TUTORIAL: Making Moulds and Casts

obar

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Gorkamunda said:
OBAR! FEMALE VAN SAAR! CAST! NOW!

Oh, right. That thing. Well I certainly know how to do it now. But I'm guessing you want that last arm done first? I'm almost done moving stuff so I might have time
 

The Castle

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i dealt with quite a few things like that at the paint/sundry warehouse. i can't expect the CMON stuff is too much different than the more "industrial" stuff that you can find in the plumbing section of a hardware store. probably cheaper than the CMON stuff since it's less niche marketing. just a thought.
 
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cardyfreak

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That is ridiculously expensive. Epoxy resin will work, it just takes longer to fully cure. And I'm not sure how well it work in two part moulds but in open faced moulds it should be fine. But The Castle is right, DIY shop stuff should work just as well. It might be a bit thick but should do the job for things like bases and what not. Again though, it's more expensive than a decent sized bottle of polyurethane.
 

FluffyBunny

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I did a fair bit of casting with plaster and latex a way back selling terrain on ebay. Used the remaining bits for the crystal dome campaign if you want to see the end result. Here's my 2 cents.

Plaster is dirt cheap and works for terrain just fine
Coat the plaster with PVA glue (wood glue) before painting or else it looks pastel coloured
You can dye the plaster so that any chips and scratches aren't as noticeable
Metal will 'poison' the latex so don't make any models out of metal unless you only intend to use it quickly.
if your model is made of card as most of mine were coat it in PVA glue first - makes removing it from the latex mold much easier
Latex itself can be used as the 'end product' rather than just as a mold - my ladders are made from a think layer of latex poured onto a card mold.
1cm is a good thickness for the walls of buildings, ours are 18 inches tall and stable.
latex is cheap enough and harmless enough that you can paint a few layers on anything and see what mold is produced - often the latex itself tunes out to be a useful model.
latex shrinks so make sure your model is solid of the end mold will be distorted.
Plaster models are too heavy to make selling on ebay viable and I should have gone with laser cut mdf.
Sealing/insulation foam may be worth investigating as an alternative filler.
 
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cardyfreak

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Hi Cardy

I'm wanting to make box hills with cast bulkhead edges kinda like this http://www.warseer.com/forums/showt...og-Sci-Fi-Industrial-Necromunda-Inc-Timelapse

I've never cast anything before so my question is, is this a good place to start? Or am I being a little over ambitious? I want to make 4 x 18 inch squares so that's a 100 one sided bulkheads.......any advice appreciated!
It's really easy to cast bulkheads, you just have to make sure the silicone can't flow around the edges and underneath it. I'd recommend following the steps for making a two part mould, only doing the first pour and not the second. The result will be an open faced mould. You won't have to bother with the keying as it isn't a two parter. The bulkhead should be embedded into the plasticine deep enough to prevent silicone seeping underneath it. If your just casting the solid bulkheads this will be very easy as the only way it can get through is around the sides. The Gothic arch, door way and fan are a bit trickier. The door one is the easiest, you can simply glue a piece of plasticard to the reverse side of the doorway. If you add some hinges and a handle, a viewing slit, maybe some rivets, it'll look like a closed door. The other two are a bit trickier, but you might get away with gluing some plasticard over the back to blank it off like the doorway one, that'll preserve the detail. The detail just might be a bit thin and fragile immediately after it's set, so take care when demoulding, as the silicone might seep around the transoms and mullions of the arches, and the fan blade thingies of the fan one. This can be sorted easily when you demould the mould for the first time. A sharp knife to widen the channels will suffice. This will allow the resin/plaster to flow through the small channels easily.
Another note, if your going to be casting using plaster, make a surfactant bath to dip the moulds in. A surfactant breaks the surface tension of the plaster allowing it to fill the mould with fewer air bubbles. I use dish washer rinse agent and water. Just squirt a bit into a bowl of water and dip the moulds in.
For the amount you'll be casting it'll be far cheaper to use plaster, it'll be slower though as the plaster takes longer to set. The more moulds you make though, the faster it'll be!
Hope this helps!
Ps, if at any stage you need some advice on how to proceed, either stick it up here or PM me (photos of copyrighted stuff being copied might incur wrath onto the site so be wary!) and I'd be glad to help in anyway I can!
 

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Thanks for the swift reply!

Last question do you reckon a cast 6 bulkheads long would work? i.e. One side of a hill?
 

cardyfreak

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Thanks for the swift reply!

Last question do you reckon a cast 6 bulkheads long would work? i.e. One side of a hill?
Mate, if you've got the silicone to make it, it'll work. As long as that's a workable size then do it. If you think you'll get more versatility out of two three-long moulds then do it that way. Takes more silicone though. It's entirely up to you, and the materials you have at your disposal. Out of curiosity, which material will you be casting with?
 

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Rusty101

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Cardy, have you any info on materials to cast in. I've heard many different suggestions on different plasters and resins, but no real world experience. Hard dental plaster seems like a good option, but weight might be an issue on the long run, if casting loads.

I ask as I've just bought some hirst art moulds and should be casting up pretty soon.
 

nooker

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I hear dental something or other is good, but don't have personal experience. Hirst Arts mostly sells molds and has a lot of instructions and a large community. I would check there as they have been at it for a while.
 

cardyfreak

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Cardy, have you any info on materials to cast in. I've heard many different suggestions on different plasters and resins, but no real world experience. Hard dental plaster seems like a good option, but weight might be an issue on the long run, if casting loads.

I ask as I've just bought some hirst art moulds and should be casting up pretty soon.

Basically if the plaster has the words 'die' or 'stone' in its name it'll set hard. Generally you aren't going to need really fine detail capture when you cast things with plaster as they will still be quite brittle. But good thick things like pipes or bricks just need to be hard. And although it's weightier than resin, it shouldn't be too much of a problem.
 
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FluffyBunny

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yeah the weight isnt too much of a problem. we have 15 inch tall towers and they stay stable and can handles its own weight.
i bought the 25kg sacks, £5 each, works fine and detailed enough for grains of sand.
you could dye it grey etc with a little ink so any chips are not as noticeable.
depending on teh shape of the mold you can mix the centre of it with polystyrene balls, i did for my larger projects, such as the body of this.

Titan%201_zps0vjpsyoy.jpg
 

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