jgourlay
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blast from the past: olde skewl crystals?
One of the perks of fatherhood is that your kids want to hear stories about when you were small. This forces you to go a dredging, generally putting
your mind in that vein. A bauble last night triggered a long buried memory, I hoped you all could fill in the blanks.
Back in the 70's/80's you used to be able to buy these crystals growing sets as follows. 1. They came with some clear goo--I THINK it was labled
"silica gel". 2. Mix the goo with water in a gold fish bowl. 3. Drops in "rocks".
The rocks came in a little packet an there were white rocks and pink rocks and blue, red, green, and orange. The rocks look like someone took a
slurry, slathered it a quarter inch thick in a baking pan, dried it, then broke them apart with a hammer. Not natural rocks: chemicals processed to
look like little flat pebbles.
You'd drop in the "rocks" and after a few hours, little whiskers would start to grow off the rocks. After more hours/days, you'd have full blown
colored stalactites. These 'crystals' didn't have form like "hexagonal" or "cubic" nor were they dendritic like a tree: they looked like
stalactites. And they were very fragile. Shake the container, and they'd break apart.
However, they would get has high as the container was deep. I grew some 9" tall in a fish tank once.
Any idea the "ingredients"? I'd love to do this for the kids....
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ScienceSquirrel
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Here we are, scroll down towards the bottom of the page;
http://en.wikipedia.org/wiki/Sodium_silicate
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not_important
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Waterglass - sodium silicate - is the goo, the 'rocks' are soluble salts of transition metals that have coloured ions - iron, nickel, cobalt, copper,
manganese, chromium (as 'chrom alum' potassium chromium sulfate). Sometimes non-coloured salts were used too, magnesium and zinc. Usually the
sulfates, or mixed ammonium-metal sulfates, were used as they are not very hygroscopic.
The metal salt dissolves a bit in the water-sodium silicate mix. The silicate reacts with it, forming a membrane of the "metal silicate" in most cases
actually a mixture of silica and the metal hydroxide. Water permeates the membrane, dissolving more of the metal salts until the internal pressure
builds up enough that the membrane cracks, a blob of the solution inside spurts out and reacts on its surface to form more membrane to repeat the
cycle.
(PDF)
http://www.edu.pe.ca/agriculture/garden.pdf
http://www.bbc.co.uk/dna/h2g2/A4044845
http://chemistry.about.com/od/growingcrystals/a/aa060704a.ht...
(PDF)
http://www.rsc.org/ej/CP/1999/a905296h.pdf
It is not unlikely that in some countries attempting to put this together yourself will result in you being labeled a drug cook or terrorist, as well
as an environmental hazard, so proceed with caution.
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ScienceSquirrel
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Waterglass used to be available in old school pharmacies.
It was used for preserving eggs.
It is quite easy to grow good sized crystals of copper sulphate etc to use as 'seeds'.
[Edited on 21-7-2008 by ScienceSquirrel]
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ScienceSquirrel
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Sodium silicate aka water glass is widely available on eBay etc.
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StevenRS
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Hmm... I wonder what concentration, and what type of waterglass would work the best? I have tried this before with pottery grade sodium silicate and
distilled water, but it never seems to work right. I bet it requires a specific concentration of silicate to work.
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ScienceSquirrel
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I did this many years ago using the water glass available for preserving eggs and it worked well.
Have a look at some of the links above as some of them have quite detailed instructions.
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jgourlay
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Thanks! Min erals?
Thanks Guys! I'm going to surf on over to the links, now, so ignore the following question if that's answered in the links.
Anyone care to put together a list of the salts that would cover the colors of the rainbow? Especially purple, blue, and red? Preferably things that
aren't horrifically toxic--although I understand that none of these would be substitutable for lucky charms.
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jgourlay
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Thanks!
Gents, read the links all the info is there! Thank you!
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