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Stephen

repair chips in plaster hump molds

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I've got a few hump molds picked up a few nicks here and there while recently moving everything across the country. I poured them with pottery plaster. They aren't big issues but its annoying, not to mention time consuming to fix these issues when cleaning up the piece when leather hard. I have heard of some products but wanted to see if anyone had some go to ideas to keep these molds blemish free on an on-going basis?

I have some heavy duty wood glue I use for cutting boards I could try. It is water resistant.  Am I on the right track? 

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Stephen coming from a sculpture class background we were told piece have to be completely dry to stick things together.  I’ve helped fellow students. Very hard to be exact   

However...

... from my limited pottery experience I would say your Molds are a gonner.  Better to start from scratch.  

Could you shave/scrape the plaster down?

... writes the person who is doing a special summer project at school tomorrow- mold  making project just because of the nicks and scratches.  

Though I would love to hear if any folks have better idea. 

A reason why I have seen local artists make their drape molds out of wood.  They were drape though.  

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Whatever you use to repair the chips, needs to be absorbent, otherwise your clay will stick to it.  For big chips, you can add more plaster, just give the old a good few scratches first.  For smaller chips, probably not worth bothering, just keep on fettling the finished pots.

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Stephen I use to fix plaster sculptures,  I don't know it this will work for molds.  You clean the surface and on a mold I would put a few scratches in the break.  I would take a shallow plastic dish and put about one eighth of a cup of cool water in it.   Then I would sprinkle plaster in the water, probably a couple of tablespoons.  You don't stir it,  let it set for a few minutes and it is ready to use.  You take a tool that you can lift some plaster off the bottom and put it on your patch area.  Plastic tools work the best, remember no stirring You continue to do this until you have your hole fill,  you can sand it later when it is dry.  The line will be invisible where the old and new plaster meet and the new plaster will he hard  and not quite as absorbent as the old plaster.     Denice

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If you use Denice's method, you might make the defects a little larger by gouging them to make them deeper and wetting the area before you add the new plaster. Also keep in mind that the plaster patching material hardens chemically. It "sets-up" to harden and eventually will dry. You should also use the same plaster that your molds are made of. Give it a shot and if it doesn't work, make new molds.

JohnnyK

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Thanks everyone, great advice! 

Ya know I may have made it sound like more than it is. These are not chunks out but just really just a few very small nicks here and there. Some areas are also a small little irregularity like a little line or small indent from when I made them to start with. I just thought it would be nice to get them as perfect as possible so I don't have to do the same little cleanup every time I use them. When your trying to pop off 10 pieces and then get 10 more in place without spending too much time it's just another chunk of time per piece.

I sold off the masters with some excess stuff last year so when its time to actually replace some of these molds I have to buy the 3 masters again at a $150 cost and a bag or two of plaster and spend all day doing it so would like to put that off as long as possible.  

I think I will try the glue on one since I would have to buy a bag of pottery plaster for the patch and then use up the whole bag or toss. If the glue either causes sticking or falls out then I will progress to the patch try. Denise it is going to be really hard to keep myself from stirring it . B)

I will update this post after I've used them a few weeks and let you know how it went.

 

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The only reason I said you might have to scratch it was because it is a mold.  I never had to do that when I repaired sculptures,  they weren't going to get the abuse mold do.   Denice

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19 hours ago, Mark C. said:

One tip on molds -NEVER sell or get rid of the masters.No mater what you may think you will do with them.

 

I know, right. I'm pushing 60 and I just keep hitting my head on that same door jam over and over, also when I do any project and I am done with a tool for some reason I just always assume that I will never need it again so I just toss it to the side where ever I happen to be. I wouldn't say it sucks to be me but it is interesting.  

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I have a friend who made spice jars for stores-slip cast-they sold all in the 70's-he got tired of that and threw away his masters

20 years later was approched to make or sell the whole deal again-he had tossed the masters so had nothing .

I learned from him never to toss masters-that said I'm sitting on aroma therapy masters myself with zero plans of ever using them.

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@Stephen, my advice is to get that bag of pottery plaster, make one more clay casting in your flawed mold, clean that up as perfect as possible and recast it in your new plaster. Mending beforehand might give you more niggly little problems - up to you. Divots in the mold are much easier to deal with after casting than lumps.

Edited by Rae Reich

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