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Preparing old victorian plaster coving

hi all
I’m diy decorating a large hall atm + thus far have used water based products only & really appreciated the difference

my coving has an irregular surface- overpainted with dead flat oil - but showing large areas where previous paint coats have partially flaked away [painted over with the dead flat oil & looking fairly grotty]

previously in other areas I’ve used alkali resistant primer /painstaking pollyfilla + sanding followed by more ARP then dead flat top coat x 2-3

sticking with the water based theme I’d like to try ?bullseye123/?ESP ,then gesso,sanding then more undercoat followed by finish coats

what wld everyones advice be?
how do I vacuum sand this kind of surface?
many thanks in anticipation

also -wld it be better to sand out these roller marks -made by dead flat oil - or re line with paper {shown in the same photo}


cornices really can throw a few challenges our way! After removing flaky stuff and sand back gently - plaster work is very soft - I use the Festool hand sander*** with Mirka foam interface to get around the curves using 120/180g - then Henry it clean with a round brush attachment.
Depending on surface I’ll sometimes use Zinsser Peel Stop and then apply Toupret TX110 filler using a fairly wet mix applied by brush ( a technique I learned form a cornice installer) then if possible, flatted off by blade.

I’m with you all the way on water based systems but cornices are where I’ll often use solvent based Zinsser AllCoat. Because I have found frequently that water based products (emulsion) can draw out old water stains. I don’t rate 123 as a stain blocker so All Coat does it for me, and its done in two coats with a great, flat, white finish.

If its a straight line cornice as in pic, apply by brush. For moulded and decorative cornices (acanthus leaves, roses, egg and dart, grapes etc) I spray.

All that said, cornices can throw up a range of challenges that need dealing with on an individual basis

***FESTOOL ACCESSORY 496962 HSK-A 80x130 Sanding block


thanks Dave
thats v clear + specific advice-just what I need!
I’ll give that a go

That was an ace reply from Dave there. A layer of peel stop would probably be a good idea all round. If it is thinned it should penetrate any soft bare plaster and harden it up well.

The only area I would differ from Dave is that I wouldn’t be worried about old stains. I have had exactly what he said, and as with him have found the 123 annoying to use as a stain blocker (not really usable unless you have nice and dry conditions.) But I would just treat the stains with a solvent based blocker if they appear.

I would just be using an acrylic primer on top of the peel stop and paint with any coating you want on top of that.

Back in the day, ornate cornice would be done in soft distemper, so the main issue was deciding how many toothbrushes and buckets of water did you need to clean it back for another cycle.

Modern paint solutions are quite involved in comparison and not always labour saving.

This article from Patrick Baty is a good resource

Soft distemper is applied by brush and can be removed with a wet sponge when dirty or in need of recoating. Its great advantage is that when applied to ornate plaster ceilings, for example, the detail is not lost as it must be removed before redecoration. An emulsion paint, on the other hand, would add yet another disfiguring layer that will eventually require removal.

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Sand them out and apply the paint again. All that lining work will give you another flat surface and still you will have to avoid roller marks. (SO nice to hear mention of Alkali resisting Primer, a super product in its place)

Hi dave why use zinerser peel stop on coving any paticulur reason?

hi tpdog i do quite a bit of cornice restoration and have found alec taranti to be invaluable for small filing tools for those tricky bits. its also worth while making a scribe from zinc plate to both use as a scarper and a scribe when it comes to filling . there are also different shaped surforms available from the auto industry that are good for convex and concave surfaces like your Edwardian cornice the prep is key on a cornice as the lines need to be clean to make it pop