Powdered clay bodies are often used as a base for making up casting slips. The recipe we generally recommend for making up a casting slip from powdered clay is:-
25kg powdered clay -- 35-87.5g* sodium silicate 120tw -- 30g soda ash -- 10lt water
*sodium silicate (deflocculant) addition will need to be adjusted accordingly to achieve correct fluidity. Too much deflocculant can have the reverse effect on a casting slip, causing it to thicken, so it is best to add it gradually, mixing all the while. Fine-tuning the fluidity is best achieved with sodium dispex.
If you can find a copy (it is currently out of print), we would highly recommend the book Ceramic Faults & Their Remedies which gives lots of useful information on slipcasting and the issues you may come up against.
Our Powdered Clays can also be used for making "seed bombs": Flower seeds are mixed with compost, clay powder and a little water to form balls. The balls are then thrown onto patches of bare ground where the seeds can germinate.
See our Technical Information Sheet "Safe Handling of Powdered Ceramic Materials"