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Stronger terrain model substance

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Recently, I tried making model rocks and terrain with a mold.  I poured in a mixture of Hydrocal Plaster into rubber molds and the results were great.  The shape and detail was exactly what I wanted.




But the problem -- it was Hydrocal Plaster  powder, mixed with water.  When it dries/cures it's still plaster and therefore a bit chalky and fragile.


I broke a couple in half trying to get them out of the rubber mold.


I can only foresee a problem trying to use them (fragments of them) on bases.  I can imagine the jostling around in the Army Box will chip away and break off corners. 


I'm looking for an alternative way to cast molds so that the product is stronger, not susceptible to chipping and cracking (something stronger and more durable than 'plaster')


What materials are in the market that achieve that?  What should I mix and pour instead of 'Hydrocal Plaster' ? 


Thanks for your help/ideas



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Have you tried running wet toilet paper in a blender and mix that in? The paper fibers will strengthen the plaster mixture.


Another option is tho use acrylic resin powder instead of plaster. Green stuff world sells this one that I have tried with good results:



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Would it work if you mix a tiiiiiny bit of pva into the mix? Might not work its just an idea that popped into my head.

Or a thin layer of superglue over the rocks, just to give it a tougher top layer. 

Edited by Slave to Darkness
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  • 1 month later...

What Slave said - you should try adding PVA glue to the mix, and it’ll help with durability. I don’t remember exact proportions.


Paper fibres are also a good idea, although I think that if you pulp them, it might not be as useful to the structural integrity, ideally you want longer fibres in there. Maybe try looking for hemp fibres?

you can also try adding medical gauze before pouring.

a side effect of these additions is that is you might get fibres sticking out of the casting, but if they’re natural fibres you can burn them off.

Also, add ink, paint or dye to the mixture, to turn it the rock colour you want. this way if your rock chips, it’ll be much less noticeable.


A higher proportion of plaster vs water also yields a denser less crumbly end product.

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  • 9 months later...

A word of warning before reading my advice, I dove into playing with molten metals with safety knowledge already ingrained and this is not for the skittish or clumsy.  That said, read on if you are curious or dare I say... (dare, dare) ...interested. Sorry, Blazing Saddles reference after that last conjunction.


As someone working on metal 40K projects right now, you can cast those in a firm wax or in a lower melting point plastic or resin, then using sand casting pour some pewter over it and now your terrain is probably the most durable 40K you will be adding from this point on.  At a melting point of ~250C you can easily melt it at home, just wear a respirator, proper attire, and have excellent ventilation.  Also, the pot you use will forever be unfit for cooking so try to not use that cast iron cookware the spouse/parent/etc just bought.  For a more Warp flavored set use bismuth instead.  A high purity will get you a wonderful iridescent set of rocks that scream Warp terrain, you just need to wait a few days for it to oxidize. 


Edit: Given my avatar, I have to add:  You will have the strongest terrain in Gensokyo.

Edited by FashaTheDog
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  • 5 months later...
On 12/19/2022 at 11:09 AM, Maschinenpriester said:

 I did some casting with Stewalin. 

I dont know what the difference to regular plaster is though.

it feels tougher to me though.

Stewalin is more ceramic as far as i understand it.

However, i can recommend it. I used it for casting of architectual details after a dozen of failed attempts with plaster - and that really worked like a charm.

MUCH harder and durable than plaster - and even in enclosed moulds, it hardens within hours.

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