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Hi! First time poster here, and first time miniature maker

I am looking for reasons not to go with latex for the molds but to go with silicone.
From what I have seen around the internet, silicone is the #1 choice.

However, in my country of Romania, latex is at least 3 times cheaper than silicone.

Is there an reason I SHOULD NOT go with latex?

I want to follow this tutorial:
https://www.youtube.com/watch?v=_87cjGF1eJA

Latex, while less expensive, breaks down much quicker and is not particularly suitable for anything with undercuts or for multi part molds as it is not nearly as flexible and is much more prone to tearing.

commissarbob wrote:
Latex, while less expensive, breaks down much quicker and is not particularly suitable for anything with undercuts or for multi part molds as it is not nearly as flexible and is much more prone to tearing.

I aim to make 2 half molds, then injecting the latex through a main hole until latex escapes through evacuation ports. I do aim to cast several small pieces of a body, or items from miniatures. Think D&D type miniatures, or even warhammer (any of them) but my gf makes them.

What does "breaks down much quicker" imply? I mean, on average, how many resin sessions can it take

On average a latex mold will start to break down, I.e. crack, lose surface detail, etc. after 5 pulls or so while a latex mold will last at least 40 to 50 pulls without degrading depending on undercuts, how aggressive the detail is, and how it was cut.

commissarbob wrote:
On average a latex mold will start to break down, I.e. crack, lose surface detail, etc. after 5 pulls or so while a latex mold will last at least 40 to 50 pulls without degrading depending on undercuts, how aggressive the detail is, and how it was cut.

you used the word latext in both examples I assume the second is silicone.

Yes, the second would be silicone, my apologies.

This is all of course also assuming that you are talking about a basic natural latex poured mold and not a vulcanized mold.

Regardless of what type of mold, one thing that will definitely make your casting more successful and increase your mold life is to powder your mold with fine talc, such as an unscented baby powder. This serves a double purpose of lubricating the mold and making it easier to pull the resin parts from the mold and it also breaks the surface tension of the mold allowing for a relatively bubble free casting even without the aid of a vacuum chamber or pressure pot, again assuming no under cuts.

commissarbob wrote:
Yes, the second would be silicone, my apologies.

This is all of course also assuming that you are talking about a basic natural latex poured mold and not a vulcanized mold.

Regardless of what type of mold, one thing that will definitely make your casting more successful and increase your mold life is to powder your mold with fine talc, such as an unscented baby powder. This serves a double purpose of lubricating the mold and making it easier to pull the resin parts from the mold and it also breaks the surface tension of the mold allowing for a relatively bubble free casting even without the aid of a vacuum chamber or pressure pot, again assuming no under cuts.

Can I use petroleum jelly to keep the two halves of the cast from fusing, for both silicone and latex?

Okay, Main problem with Latex is that it is air dried. Meaning, the outer layer will dry, and the inner will be wet (For A Long time)

Silicone on the other hand is self-drying meaning it will ALL dry at the same time.

Silicone has more stability, and keeps more fine detail

 MordorMiniatures wrote:
Okay, Main problem with Latex is that it is air dried. Meaning, the outer layer will dry, and the inner will be wet (For A Long time)

Silicone on the other hand is self-drying meaning it will ALL dry at the same time.

Silicone has more stability, and keeps more fine detail

From all of this I take it that despite the 3-4 times the price of latex, silicone is the superior solution. Are there types of silicone?

Oh yes, there are a variety of different silicones that have different properties. Some are super firm and have limited stretch and flexibility others are quite soft and extremely elastic. Some are even food safe, so if one wanted they could make chocolates in any given molded shape. I do not know what suppliers you would have access to in your region, so it is a little difficult to point you to a particular one without knowing what is available to you.

commissarbob wrote:
Oh yes, there are a variety of different silicones that have different properties. Some are super firm and have limited stretch and flexibility others are quite soft and extremely elastic. Some are even food safe, so if one wanted they could make chocolates in any given molded shape. I do not know what suppliers you would have access to in your region, so it is a little difficult to point you to a particular one without knowing what is available to you.

http://www.btools.ro/detalii_produs/12446352566383/rasina-poliuretanica-multicast-12.htm
http://www.btools.ro/detalii_produs/12440545344646/silicon-rtv-za-22-mould.htm

Does this help? You probably can't understand romanian but the latin science terms should be universal.

