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Starting with casting...


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#1 Cybrasty

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Posted 25 October 2018 - 05:15 PM

Hi all!

 

I am new here, just getting into mini figures and I love their aesthetic.

 

I am decently skilled in 3D modelling and have some background in art. I have done casting, but only in plaster and concrete and on a much larger scale. So before I jump into modeling and buying materials I have few questions.

 

  1. What silicone are people using for their casts? Are there any recommended brands? Any to avoid?
  2. I really like the rubbery minis, so this is what I would like to start with. Again - any recommended brands, or ones that are close to any established figure brands (MUSCLE, Monster in my pocket, etc.)
  3. Looking at the customs over here, it seems they were sculpted mostly by hand. While hand sculpting is something I would like to get into, I was wondering has anyone done casts of 3d prints (e.g. printing in high detail smooth resin) and making a mold from that. I don't expect this being an issue, but I would be interested in experiences of others.

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#2 sanjeev

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Posted 26 October 2018 - 07:52 AM

I can't speak on the topic of casting, as I don't do that myself. But I can certainly say that 3D modeling/printing works! All the keshi projects I've been privileged to be a part of have involved my 3D designs being printed in high-res plastic, then molded in silicone.

 

You just need to keep in mind the limitations inherent in casting when you do your modeling. I know the temptation with 3D modeling is to recreate the exact vision you have in your head...but you really have to balance that out with the realities of where your practical castings skills are at...


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#3 Cybrasty

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Posted 26 October 2018 - 11:45 AM

Thanks for the info sanjeev. I am glad that my 3d printing idea will work.

As for casting - because I have never cast in this scale or material for my first sculpt I will go pretty chunky and with as few protrusions as possible. I have couple ideas for characters like that, so it shouldn't be too bad.  


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#4 Ericnilla

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Posted 26 October 2018 - 12:27 PM

Smooth-on has everything you need.

Oomoo 30 (or 25) silicone is cheap and easy to use, get a trial size on Amazon for $30 shipped.

Smooth-on has a few Casting rubbers, task-16 and Simpact-85a are easy to use. Buy through Reynolds Advanced Materials.

Edited by Ericnilla, 26 October 2018 - 12:27 PM.

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#5 Cybrasty

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Posted 26 October 2018 - 03:27 PM

Thanks Ericnilla! That gives me a good starting point.


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#6 Cybrasty

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Posted 28 October 2018 - 01:27 PM

Another questions for the casters here: are you using 2 part molds as standard? Or is it common to cast in one block and cut?

 

As for pressure pots / vacuum chambers - They seem pretty pricey to start with. Can I get by without them when casting opaque rubber? 


Edited by Cybrasty, 28 October 2018 - 02:01 PM.

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#7 Ericnilla

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Posted 29 October 2018 - 10:12 PM

Rubber always requires a pressure pot, it's a lot thicker viscosity, you will always get bubbles.

And it depends on the figure complexity, I always do 2 part molds because I'm never in a hurry, people that mold a lot and fast like retroband do block molds. The molds last longer too, as long as you use a release spray.
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#8 Cybrasty

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Posted 04 November 2018 - 08:04 AM

Will pressure pot fix air bubbles in rubber? I thought pressure pot will just shrink the bubbles under pressure and they will expand once you remove them (because rubber is flexible).

 

Also, Is task-16 and/or Simpact-85a more like MUSCLE or Keshi in its finish? I am looking for more of a MUSCLE finish, more rigid than Keshi rubber.


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#9 Ericnilla

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Posted 04 November 2018 - 03:37 PM

Closer to Keshi rubber, Simpact-85a task are 70a-85a durometer. Muscle is closer to 95a durometer.

Pressure pot pushes rubber into the mold and squeezes out bubbles. Once cured the bubbles don't expand, did someone tell you that?

But do remember that rubber is harder to work with and harder to have bubble free casting

Edited by Ericnilla, 04 November 2018 - 03:38 PM.

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#10 Cybrasty

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Posted 04 November 2018 - 03:44 PM

I did some googling on vacuum chambers and pressure pots, and that's where I found the info that the air can return to the compressed bubbles once the pressure is removed. It made sense to me.

 

Is there any casting rubber that is closer to MUSCLE that is relatively easy to work with? Technically it doesn't need to be a rubber, I am happy with a plastic that has a similar flexibility and "feel."

 

Is durometer a unit to measure rubber rigidity?

 

Sorry for the torrent of questions, never worked with rubber before, just some generic art-store level plasters and resins. 


Edited by Cybrasty, 04 November 2018 - 03:56 PM.

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#11 Ericnilla

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Posted 04 November 2018 - 04:23 PM

Clear flex 95 is close to muscle rubber but is hard to use because you need to cast at room temperature 70°+, and you need to use a respirator since the fumes are hazardous.

And as resin goes I wouldn't know I don't use it that often
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#12 Cybrasty

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Posted 04 November 2018 - 04:27 PM

Clear flex 95 is close to muscle rubber but is hard to use because you need to cast at room temperature 70°+,

 

Hehe, now I see why so many casters are from California ;) 

 

Thanks for all the info. I will go research some resins and plastics, maybe I can find something with that MUSCLE feel...


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#13 Ericnilla

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Posted 04 November 2018 - 04:28 PM

Durometer scale

Attached File  durometerchart.png   156.17K   16 downloads

There are plenty of semi-rigid resins available from smooth on but like I said I've never used them
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#14 Ericnilla

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Posted 04 November 2018 - 04:31 PM

Also watch out and read carefully because certain urethane Plastics can only be casted in tin silicone, not Platinum based.
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#15 Cybrasty

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Posted 04 November 2018 - 04:38 PM

Man, thank you so much for all this info. I owe you a beer!

 

Time to dig-in into smooth on website and look at some resins. 


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#16 Cybrasty

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Posted 04 November 2018 - 05:02 PM

One more question - when I see number followed by A or D it relates to the Durometer scale, even for plastics, right?

 

Edit: Found the answer, most of the time it is YES, but it is always good to check the documentation on the manufacturer's website.

 

After some digging and more research I think I will start with Simpact 85A. It is as hard as a shoe sole, which is probably not as hard as MUSCLE, but definitely harder than some of the super-squishy Keshi I have. I should probably start with something a bit easier to cast coming from one part casts with simple materials. Once I get the hang of it I will move to something like Smooth Cast 65D. 


Edited by Cybrasty, 04 November 2018 - 06:58 PM.

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