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Searching for the perfect resin

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Searching for the perfect resin

Postby ukoku » Sat Jan 01, 2011 10:58 am

I'm searching for a resin that has specific properties. Most of what I need can be done with polyurethane...except that it's toxic. I'm searching for one that isn't.

I need the final product to...
...have a Porcelain-like feel (rather than a plastic one)
...be similarly durable (or moreso)
...be sandable
...have a white color
...but can be optionally colored
...be good for painting on
...be cold-casted with a two-part mold
...be non-toxic (at least once finished)

I can find lots of kinds that fill SOME of these, but I'd like all of them.

Anyone have any recommendations? Or can point me in the right direction?
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Re: Searching for the perfect resin

Postby blind pig » Sat Jan 01, 2011 11:47 am

Your best bet would be to talk to a knowledgeable person at your local resin supply store. Resins vary greatly from country to country, so you need a bit of local knowledge.

Many polyurethanes can be altered to give a more "stone-like" feel with the addition of crushed minerals like talc, marble or mica.

I regularly use talc (babypowder) as a filler for large resin models, to thicken it so it adheres to the wall of the silicone mould, but still takes the usual 3-5 minutes to gel and cure. It also cuts costs, as at upto 20% talc by weight, it fills a large mould at a reduced cost. Talc is about $1 a Kilo, bought in 30Kg bags.

Adding talc does make the polyurethane slightly softer at 30% by weight, but dosen't really alter the "feel" much. I guess if you add talc (or hell, can you get porcelain powder?) at 50-75%, it would be quite a different feel to the usual polyurethane, but would be softer and may even able to be marked with a thumbnail.

I'll give it a go at various % of talc and let you know.

Bec
Last edited by blind pig on Sat Jan 01, 2011 12:30 pm, edited 1 time in total.
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Re: Searching for the perfect resin

Postby blind pig » Sat Jan 01, 2011 12:29 pm

Well, that was a bit of a failure. :(

At my usual 20% talc with a Polyurethane called 4PU it is not really any different to the usual product - mabey a little more brittle.

At 40% talc it was a custard-like consistency and didn't fill all the voids like the normal 20% talc would. It was a fair bit softer and felt a little porus.

At 50% talc it was like toothpaste and had to be pushed into the mould,it foamed a little (could be the humid weather) but has a greater feeling of being porus.

At 60% it was too thick to stir and mix before the resin set.

*as a bit of a side thought, have you tried altering the finish of the dolls skin? A smooth doll that is cast with silicone resin will pretty much always give a smooth finish, no matter what the filler used (unless it was really coarse). What would happen if you were to give a smooth doll a light sandblasted finish before casting with silicone? That light sandblasted roughness would be transfered into whatever silicone mould you used and would be reproduced into the final product. It wouldn't have the "cold" feeling that a porclain doll would have though when touched.

[edit] Or do what Paulson suggests and spray on a slightly rough finish.
Last edited by blind pig on Sat Jan 01, 2011 7:18 pm, edited 2 times in total.
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Re: Searching for the perfect resin

Postby paulson games » Sat Jan 01, 2011 6:57 pm

I'd try the micromark cr-300 or their cr-600 it has most of the properties you are looking for. The material strength will depend on how thick the parts are, thin parts in any form of resin often tend to be weaker either producing something that is rubbery or brittle. (but those are very small parts)

Both of their resins cure to a pure white color and can also be dyed. I wouldn't use micromark's dye however as I've had problems with it. Allumilite makes great dye that from first hand experience I know also works well with mircomark and smooth-on resins. Most companies have material data explaining the durability and shore hardness of their materials. There are some resins out there that are used by artists to create custom GI Joes or other dolls and action figures that are incredibly tough rivaling actual plastics. I don't know what brands to suggest off hand but some goole searching for custom action figure construction will probably turn up some leads.

As far as a porcelin like finish the best way to accheive that is by having that texture in palce on the master model before casting it, silicon and the resin will pick up whatever surface feel that the original part has. The best way to capture the texture would likely to have the master part base coated with either a primer or a surfacer paint, that can be worked to whatever degree of texture you need anything from a grit to a smooth sheen.

There's a Japanese product called Mr. Surfacer which they sell at most hobby stores that would have Tamiya or MIG line products, and it can also be ordered online. I think hobby link japan has some available through their website (http://www.hlj.com)

Surfacer combined with modelling grade ultra fine sand paper you can get a wide array of results on surface texture.
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