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Help wanted with making a one-off mold

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Help wanted with making a one-off mold

Postby mickelsen » Thu Jan 03, 2013 1:25 pm

I'm making a one-off piece to modify a plastic model by making a mold using parts from the model itself and Sculpey modeling clay. It works great until I want to remove the Sculpey from the model parts. Can anyone tell me what I can use to clean it off but not damage the plastic parts it's been applied to? I've tried alcohol and soap and water but neither removes all of the clay from the surface. Acetone damages the surface of the model parts. I need something that will dissolve the Sulpey but not the polystyrene that the model parts are made from. HELP! Can anyone tell me what will work?

Thanks.
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Re: Help wanted with making a one-off mold

Postby Sub culture » Thu Jan 03, 2013 1:41 pm

Different approach- you can apply some PVA to the item you are moulding. This will put a thin film over the part, when you pull the sculpey away, the film should pull away with it, then just clean up residue with water.

Fibreglass suppliers should be able to sell you PVA.

Another thing you could try is to wipe some vaseline over the part being moulded, I find that works well with plaster, and quick and dirty moulds with bondo, but haven't tried it with sculpey. Try it on a bit of scrap first.
Last edited by Sub culture on Sat Jan 05, 2013 3:08 pm, edited 1 time in total.
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Re: Help wanted with making a one-off mold

Postby mickelsen » Fri Jan 04, 2013 6:03 pm

Thanks for the idea, SubCulture. But I worry about one thing. When I apply the Sculpey to the plastic parts to make the mold, I need the Sculpey to stick. I can't haven't it sliding around or have the Alumilite seep under it. (I'm using the one-off mold to cast Alumilite parts.) That's why I was hoping to dissolve the Sculpey to remove it afterward. Does anyone have a better approach, either to making the mold in the first place or cleaning the mold afterward?
Thanks again.
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Re: Help wanted with making a one-off mold

Postby Sub culture » Sat Jan 05, 2013 10:47 am

I'm afraid you've lost me a little now. Can you post a picture or two of exactly what it is you're trying to cast.

There are various materials you can use for one-shot moulds. I've used candle wax for making small items, which will hold for a few pulls, then it begins to burn out, as the heat from the resins curing process begins to effect the surface of the wax mould (more of an issue with polyester and polyurethane than epoxy resin). I just melt the wax back down, repour the mould and off you go again. As it's wax, it is self-releasing from any resin, so no prep needed on the master or the tool for subsequent castings.

If the object has any undercuts, then this method won't work, as the original item will lock in, and the wax has no flexibility to pull clear. You can get a hot melt vinyl material called vinylmold. This is a material that can be heated up in an oven or saucepan of water to a fluid/gooey state, and poured over the master. When it cools it forms a flexible tool which can be used over and over, like a rubber moulding. Once you're done, you can cut the vinyl up, remlt it into a new tool.

It's rather like the wax method, but becuase it's flexible, the original can have sharp undercuts, and you can just peel it away. It's available in different grades, from super soft to something quite firm.

Can't recommend a US supplier. I got mine from Titanti in the UK.

http://www.tiranti.co.uk/EdgeImpactShop ... cillaries+
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Re: Help wanted with making a one-off mold

Postby kazzer » Sat Jan 05, 2013 1:34 pm

I don't know about Skulpey, but I use Alumilite's Modeling clay, (because we sell it), which I presume is very similar. These materials are made of a fine clay mixed with an oil. The clay will dissolve in water, and a detergent will dissolve the oil. Soap is different to detergent and if you have used that, I'd not be surprised it doesn't work. If you use some detergent like dish washing liquid and an electric toothbrush, you should have no trouble. Wash it down with hot water and more detergent.

If you make sure the area is very clean before you apply clay, I can't see you having a problem with it sticking. Soften it up either with a few seconds in a microwave, or immersed in hot water, then smear on a thin layer prior to building up.
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Re: Help wanted with making a one-off mold

Postby salmon » Sat Jan 05, 2013 2:21 pm

Sculpey is different than modeling clay in that when baked becomes hard. It is a polymer clay, a plastic clay. So any material that dissolves it, will attack your plastic model. You might even notice sculptey will eat into the model itself leaving a flat, etched look behind. For me, rubbing it off and scrubbing with a toothbrush and dish soap is the best way to remove the sculpey left behind. I am not sure how practical this suggestion will be, but how tough would it be to cast your model in resin? Then use sculpey on that?
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