What type of plaster should I choose for a block-carved plaster sculpture? I'm stuck with choosing the type of plaster for a sculpture I'm planning to carve out of a plaster block.

The names under which they sell  plaster tend to address their purpose in construction and don't really tell me much about their properties. The figures on the information sheet don't mean anything to me, either.

I think hard plaster would be best for the purpose as I would like to have some detail and have the sculpture stronger overall. So what I've found out is:


it is alpha plaster I should be looking for
they rarely mention anything about alpha or beta plaster on the package
they usually mix alpha and beta plasters in the market products
I should better look at the information sheet to find out about the strength, hardness, etc of the plaster


Could someone tell me what I should be looking for when choosing the plaster?

Eventually, if I have to choose between Plaster of Paris and construction gypsum would the second be a better choice for the purpose?
There are a variety of specialists which will stock a good range of plasters, these include sculpture and ceramics suppliers and well as those catering to industrial mould making. 

The plaster used for construction is not really what you want unless you find a supplier which caters for more traditional mouldings etc. 

A hard alpha plaster like CrystacalR  is very hard indeed and certainly takes some effort to carve and the various blends will give different hardnesses, setting times ect. 

I would look for a general purpose casting plaster as this should be somewhere in the middle of the range of hardness anything sold as dental plaster or plaster of paris should be fine. 

Ideally I would try to find a specialist supplier with a good range eg : http://www.specialplasters.co.uk/plasters.html

In all cases make sure you mix the plaster properly and with the correct quantity of water or you will get inconsistent hardness.