degrees, toxic, and 100% humidity down there!

    There are some papers to read for the detail on these here if anyone's interested:

  5. Your fame is spreading! Check out www.exhibitfiles.org

    What's up doc? Still trying to find out how many pet rocks you have in your store - I counted 52 before my wife told me I looked stoned.