How do I make a SAFE calcium block for birds?

I heard not to use Plaster of Paris since it’s not safe. I do need an ingredient that will harden up in the molds I have made.
I heard Human Grade Calcium Carbonate powder is fine but will that harden up when mixed with water? And where would I find it in large quantity bags?
I heard not to use Plaster of Paris since it’s not safe. I do need an ingredient that will harden up in the molds I have made.
I heard Human Grade Calcium Carbonate powder is fine but will that harden up when mixed with water? And where would I find it in large quantity bags?

Human grade calcium carbonate will harden up but is softer in the finished product then plaster of paris. Its a safer and better option the calcium carbonate but the reason plaster of paris is used more often is due to the fact it hardens well and stays together better for sales and production.
Calcium carbonate is used in my occupation which is leadlight and stained glass work. We use a product called whiting which is actually calcium carbonate and it is used in the puttying process of leadlighting. Inquiries I made have confirmed it is food grade calcium carbonate but as yet I havent tried making calcium blocks with it.
For you to make your shaped calcium blocks and them be hard enough for handling and maybe packaging you may have to resort to the plaster of paris. All the commercial ones use plaster of paris.
BUT I understand your reluctance to do so, as reading up on plaster of paris it is quite harmful. So a message to all those using commercial calcium or mineral blocks out there………read up on plaster of paris and then rethink giving this to your birds.

IT BROKE!