The mold ZA 22 type you linked to would be the most suitable of the silicones on the site. As for your earlier question about the petroleum jelly, I assume you are asking about pouring the halves separately? If so, yes. Pour your first half and let cure. Cut keys into the cured first portion. What I mean by keys are locating shapes such as channels or other shapes cut into the RTV. You then can spread a thin film of the petroleum jelly across the already poured RTV before the second pour. Those keys help you line up the mold halves securely and keep them where they need to be to prevent mold lines.

commissarbob wrote:
The mold ZA 22 type you linked to would be the most suitable of the silicones on the site. As for your earlier question about the petroleum jelly, I assume you are asking about pouring the halves separately? If so, yes. Pour your first half and let cure. Cut keys into the cured first portion. What I mean by keys are locating shapes such as channels or other shapes cut into the RTV. You then can spread a thin film of the petroleum jelly across the already poured RTV before the second pour. Those keys help you line up the mold halves securely and keep them where they need to be to prevent mold lines.

What about the resin, is that one proper?

That resin could work, though you may find the 6 type to work a little better due to lower viscosity. The lower viscosity means that the resin will flow into the details better and be less prone to hold bubbles. As far as the finished final resin goes however I am not sure as they do not discuss the cured resins shore hardness or flexibility so I will not be able to comment as to which would survive tabletop use better as some resins are extremely hard but brittle while others may be softer yet have a bit of give to them and are therefore less prone to breaking if dropped. You want to find a resin that has a low viscosity while pouring and strikes a good balance between hardness and flexibility.

commissarbob wrote:
That resin could work, though you may find the 6 type to work a little better due to lower viscosity. The lower viscosity means that the resin will flow into the details better and be less prone to hold bubbles. As far as the finished final resin goes however I am not sure as they do not discuss the cured resins shore hardness or flexibility so I will not be able to comment as to which would survive tabletop use better as some resins are extremely hard but brittle while others may be softer yet have a bit of give to them and are therefore less prone to breaking if dropped. You want to find a resin that has a low viscosity while pouring and strikes a good balance between hardness and flexibility.

One last thing. The dude in this video uses glue sticks instead of latex and silicone. Has anyone tried this

https://www.youtube.com/watch?v=SoMLvLuUlHc

Would latex be suitable for a 1-off resin casting? I've been looking for something that would be suitable for a 1-off 2 part mould.

Depends...

Latex - regular gooey, air cured latex - is a pretty poor mold making compound for doing small details more than once. It holds details well enough, but it is best suited for molds that are built up in layers because of how much it shrinks while curing as well as those which are reinforced because of how easily it tears.

Deep details are hard to reinforce and building up layers on something "miniature" can still end up having unacceptable levels of shrinkage. The "best" I have used shrank 5%, while many of them are 10% or higher. You can design around that issue - but 2 part compounds will prove to be much easier to work with (even though they are much more expensive).

For one off molds - I normally wont cast, just build it again. For a dozen or so though, I will use a vinyl mold compound (heat meltable and reusable) and generally cast them more simplified. Something like a human soldier would have all the important bits - but I won't try to capture the really fine details. Those get left off and sculpted on each one (or I will make a separate press mold for things that need to be uniform like canteens...or a different mold for more complex items...).

Not that latex doesn't have its uses for hobby casting. I will often use it to make big molds - stuff like the face of an interesting rock or whatever that I can't easily slice up and put on a game table. The shrinkage isn't very relevant when it doesn't have to match up with anything and I can build it up, reinforced with a roving mesh and use it a few dozen times (reserving the first pull as a master so I don't have to go back to find the rock again...).

Also works well enough as terrain itself. Stuff like Zuzzy Matts are made of latex, flexible - cheap - takes paint well enough.

Casting figures and little bits though, not worth the hassles for the saving IMO.

 Sean_OBrien wrote:

Casting figures and little bits though, not worth the hassles for the saving IMO.

He's from Romania though, they have a different time / money coefficient.

I know...even there though - I think I would probably look at sculpting one offs versus messing with trying to cast with a liquid latex mold.

Either that or look into spin casting. The mold blanks are cheap enough, can put together a setup fairly easily, and the vulcanized rubber is much more durable than air cured latex.

Many years ago when I was broke and otherwise limited in terms of my casting options - I messed around a bit with various things from liquid latex to air cured silicone caulk. Things like the caulk provide for better molds - though making the molds is a bit of a pain. Shrinkage is an issue though with any air cured materials though - as however much solvent is in them to keep em fluid evaporates, the remaining solids will shrink to make up the difference.