Repairing plaster cornice!??? PLEASE HELP!?

[drummer_boy]

hi, how do i repair my ornate cornice & other plaster mouldings? i have saved most of the sections which fell down and i was wondering how to join them back together? i also have some straight runs of cornice to repair......how do i make a mould &/or how do i make a template? on the said cornice there are corner blocks, can i use some sort of modelling clay to take an imprint of these? is that the easiest way to tackle those bits? (the sections for repair are very small most are just a few inches long although 1 is around 12" long).

Also, what is the best way to fix plaster cornice to the walls & ceilings? & do i fill in any gaps with plaster, wipe away the excess & finally sand down when dry?

thanks in advance for your help, i am so suprised at the number of so called specialists who have told to just rip it down & replace it with a 'standard' victorian reproduction!!! what the hell has happened to trying to save & restore this most beautiful craft? have we learnt nothing from our forefathers!?

Yours, Chris Parker

 

[Nigel Watts]

Traditional plaster cornices were generally "run in situ". Temporary wooden battens were fixed the the wall just beloe the cornice to provide a rail along which to run a box-like structure containing a reverse profile of the corince filed up in a zinc sheet. Wet plaster (usually a 50:50 mix of lime putty and Plaster of Paris) was applied and the contraption run back and forth. The process is repeated a few times until the cornice has been formed.

Corners, of course, cant be done in this way. When the straight sections had been completed, the inside and outside corners would be made by hand, using a steel rule resting on the completed sections.

Moulded decoration was sometmes added after the straight sections had been made. This would often be made in short, precast units and fixed in place using the same lime putty/plaster of paris mix.

The vast majority of firms specialising in plaster cornicing these days wont be interested in doing in situ work - they much prefer to make lengths in their workshop and simply glue it up on site. This apprach is not suitable for older buildings.

Decorative sections can quite easily be copied by making silicone rubber moulds and casting new ones in pure plaster of paris. Short lengths of straight mouldings, and corners, can be reapired using the rule technique. Longer sections may require running using the in-situ method described above.

I have done a good deal of cornice repairing of the kind I have desribed. I had no experience or training, but was able to pick it up fairly easily.

Good luck!

Nigel

 

[drummer_boy]

Hi & thank you for a speedy reply!

Could the corner molds be done using modelling clay as it seems like the easier option for a novice like myself? You mentioned using silicone to make a mold, what type of silicone & what would by the step by step process for doing that?

Thanks in advance, it's fantastic to have sooo many people out there who are willing to take the time to offer the help!

Chris.

 

[plumbers mate]

This blooming forum - try to alter something and the whole mail vanishes - great.

I'll try to remember what I've just written......

To make a simple mould, go to a model shop - eg railway modelling where they will have several types of kits/materials to choose from.
I got some to make "rocks" for a layout this way as do most modellers.

**I have NEVER tried this on a piece of cornice or ceiling rose** I have been tempted to but the cornice is getting on for 9ft above the floor so I've chickened out so far!

The theory would be to get the stuff - whose name I will get from home tonight - which consists of two materials which you mix.
This looks like Copydex - thick and white. Paint a nice layer over the plaster and let it dry - it will be clear when dry.
Repeat the process till you have a fairly thick total layer and let it get really dry. Then carefully peel it off and you should have a good mould.

Make sure the mould is level or you'll get a sloping back on the finished piece of plaster, tap it a bit to get rid of all the bubbles, let it dry and voila! a piece of cornice.

I need to get little decorative leaves replaced on mine and don't know if this would work with a larger piece.

If this version vanishes - tough!

 

[drummer_boy]

Hi there! thanks for your advice i'll certainly be trying these ideas to see which one works best!..................can anybody tell me how to fuse/re-join the broken peaces of trim? they where and i guess still are, the edges of a beautiful dome/skylight in our hallway........i think i read somewhere that you have to soak the ends in water for about 30 minutes before rejoining them? but what is the best material to use to stick them back together with.................plaster of paris? lime? or something else!!!?

Anyone know?

Thanks, Chris.

P.s. this forum is great! you people are very kind to offer your knowledge & ideas!!!!

 

[Nemesis]

If you do want a specialist, there are some around who can repair. SPAB will have names to try. However, if you feel you can tackle this, have a go!

 

[Nigel Watts]

A good sculptor's supplier should be able to advise on mould making and casting technique. Tiranti's in Warren Street, near Euston Station is good. They stock all the materials and the books on how to do it.

I stick broken bits of plaster ornanment back together with UHU. I reattach ornament to the ceiling with a mixture of Lime putty and Herculite (a strong type of Plaster of Paris).

 

[thiambal]

Spotted this company in a magazine - apparently one of the few companies left using traditional techniques and they will make new paster to match exitsing patterns

http://www.butcherplasterworks.com/

 

[plumbers mate]

Ah, I promised to send the name of the moulding stuff that I use for making rock moulds -

It's called Mouldmaker by ArtCrafts -- it's basically a latex material so don't get carried away with it or perhaps ....
;-)