The size of the seed crystal shouldnt matter too much. The key should be very slow formation (control the rate at which water evaporates to slow it) and ensuring the container you use has no nucleation sites other than the starter crystal.
Of course you also need to make sure your seed crystal is itself a perfect single crystal and not multiple crystals.
Rock salt, is usually very far from pure, particularly the kind used for melting ice. You need pretty pure salt to create nice crystals. That said if the rock salt were pure it would work as good as any. Once its dissolved in the water salt is salt if its pure. The seed crystal wont matter so much if its from rock salt or small granualted salt if its a single crystal.
@freemo @zleap @piggo
Either way, it reminds me of this
https://www.amazon.com/National-Geographic-Mega-Crystal-Growing/dp/B01C3DSKTY/ref=asc_df_B01C3DSKTY/?tag=hyprod-20&linkCode=df0&hvadid=242166129524&hvpos=&hvnetw=g&hvrand=6829070533420193425&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9032467&hvtargid=pla-505056962157&psc=1
Yeah i had one with Copper Sulfate, Cobalt Chloride and Water Gel (sodium silicate) which when you drop a crystal in, it grows upwards like a plant does.
When you have a collection of chemicals they may or may not form crystals. More often than not though non-pure chemicals form smaller crystals, if they form crystals at all.
You can grow Alum (Aluminium Sulfate) crystals on rocks. By pouring the solution over and then waiting.
I want to have a go at some of this.
Soon after I bought mine, some of the chemicals were banned or the kits were banned with those chemicals in (can't remember ), as a child accidentally drank some.
A very good reason not to let kids do this stuff in the bedroom as normal drinks look similar.
Was not me doing that, another child, who may have died or become very ill as a result.
Yeah, You can still get chem sets but the chemicals in are safer i think.
Kids should be supervised either way. esp with Methylated spirit burners.;
@freemo @piggo
I am using an old Conical flask at the moment, I take it rock salt won't work then.