Grow your own Purple Crystals [SLYT 4 min 4 sec]
July 24, 2017 7:53 AM   Subscribe

Growing your own purple crystals. A fun, simple and educational diy project With a little potassium, some aluminium sulphate, water, a glass container, an airing cupboard (or similar space), and a little patience you can cultivate your own decorative purple crystals. This video explains how.

Video Transcript for those unable or who don’t want to watch video:

"Hello everyone, in this video I'll show you how to grow a beautiful purple single crystal.
For this we’ll need the following substances – potassium and chrome alum. To begin, let’s make a mixture of alum.
To do this, take a glass and weight 100 gram of aluminium potassium sulphate and 12 grams of chromium potassium sulphate in it. Adding chrome alum will make the crystals violet.
Then, pour 400 ml of a very hot water into the glass and stir until all the alum is dissolved.
After it’s all dissolved, leave this glass for a few days to let the crystals form at the bottom. A day later pour the alum solution into another container.
As you can see a lot of beautiful little fused together crystals were formed at the bottom of the glass. Now pick open the mass of the crystals and put them in a bowl.
Choose from this mass the most beautiful and large crystal. This crystal will serve as a seed from which a large crystal will be grown in the future.
The solution, which previously was merged can be now filtered but that is optional. Now tie the seed on a thin fishing line and hung it in a solution of alum on a pencil or a stick.
Now we can only wait for the crystal to grow. Over time, water will evaporate from the solution and excess alum will form the crystal that is hanging onto the fishing line.
After some time the crystal will begin to take a regular geometric shape that is defined by the crystal lattice of a substance.
For alum it is octagonal or octahedron. Also, during the crystal growth excess crystals will grow as well on the bottom and the line of the glass, and they should be removed.
Though it’s better to save these crystals as it is possible to prepare a solution and raise other crystals out of them in the future.
Also, in single crystals growing it is important to avoid extremes of temperature and pollution of the solution.
After 2 months my crystal become large enough and I decided that I can stop its growth. I pulled out the crystal from the solution and desiccated its surface with a napkin.
Next I covered the crystal with colourless nail polish, one or two layers is usually enough. It is important to protect the crystal from further destruction.
After the nail polish has been dried out it’s okay to take the crystals with bare hands. Crystal growing is very exciting activity that develops patience and mind.
I raised two purple crystals. One is dark and the other one is more transparent and bright. Now, ladies and gentlemen, as we have done a long journey growing these crystals let's just enjoy their beautifulness without any further comments.”

posted by Faintdreams (8 comments total) 34 users marked this as a favorite
MetaFilter: let's just enjoy their beautifulness without any further comments.
posted by Rock Steady at 8:56 AM on July 24, 2017 [15 favorites]

weigh 100 gram of aluminium potassium sulphate and 12 grams of chromium potassium sulphate in it.

As a teen, I got really into growing super large sugar crystals but really wanted to try my hand at making fancier and more colorful ones. I got a book on the subject with plenty of colorful photos. Instructions like these, to weigh things with gram precision, pretty much made that impossible as good scales (triple beam balances, at the time) required for that weren't affordable, least ways to me. Today cheap electronic scales are practically standard in most home kitchens. Perhaps I'll give it a try now, as a crusty old adult.
posted by Insert Clever Name Here at 9:35 AM on July 24, 2017 [1 favorite]

If you like this, you'll love crystal gardens
posted by lalochezia at 10:30 AM on July 24, 2017 [4 favorites]

Although I love the idea of growing crystals, my time in the lab was usually spent trying to make sure something didn't crash out of solution, so intentional crystal growing is a little nerve wracking. I hold that irrational fear to this day even when I make simple syrup for cocktails. But then I drink a cocktail and get over it quickly.

Maybe I should face this thing head-on and rig up something to make an industrial sized crystal. It seems to require spinning.
posted by Muddler at 3:16 PM on July 24, 2017 [5 favorites]

MetaFilter: It seems to require spinning.

And holy cow that's a big crystal. I knew the NIF was growing some of the largest crystals in the world but I didn't realize it wasn't a hot process. I'd always assumed it was extremely high temperature process like growing silicon or quartz ingots with molten solid materials, not what looks like a low temp high saturation solution crystal process.
posted by loquacious at 5:14 PM on July 24, 2017 [1 favorite]

I developed a healthy amount of caution about Chromium after taking a welding class... the stuff will kill you quite happily... be careful.
posted by MikeWarot at 6:56 PM on July 24, 2017

I developed a healthy amount of caution about Chromium after taking a welding class... the stuff will kill you quite happily... be careful.

As long as you don't drink the solution, or try to smelt the chromium back out of the crystal you should be fine. It is used in stainless steel production, which is probably what your cutlery is made from. The leaching of chromium from the cutlery would be microscopic if any, but it is still a minor yet essential nutrient, just bad in large doses and at the higher oxidation states.
posted by koolkat at 5:56 AM on July 25, 2017

precision, pretty much made that impossible

Today's quandry is the purity of the said reagents. Something that says 98% on the label (there are really diminishing returns on purity vs efficiency) may only be 63% or something, if obtained from an untrusted vendor.

YMMV depending on whether you have the same grade reagent as the demonstrator on YT (or wherever, especially "legit" demo labs), or what you expect when setting up a reaction.

Also, double check whether the reagent required/offered is anhydrous or hydrated; this will affect its molecular weight and you might not be using the optimal percentages/weights.

Thermometers are another source of error; the relative difficulty of controlled cooling for optimum crystal growth is another difficulty factor. Depending on ambient and the cooling curve, a DIY sous vide setup could help a lot. If the thermometer's off, you might not get the same results.

Don't be discouraged! If you're not getting optimum crystal growth, control what you can and then try to determine the purity of your primary reagent(s), either empirically (trial and error testing, essentially, but you need to have high confidence in your other reagents) or analytically (use some method of determining purity; at large scales, its worth outsourcing to an accredited 3rd party analytical chemistry outfit and use fancy equipment - but modern Chemistry started pretty much by Lavoisier's "Traité élémentaire de chimie (Elementary Treatise on Chemistry)" in 1789).
posted by porpoise at 9:42 PM on July 25, 2017

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