Adding cement to plaster Bonding Coat

[jim_in_sussex]

Adding some cement to Bonding Coat plaster gives an accelerated set.

Does anyone know:

What are the ideal proportions?

What effect does adding the cement have? - is there an adverse effect, make the coat more prone to crack, or what?

TIA

[Andrew Gabriel]

So does using an old bag of bonding coat. It's not like it takes a long time to set anyway.

On a plastering course, we added cement to finish coat to make it a one coat plaster for patching a small area. I've never actually done it in real life since then though. It was a relatively small amount of cement verses the amount of plaster, but no one was using accurate measures.

[Mike]

Don't know. But the cement based plaster I sometimes use in fireplaces specifically mentions to avoid any contact with gypsum plasters so presumably there's some incompatibility there.