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"plaster of paris minimum thickness?" Topic

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wardog12 Feb 2017 12:36 p.m. PST

i made a silicone press mold and was was thinking of using plaster of paris for my pour,so was wondering how thin can plaster of paris be before breaking (note part of the master i created was couple of mm thick) could not make it thicker without making it weird looking,
anything i could add to the plaster to make it stronger?

GarrisonMiniatures12 Feb 2017 1:00 p.m. PST

It's stronger if you add wood glue to the mix. Washing up liquid will make it flow better. You can add things like fibre glass to make it stronger but that will have a major effect on the flow properties. I suspect 'a couple of mm' is always going to be a bit too thin though. Have you considered resin?

JimDuncanUK12 Feb 2017 1:00 p.m. PST

Don't use plaster of paris.

Use a dental plaster instead.

GildasFacit Sponsoring Member of TMP12 Feb 2017 2:17 p.m. PST

Neither will be very strong and there are much stronger plasters on the market but you need to see what a specialist supplier has, art and craft shops don't sell the good stuff.

Most plasters are hard but not tough, a small amount of bending will snap even strong plasters. Additives can improve the toughness and make them a bit flexible – again look at a specialist supplier (e.g. Alex Tiranti in the UK).

PVA can work (in small proportions – a few %) but slows down drying time quite considerably.

Ran The Cid12 Feb 2017 3:00 p.m. PST

durham's water putty is available at most hardware stores. It is much stronger than plaster of paris and good for little projects like this where you just need a few grams.

Thickness of your cast should be at least 1/8 inch. That will be pretty fragile, but will hold up if you are attaching it to a backing material.

Mako1112 Feb 2017 6:18 p.m. PST

Resin will work.

I wouldn't go much thinner than 1/4", and that will be fragile.

3/8ths, or 1/2" would probably be better.

WeeSparky12 Feb 2017 6:32 p.m. PST

Acrylic Concrete Fortifier, found at all major DIY stores (Home Depot, Menards, Lowes).

Greylegion12 Feb 2017 6:43 p.m. PST

Another vote for Durhams water putty.

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