- Thread starter Jacksdad
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livias
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You 'should' use pure gypsum plaster ie plaster of paris because that is what the original cornice is made from. The problem is that it comes in 25kg bags and has a short shelf life so for such a small job I wouldn't bother and would use a fine filler such as Toupret (available from good decorating suppliers) instead. The procedure is ...
With judicious use of a scalpel and a water spray, remove subsequent layers of paint around the area because you want your repair to match up to the old plaster not to the paint. Don't use too much water or leave it wet for too long because gypsum plaster will eventually dissolve
Use your scalpel to undercut the back of the repair area so the repair will be wedge shaped and so trapped into its hole. Widen any cracks that you want to repair to 6-10mm so there will be enough body of repair material as thin smears of repair are useless. Roughen up the surface so new filler will stick well to old cornice. By this stage it will look worse than it did when you started but you will have a good base to work from
Add filler, building up in stages if necessary and finish off to the line of the original cornice with a small flat rigid bit of metal as the filler is going off. The pros use something called a joint rule which has a nice sharp edge but for a small job I expect that you could improvise
With judicious use of a scalpel and a water spray, remove subsequent layers of paint around the area because you want your repair to match up to the old plaster not to the paint. Don't use too much water or leave it wet for too long because gypsum plaster will eventually dissolve
Use your scalpel to undercut the back of the repair area so the repair will be wedge shaped and so trapped into its hole. Widen any cracks that you want to repair to 6-10mm so there will be enough body of repair material as thin smears of repair are useless. Roughen up the surface so new filler will stick well to old cornice. By this stage it will look worse than it did when you started but you will have a good base to work from
Add filler, building up in stages if necessary and finish off to the line of the original cornice with a small flat rigid bit of metal as the filler is going off. The pros use something called a joint rule which has a nice sharp edge but for a small job I expect that you could improvise
88v8
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Not too difficult.
Recently discussed here
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14281
For small chunks as you illustrate, Polyfilla would do the job, or plaster of Paris.
Ivor
Recently discussed here
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14281
For small chunks as you illustrate, Polyfilla would do the job, or plaster of Paris.
Ivor
Nigel Watts
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I wouldn't use pollyfilla. It's far too sticky to get a good finish with a rule. Plaster of Paris on its own does not have enough body when wet, but mixed with some lime putty it's pretty good, so long as the background is well wetted first and the mix is well pressed in as it sets (otherwise it shrinks too much). Lime putty unfortunately can't easily be obtained in small quantities.
Keithj
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I get lime filler in 1 kilogram pots for notalot from Anglia lime. I think it's a 50/50 mixture of lime putty and chalk.
I would be tempted, if the need arose, to try repairing mouldings with it. I'm sure it would do a better job than polyfilla, but it would need to be kept covered and moist for a few days to let the surface carbonate.
I would be tempted, if the need arose, to try repairing mouldings with it. I'm sure it would do a better job than polyfilla, but it would need to be kept covered and moist for a few days to let the surface carbonate.
Feltwell
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I appreciate that a plaster of paris / lime mix or lime filler would be best if you're repairing a large section and using a rule to get a good finish, but for what look like the very small sections that Jacksdad has to repair, surely careful use of a "normal" powder filler followed by careful rubbing back when dry would be good enough? A crack in a section I'd undercut into a V shape then press filler into normally, and sand back smooth very carefully once dry.