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Tlouis 08-15-2006 12:08 PM

Repair broken plaster sculpture
Perhaps someone out there has had the same problem I describe below and can offer advice. After several months of hard work sculpting a slightly over life sized male torso--then hollowing it out to about 2" thick, it was accidently knocked off the modeling stand and crashed to the floor. There are a goodly number of large pieces (and hundreds of useless fragments) and I believe they could be put back together---but how best to do it? Would joining them with plaster alone be sufficient? Metal pins and plaster? A metal or wood armature required? Would epoxy be the best material? Once restoration is complete I want to make a flexible rubber mold and about 7 casts. Thanks for any and all suggestions.:D

Landseer 08-15-2006 12:22 PM

Re: Repair broken plaster sculpture
I'd use Elmer's white glue to glue the pieces.

BMBourgoyne 08-15-2006 02:19 PM

Re: Repair broken plaster sculpture
if the plaster is completely dry, white glue works well. Just coat each side of the crack with a thin coat and let dry (to seal the plaster), then re-coat and assemble. Masking tape should work to hold the pieces together.

if the plaster is still damp, white glue won't work. You could then use plaster to "glue" it back together, but this can be messy and difficult if you are trying to get a perfect fit (but better if you are filling gaps). Wet the plaster pieces thoroughly (but not dripping wet) before applying fresh plaster (otherwise the dry plaster will rob the new plaster of its water before it sets).

good luck

fritchie 08-15-2006 06:13 PM

Re: Repair broken plaster sculpture
I've never seen this problem, but have the following question. If you assemble large pieces using white glue such as Elmer's, and then wet the plaster to fill gaps and so on, will that weaken the glued areas enough for the piece to fall apart again?

Both methods sound OK to me, except for this problem. Maybe there would be enough internal locking for the pieces to remain attached. Also, if you have the piece thin enough in cross-section, you might consider plastering burlap on the inside as you reconstruct it, for bracing. I know this will add to weight, and of course, it also will have to be done with the original pieces damp.

terracotta 08-16-2006 03:00 AM

Re: Repair broken plaster sculpture

Maybe there would be enough internal locking for the pieces to remain attached. Also, if you have the piece thin enough in cross-section, you might consider plastering burlap on the inside as you reconstruct it, for bracing. I know this will add to weight, and of course, it also will have to be done with the original pieces damp.
This is my concern too. Thinking ahead, is the mould to be made with hot melt rubber or something which cures at room temperature, eg silicone or latex?

If hot melt (ie reusable) rubber is to be used, you will have to seal the surface with some kind of varnish to lock in the air bubbles, or soak the original in water - which would dissolve water soluble glues used in reconstructing it.

Presumably the piece was hollowed to save weight? If you want the reconstructed piece to have any strength, IMO you need some scrim or other fabric dipped in plaster on the inside for reinforcement, or even pieces of wood or wire mesh.

Landseer 08-16-2006 08:17 AM

Re: Repair broken plaster sculpture
Might want to read the instructions on any other glue than Elmers, rubber glue and contact cement are the only glues I know of that are applied on each piece, let DRY and then pressed together- every other glue I'm aware of - especially Elmer's and white glue- you simply apply a thin coat and clamp or weight over night.
I had a 600 POUND architectural concrete bust that was in a building fire and a section about 75# had cracked and broke when it was moved, I glued that back together with Elmer's white glue and it held perfectly fine for years. It only came apart when the entire sculpture was SOAKED for 2 days in a fire sprinkler flood I had by sitting in 6" of water, but when left in place and dried out the glue re-activated and hardened up again as before once the WATER dried out.

So unless you are planning to soak this thing in the bathtub, adding patching plaster or spackle is not going to affect the glue enough it will fall apart.
I have worked with plaster sculptures and broken mother mold shells in restoring/repairing and the plaster has to be SOAKED in water and totally wet, otherwise if you try adding more plaster on it or repairing it- the plaster just sucks the water out of the fresh plaster and it doesn't work well. You then have to keep damping the stuff down till the fresh hardens and then the two plasters usually have different hardness.
Use the Elmer's white glue, it's the easiest most simple fix

If all you are doing is pulling a mold off this thing, glue it and patch with spackle, bondo or plasticene, or plaster in small bits and damp the area you are working with a spray bottle of water and while the repair hardens- don't soak the thing in the bathtub in other words.

Tlouis 08-18-2006 10:28 AM

Re: Repair broken plaster sculpture
Hello Landseer, Brad Bourgoyne, fritchie, terracotta. Thanks a lot for generously taking time to offer advice on how to best repair my broken sculpture. Elmers seems to be the way to go, and my guess is it is innocuous enough not to compromise the curing of a brush on mold material from Polygel or Smooth-On. I'll keep you posted on results. Many thanks, Tlouis.
PS. If you care to, you can see some of my work at Click on Artists. then Desmarais.

Landseer 08-18-2006 12:36 PM

Re: Repair broken plaster sculpture
Elmer's is stronger than the material you are gluing- be it plaster, terra cotta or concrete- as long as you get a good clean break and you clamp/weight the pieces together nicely so there's no gaps- glue will not fill gaps and holes.

It will not affect the rubber, just don't apply so much it oozes out of the break and runs down all over the face, it doesn't take much to do the repair.

Here's a copy of the concrete bust I repaired per my previous post, it was 600# and 4' 1" high, hollow in the back with wall thickness about 2" or thereabouts;

While this is an extreme example of whta Elmers glue has held together, I used Elmers by the gallon back then to repair broken terra cotta architectural sculptures.
The whole side of the original - shoulder to the nose and down to the base was broken, you can see the left corner on the base where it had hit- the crack went up through there to the nose and then over to the top of the shoulder.

One test with Duco cement on something else was a failure- it lasted a week and the part I glued with it fell off.

zazie 05-10-2009 11:38 PM

Re: Repair broken plaster sculpture
I am trying to repair a patinated plaster sculpture for a friend but I am not sure what to use.

A supporting arm is broken in two places. The broken sections shows signs of past attempts at repair but the owner does not remember what was used. This means that the broken sections are not porous anymore.

I have had excellent results with a ceramic glue to repair fired clay but in this case I am not sure if I could use that glue or if Elmer glue would work better? Also, should I scratch the broken section to ensure better bonding?

Thanks for your help.

Mold Man Mike 05-12-2009 06:04 AM

Re: Repair broken plaster sculpture
I use Quick Stick from Polytek Development. It is a 2-part epoxy system. The bond is pretty strong and the epoxy is fast setting. This epoxy also bonds broken concrete.

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