Similarly, modern gypsum plasters have waterproofing agents added, which prevent them from breathing, and they are not as flexible as lime plaster.
Yn yr un modd, mae cyfryngau sy'n dal dŵr wedi'u hychwanegu at blastrau gypswm modern, sy'n eu hatal rhag anadlu, ac nid ydynt mor hyblyg â phlastr calch.