Silicone Rubber temperature tolerance

[ManicMan]

In the past I've messed about with Polycraft's Red and White Silicone stuff, which makes Pink moulds.. and some stuff which is white and I think its kinda awful cause.. you are mixing white silicon with clear Catalyst so it's bloody awful trying to see how well mixed the stuff is.. I've also used some kinda blue stuff which.. I think they just call 'Blue Stuff' which is a kinda fast setting Silicone rubber..

anyway.. I'm wondering what kinda temperatures that can withstand. It's just I've decided to do a bit of messing around with Metal casting via Prince August's starter kits.. I got one cheap cause of minor damage to the outer box (does that matter?) and .. well, If you don't know, they were a Swiss company that became an Irish company who one of there main things was 'Why not save money by casting the figures yourself?'.. they do more then just miniatures but they do a range of them as both ready made minis, or moulds.. there moulds are vulcanised rubber but they also say about making silicone moulds in the normal 2 part mixture way and sell some silicone to do this.. clearly, those moulds wouldn't last as long and this kinda metal casting isn't a good as a spin caster or anything (heat up metal, pour it into mould.. simple..) but it appeared fun enough ^_^ could buy a fancy melting pot or a hot plate, or just use home cooker for there '6 star' metal (which is erm.. 40% tin and 60% Bismuth).. a simple white metal with a melting temp of about 140c and a casting temp of about 300c)..

the set I brought, I got partly cause the moulds were the most interesting of the ones they sold and for a good price.. though I can't say I think they are really my tastes.. It's mostly for me to screw around and see how things go.. But I was wondering about some of the silicone I got if they would be any good for casting the metal in.. would be a bit more interesting (I've been trying to sculpt swords.. and I got a couple of minis I've been toying with.. might be fun to have a try of casting a bit but it's just a bit of fun ^_^, hell if I'm any good or really wanna put in the effort and time to make sculpting a major thing... Just good enough to do the odd customising and repair is fine with me.

Anyway.. while it probably matters what type.. anyone has any clue? some tech information I find doesn't seam to wanna go into any information ¬_¬

 

[Fimm McCool]

The silicone will stand up to the heat for a few pours, but let it rest well between as if it gets too hot the surface will start to get brittle. The really important thing if you're drop casting (just pouring metal from a ladle) is to have a deep pour channel as you're relying on the weight of the metal to press into the details. Use chalk or talc to draw the metal into fine parts of the mould. Make sure that any narrow/fine parts of the model are pointing away from the pour channel and be prepared to mess (carefully) around with a scalpel to vent any bits which don't cast well. You'll probably only get 20-30 casts out (depending on shape, size and detail) before the mould wears out.

RTV silicone is available in lots of different shore hardnesses. I would go for a tin/condensation cure around Shore A 45-50 for lead casting.

 

[ManicMan]

Thanks ^_^

I'm not sure how much silicone I got at the moment or what type.. probebly some of the blue stuff..

yep, the kit comes with 'release agent'.. which is Talc.. they say it's there 'fine' talc cause you don't want to use more lumpy stuff, which is true. There metal aren't to bad a price for home hobbyist more then full production scale which is the point.. Shame they are in Ireland.. they even do Birthday parties at there workshop where you can cast, paint and stuff miniatures ^_^ sounds fun.

basically, they do "6 star" metal, which is Tin-Bismuth (40-60%), "5 star" metal (94.5% tin, 3% zinc, 2.5% Antimony.. which I've never heard of), 'Model Metal'(54% Lead, 11% Tin, 35% Bismuth), and 'Standard' (65% lead, 2% of that Antimony and 33% tin) as well as some odd bits like Lead bits and stuff. But for screwing around, it seams the 6 star is the better one (what I mean by not too bad a price is basically £5.50 for a bar which can do about 10 figures.. not on the price side of more bulk (you do save some if you buy more from them) but it's home hobby more then a bigger scale like you ^_^ or even a bigger one like.. well, some huge company.

 

[Fimm McCool]

The lead free metal will tear moulds quicker, but is safer for heating over a stove. Charity shop pewter tankards etc. are pretty good to melt down and use as they're a softer alloy which flows into detail better. Watch you don't boil them, but as you need to heat in excess of 400 degrees to do that you're probably safe.

'Blue' isn't a type of silicone sadly, all manufacturers have their own colour coding and sometimes change it. The tin RTV I get from EasyComposites used to be blue, then it was pink for a while, now it's grey. Same formula, different dye.

 

[ManicMan]

I think they call it 'Blue stuff' ^_^ Ah. no, they are stupid.. "Blu-stuff'.. but it looks like.. they have gone out of business as there website is now up for sale.. It's a 50-50 mix with a fast cure rate.

Hopefully I'll have a test of doing the 3 models the kit comes with (Orc Stormtroopers from the Fantasy range) this week and see how it goes. 25mm.. meant to be 'armoured orcs bigger then the normal'.. only shows drawing which... the style reminds me of something.. mm.. not quite Bakshi.. look kinda more Lizard like..

 

[ManicMan]

not quite sure the best place but might as well here.. but.. did my first test casting with the mould it comes with.
From the foot (since they come with solid bases, I'm going from the Foot more then the base) to the top of the helmet is about 27mm, they are slightly crouching pose:

photo isn't fantastic of course, and it might the mould lines look a bit more then they are, but they come out perfectly.. more so then expected for my first go. Not quite my taste of Orcs but fair enough (big shame they don't credit sculpture.. I think it used a bit more metal then I expected but it was an average of 9-10 figures, and the plugs can just be melted down again and I still got some metal left anyway so pretty sure 100% I can get another 3 of these if I wanted and maybe a couple of more so.. not too far off or anything. I'm probably gonna see what old silicone moulds I've made up in the past (or make a new one) to try out casting something that isn't from a pre-made mould next.. these do have a very early 80s feel to the designs.

EDIT: I think the sculpture was 'Chris Tubb'... can't say the name rings a bell or anything though.

 

[Fimm McCool]

Pretty much as good as you're gonna get from those moulds.

 

[ManicMan]

I think they turned out pretty well, pretty much no mould lines on the figures, detail appears all there, not quite to my taste in design but that's the design more then anything else. wouldn't be able to do the same quality as spin casting or anything but still really good ^_^ so it's good my first attempt came out soo well.

 

[Fimm McCool]

Indeed. The design is kinda essential for these drop cast figures. They can't have spindly bits or complex poses as there isn't the force to throw the metal into the extremities. I think you've done a great job getting those results.

 

[Firstruleoffightclub]

You need the red silicone stuff for metal gravity casts .

 

[Fimm McCool]

You need the red silicone stuff for metal gravity casts .

Different manufacturers supply differently coloured catalysts, so it won't always be red.

 

[ManicMan]

I've done pretty well with a couple of types though annoying the last lot of Silcone I brought turned out to be what I call horrible stuff.. white with clear catalyst.. a bugger to be sure it's mixed right ¬_¬
apart from the odd bit of steam on the first cast, and having to be even more careful to get the chalkdust coated to reduce surface tension, it's not be bad.. Haven't done a whole lot as haven't the need right now but still.