British Gypsum Thistle Hardwall is a gypsum undercoat plaster for use on aircrete blocks, common bricks, medium-density blocks, dense blocks and metal lathing. The combination has superior impact resistance, early surface drying, a higher than normal resistance to efflorescence, and gives a durable base for the application of decorative finishes. Thistle Hardwall is a lightweight, safe and easy to use product, requiring only the addition of clean water to prepare it for use. It is suitable for application by hand or by plaster projection machine. If you would like more advice or assistance on this or any more of our products please contact a member of our team today. PLEASE NOTE :- Returns Policy on plaster products: Due to the volatily of plaster products, once delivered or collected we regret that we are UNABLE to accept materials back for credit. .