Caring for old plaster

[leucothea]

No doubt the answer to this question is buried in the archives but what would be best practice here?

I have this kind of plaster everywhere (presumably original 1741) under modern lining paper and would like to repair and finish it properly.

It undulates nicely. There are some cracks and a few weak/flakey bits.

What would people recommend?

 

[leucothea]

Could I remove the loose material and ‘smooth it over’ with a very thin layer of e.g. lime green solo? And then lime wash/distemper?

 

[Kearn]

No need to add lime, especially ones with chemiCals added in.

You won’t get a genuine top coat to adhere, without some key but likely there’s no need anyway by the looks of it? Trying to scratch a top coat is near impossible as it’ll fail being so thin and vulnerable.

Some would recommend a primer like DG27. But I wouldn’t waste the money for a chemical adhesive which inhibits performance of the lime.

Personally, if you’re line washing, just brush down what you have to remove anything loose and detached. Patch any hole with polyfilla/top coat if big enough. Then limewash to pull it all together.

 

[leucothea]

Thanks.

I had thought about doing that. It also seems to be smoothable by sanding to some extent.

My only concern was with the 'edges' of previous lime wash coatings making the final lime-wash finish look a bit untidy. I will do some experiments.

 

[paulc]

Could I remove the loose material and ‘smooth it over’ with a very thin layer of e.g. lime green solo? And then lime wash/distemper?

Distemper is just water, finely ground chalk, and an organic binder (usually rabbit skin glue). Once on a wall, subsequent coatings of anything other than more distemper can just peel off. Lime wash is the way to go. If you want a bit of body to it, add some ground chalk (whiting). As it dries, the lime wash can be burnished with a stainless steel trowel to give it a slight sheen.