The main reason new plaster requires a mist coat is it's absorbency. If the wall paper paste has already sized the wall it won't be as absorbent as fresh plaster. You probably have patches of wall unsized and some with paste residue on though, so as Vanneau recommends you should try a mist coat and see what kind of problems you have.
The main reason new plaster requires a mist coat is it's absorbency. If the wall paper paste has already sized the wall it won't be as absorbent as fresh plaster. You probably have patches of wall unsized and some with paste residue on though, so as Vanneau recommends you should try a mist coat and see what kind of problems you have.