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Caped Crusader

Registered: 02-2004
Location: london
Posts: 1262
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Parting Agents


I was wondering if anyone can help…

My cowl sculpt is all but done, but when I did my leg armour sculpt I had real trouble with the mold.

The sculpt was clay - coated with waterproof plastic masonry sealant. I was using a plaster/polymer (reinforced with fibreglass) for the mold but the water-soluble parting agent I used was less than great. It beaded over the sculpts surface and getting them apart afterwards was a nightmare.

Any old pros have any advice on parting agents that they care to share?


Last edited by Deadly Lemur, 3/18/2006, 10:09 pm
3/7/2004, 7:08 am Link to this post Send Email to GoldenAge   Send PM to GoldenAge
 
Brin Londo Profile
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Keeper of the Cave


Registered: 02-2004
Location: Mississippi
Posts: 9351
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Re: Parting agents - help !?!


Usually if it's a clay sculpt, you don't have to use a release agent. Are you using something like Ultra-cal 30 for your mold?
I'm not sure what the plaster/polymer mold making material is.

---
You don't choose the Bat, the Bat chooses you.
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cursedbat Profile
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Apprentice

Registered: 02-2004
Posts: 297
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Re: Parting agents - help !?!


There is allot of things you can use as a release but Like Brin said I'm not quite sure about your materials.
Usually a little crystal clear is used for a sealer followed by the matte to get the splash coat to stick but depending on the make up of the finish spray you used you can get different results. Spray paint will bond to plaster big time for example.
You can use vasoline thinned down or potters soap but the technique for laying down your splash coat can can change with some releases.

---
Dont disrespect the archetype with the pathetic sides of the human condition


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Caped Crusader

Registered: 02-2004
Location: london
Posts: 1262
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Re: Parting agents - help !?!


Thanks guys -

I starting to get a feeling that the way i'm going about things is sufficiently different that I might just have to keep on with that old standby "trial and error"

I realise that generally speaking the mold is the finished article cast in a tough material, but with me it's the other way around.

For the record, My sculpt is a reinforced plaster lifecast with a cowl shape in Newclay (mixed with a hardening agent) and then coated in a plaster-polymer* mix which I can then finish sculpting with tools.

I know that sounds a bit excessive but it's what i know - and it needs to be super hard when finished otherwise it will crack when i start hammering it to make the cowl.

I wanted to take a (2 or 3 part) mold of it in case i fluff it up - at least that way i can make a copy.

I may just cover it in saran wrap and dip it in a bucket of concrete. Ah well....

*Brin - plaster polymer is just base alpha plaster mixed with a liqid polymer instead of water, gives it a tough plastic like texture and makes it very hard.
3/7/2004, 9:41 am Link to this post Send Email to GoldenAge   Send PM to GoldenAge
 
youngbat Profile
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Caped Crusader

Registered: 02-2004
Posts: 1182
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Re: Parting agents - help !?!


Not sure if I understand the problem, but usuming I do, I will try to answer.
Usually using a polymer/plaster dirivative will cause what I call a "vacumn lock". It will seem as though the mold was glued to the clay. One solution is (next time) to divide your molds in more than 2 places, i.e. 4 part mold instead of a two part mold. If you are running slip latex as your finished piece, I would switch to hydrocal or ultracal. You can substitue water in either with a milk-like material calle "aycrl 60" a cement hardener. This will increase the life of the mold. Make sure to agitate the plaster with a very fast mixer, and weigh out the water/acyrl 60 to plaster ratio. This avoids the possibility of mixing it too thin, or too thick. Have several buckets ready to go so you can immediately follow one coat with the next, without trying to bust your butt trying to get the next bucket ready for the next coat. The polymer/plaster stuff doesn't suck up enough water to consistantly make good latex skins, at least the types I have used. Remember strength of plaster has a lot to do with how you mix, and apply it. I have seen some really excellent super strong, surface tough molds made with nothing but hydrocal and water, as opposed to chalky, brittle, and where the inside layer flakes off after a few pulls that can happen when the hydrocal is not used properly.
3/7/2004, 11:38 am Link to this post Send Email to youngbat   Send PM to youngbat
 
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Caped Crusader

Registered: 02-2004
Location: london
Posts: 1262
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Re: Parting agents - help !?!


thanks muchly YB - but my problem is getting the mold off the sculpt, not the latex out of the mold... (luckily I don't have that to look forward to.) It's the sculpt thats made of plaster. (+ newclay)

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Caped Crusader

Registered: 02-2004
Posts: 1182
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Re: Parting agents - help !?!


Are you saying that you coated the sculpture with plaster?, then applied a parting agent to the plaster? I'm not getin' a clear picture of what you did. What was the name of this water based release? You need something that will create a good barrier coat such as Johnson's paste wax. You can get various waxes that are specifically mold release waxes, but over the years I prefer Johnson's to just about anything I have tried.
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cursedbat Profile
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Apprentice

Registered: 02-2004
Posts: 297
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Re: Parting agents - help !?!


Paste wax is the way to go I didnt understand that your sculpt was solid and you are doing hard sculpting. Under certain applications you can also use zinc stearate which can be found in a spray. If you molded it big you can get a real good pull all seamed and recast it into a one piece master mold for future use also bro.

---
Dont disrespect the archetype with the pathetic sides of the human condition


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