Dental Alginate from 'dougarts' Modelling Magic on Ebay.
450g - £3.99 postage £1.99 - By volume produces enough for 5 or 6 Hirst moulds.
This stuff is pretty weird. The faint of heart should keep well clear. Those with sensitive sensibilities better not read the instructions - can also be used for moulding 'private parts'.
With all that said you may wonder what the heck this stuff is getting mentioned on a Hirst arts forum for.
Simple, if you are carving a master and want to get a rough copy, to play with, quickly and easily this is what you use.
The instructions say a mix of100g powder to 220cc water. Having tried that ratio and screamed to herself to slap in some more water on the first batch we discovered that just under 1:1 by volume worked a lot better.
The instructions also state that it turns purple when you add water then pink as a warning colour to say it needs pouring then white when set. In use it stays purple then after a while turns pink then immediately white. Don't wait for the pink state before pouring. If this does take the 3 minutes they claim to set, it's the shortest 3 minutes of my life
The mould is not durable and a bit like a wet jelly on steroids. Never try to cast without the supporting Lego.
The resulting cast is a bit rough wi