TUTORIAL: Making Moulds and Casts

undertaker

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Oct 21, 2016
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Can I just cheekily drop this product link in here. I have no affiliation or anything like that.

It is however a resin casting powder, 3:1 mix powder and water so a lot easier to mix up a tiny amount and bring far more liquid when mixed it gets into your molds easier!!

Mods delete link if inappropriate.

http://www.greenstuffworld.com/en/mold-making/718-acrylic-resin.html

It seems like that "resin" powder is a type of dental stone. Like plaster of Paris, but harder. You can see more on this Hirst Arts page:
http://www.hirstarts.com/casting/dental.html

I've never used it, but it seems great for 1-part moulds, like they demonstrate in this video:

Using it for 2-part moulds seems like a nightmare though. You'd have to fill the two halves separately, let them partially cure so that it stiffens up a bit, and then slap them together. Tricky. Especially since a 2-part mould is rarely in two neat halves with edges all at the same elevation. Usually some parts are lower than others, with the seam not horizontal relative to the table. So you would fill the mould, and some of the liquid would proceed to dribble out. A putty seems better suited for the purpose.

Maybe I'm wrong. I should get some and find out, really. :whistle:
 

MusingWarboss

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Wow! Thanks @undertaker! I'm mostly interested at casting one part press molds of stuff for basing, though now I might take another look at Hirst again, never liked the idea plaster of Paris as its too easily chipped. These dental plasters look great and would help with my idea to totally not recast a few sector mechanicus walkways to sit astride my own scenery. :whistle:
 

trollmeat

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Have somehow missed this thread until now. Will have to go back and like-spam the first half later :)

I have some Polymorph Pellets, which are similar to oyumaru/blue stuff except that it doesn’t retain any flex when hardened. They worked really well for getting some face moulds (for minis, not people), some tyres and other rubble that I wanted duplicated, and for when I needed a handle for an outdoor tap.

I will have to get some oyumaru/bs so that any future moulds can “hug” the minis. :)
 
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undertaker

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It's tricky to get some parts out if the mould does not flex. Not much of a problem for 1-part moulds, but for 2-part you would have to be very careful that the mould does not overlap protrusions in the part at any point and stops you being able to take it out. With oyumru you can just flex the mould to pop the part out, rather than having to prise it out without breaking it.
 
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ClockworkOrange

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@trollmeat (it’s good to see you!) I’m late to this party also and have just started with Blue Stuff. TBH if you follow the tips here it’s bloody easy, this was my first attempt:

50A0E8E7-E34F-4568-9D66-111EC1389EFB.jpeg

EB8A4C1D-6DAB-4DF4-BA98-2C23F1223BF1.jpeg


I’m using Green Stuff while I wait for some milliput to turn up. I’ve tried a load more things tonight, going to see how they turn out in the morning.
 

Petitioner's City

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Wee question for @cardyfreak and the other venerable experts here; if wanting to cast an already-built ZM bulkhead or wall in plaster, would you recommend a single side mould (much like the two barriers in the original example, with the item standing upright in the chamber) or a two-sided mould (with the wall or bulkhead on its side)? They seem ideal for a single side mould, except each does have a slight overhang, so I'm not sure how to proceed.
 
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=][=SW1=][=

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I'd make a one piece mould with the wall upright like in the barrier example and then cut down the sides with a sharp knife if the casts don't come out easily due to overhangs. Then just wrap parcel tape around the mould to hold the cut edges closed before pouring the resin/plaster.
I prefer to make a mould that sits in a removable wall. So if you make a wall around the mould to form the mould in say lego and the slice the sides just stick it back in lego when you cast. You then don't get any issues of warpage that tends to happen if you try another method to keep the cut sides together. ;)
 

cardyfreak

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Wee question for @cardyfreak and the other venerable experts here; if wanting to cast an already-built ZM bulkhead or wall in plaster, would you recommend a single side mould (much like the two barriers in the original example, with the item standing upright in the chamber) or a two-sided mould (with the wall or bulkhead on its side)? They seem ideal for a single side mould, except each does have a slight overhang, so I'm not sure how to proceed.
Really it’ll depend on what you’re doing with it. If you’re just using it as detail to line a passage or wall or whatever and will only ever see one side then just do it as an open faced mould. If you want both sides visible then the way the guys have described would work if you didn’t want to go through the process of making a two-parter.
 
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Tiny

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I prefer to make a mould that sits in a removable wall. So if you make a wall around the mould to form the mould in say lego and the slice the sides just stick it back in lego when you cast. You then don't get any issues of warpage that tends to happen if you try another method to keep the cut sides together. ;)

Yeah this is more ideal tbh. The tape is more a quick and easy option. Depends how thick you make the walls of the mould too. I like to waste rubber making them way too thick. :)
 

=][=SW1=][=

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Yeah this is more ideal tbh. The tape is more a quick and easy option. Depends how thick you make the walls of the mould too. I like to waste rubber making them way too thick. :)
I like making them on the lean side but always cast with lego walls in place. Get more moulds out of any given amount of rubber that way. :)
 
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