So I've been trying to cast puppet heads from platinum cure silicone lately with limited success, mostly because it's easy to inhibit the cure and it can't really be painted after it's cured. I know foam latex is a common material for puppet casting, but I was at the art supply store and I saw this stuff: http://www.amazon.com/Smooth--Foam--Pourable-Flexible-Trial/dp/B00I...

Does anyone here have experience with urethane foam? I haven't found any examples of it used for stop motion puppets but it seems similar to foam latex. Also, does anyone know if it can be painted?

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There was a discussion about this a while back. I may try to fish it up if I can. But I'll offer my 2 cents.

I personally don't like using urethane foams for my puppets as I find even the very low density variants of it urethane tends to feel stiffer and almost drier than foam latex. Urethane doesn't stretch the same way that latex or silicone will. It can still be used but you will want to pay very close attention to densities or durometer (hardness of cured material) which Smooth-On denotes in pounds with their Flex-Foam lines by the number following the name. The larger the number the higher the density. You always want to pay close attention to the expansion ratios as well. When urethane cures it expands pretty aggressively. So heavy strapping around molds and careful measurements are needed to ensure the cast puppet doesn't blow out the mold at the seams, causing a distorted cast.

As for painting urethane, it is loads easier to do than painting most silicones (which isn't impossible by any stretch either if you use the right materials and methods). My only experience with urethane is casting stunt weapons and props for films, so I tend to not do a lot of highly detailed finish painting with it. Typically, you'll want to pigment the urethane prior to casting. That mostly helps limit the amount of paint that needs to be done post-cure. So as far as detailing your puppet after pulling a cast you can use PAX paint which is thinned acrylics mixed with pros-aide (a medical and cosmetic glue) or flexible acrylic enamels. Definitely avoid lacquer paints though! I tend to use Smooth-On's Brush-On 40 urethane rubber thinned with a tiny bit of mineral spirits and mixed with pigments or colorants.

The 2-part soft urethane foam is not that good, it bends and compresses but doesn't stretch much.  But yes, it can be painted easily with acrylic or acrylic/pros Aide mix.  Or you can build up onto it with liquid latex. I've used it to cast a body that is covered in clothing, it was skinny enough that not a lot of stretching was required.  I could have built it up with cut upholstery foam, which is really the same thing but does stretch better, but I already had the body mould so that was quick to do.  The head was silicone, and the hands were liquid latex built up over the wire.

I still cast some things in foam latex - large bulky puppets that would be too heavy if cast in silicone, or scaley wrinkly characters where the surface wrinkling you can get with foam latex is not a problem.  But for child characters with smooth skin, silicone is the best.  

I made a 1:6 scale horse, actually bought some urethane as one option for casting it, in case my latex was too old, but went with my foam latex instead.

Silicone can be painted with more silicone.  I add the Silc-Pig pigments to more of the same Platsil or Smooth-On Ecoflex 00-30 that I cast the puppet in.  But I have found that too much pigment can affect the cure.  I put pigment in the silicone that I use to paint the skin on the mould with, and fill it with, so it is already a good base colour.  

If you used a plasticine that contains sulphur to sculpt the head, then made a plaster mould of it, there can be a trace of it in the mould and the silicone will not cure.  If you use Monster Clay or Chavant NSP or any other that is sulphur free, that won't be a problem.  Also if you cast latex in the mould first, then decide to cast in silicone, that will inhibit the cure.  I did that, it stayed liquid in the mould forever! So then I did a lot of tests with a small amount of Platsil onto different clays and other materials, just to make sure I was not using anything that would stop it curing.  

Another thought I just had if you do end up going back to silicone is trying tin cure silicones. Although it's usually for mold making so very soft durometers aren't easy to find, several companies make soft tin cure silicones. In the 10A durometer range I believe. I know for sure BJB Enterprises and possibly Smooth-On produce several viable tin cure silicones, but, I'm sure there are others. It doesn't last quite as long as platinum cures would, tin cure tends to breakdown faster, but for a short film it should definitely last. And the benefit of tin cure vs platinum cure is that it is much less prone to cure inhibition. The same painting rules do apply to tin cure silicones as well.

Hmm, I've used the OOMOO tin silicones in the past for molds, but it cures a pretty vibrant purple, do you know of any way to color it/ other silicones that cure clear? Thanks for the tips.


Ethan Bartholomae said:

Another thought I just had if you do end up going back to silicone is trying tin cure silicones. Although it's usually for mold making so very soft durometers aren't easy to find, several companies make soft tin cure silicones. In the 10A durometer range I believe. I know for sure BJB Enterprises and possibly Smooth-On produce several viable tin cure silicones, but, I'm sure there are others. It doesn't last quite as long as platinum cures would, tin cure tends to breakdown faster, but for a short film it should definitely last. And the benefit of tin cure vs platinum cure is that it is much less prone to cure inhibition. The same painting rules do apply to tin cure silicones as well.

Yeah, based on yours and Ethan's advice I think I'll be trying to learn more about working with silicone, I tried a head cast with Dragon Skin and Silc-Pig last night, I'm hoping this one turns out. Thanks for the the response. 

StopmoNick said:

The 2-part soft urethane foam is not that good, it bends and compresses but doesn't stretch much.  But yes, it can be painted easily with acrylic or acrylic/pros Aide mix.  Or you can build up onto it with liquid latex. I've used it to cast a body that is covered in clothing, it was skinny enough that not a lot of stretching was required.  I could have built it up with cut upholstery foam, which is really the same thing but does stretch better, but I already had the body mould so that was quick to do.  The head was silicone, and the hands were liquid latex built up over the wire.

I still cast some things in foam latex - large bulky puppets that would be too heavy if cast in silicone, or scaley wrinkly characters where the surface wrinkling you can get with foam latex is not a problem.  But for child characters with smooth skin, silicone is the best.  

I made a 1:6 scale horse, actually bought some urethane as one option for casting it, in case my latex was too old, but went with my foam latex instead.

Silicone can be painted with more silicone.  I add the Silc-Pig pigments to more of the same Platsil or Smooth-On Ecoflex 00-30 that I cast the puppet in.  But I have found that too much pigment can affect the cure.  I put pigment in the silicone that I use to paint the skin on the mould with, and fill it with, so it is already a good base colour.  

If you used a plasticine that contains sulphur to sculpt the head, then made a plaster mould of it, there can be a trace of it in the mould and the silicone will not cure.  If you use Monster Clay or Chavant NSP or any other that is sulphur free, that won't be a problem.  Also if you cast latex in the mould first, then decide to cast in silicone, that will inhibit the cure.  I did that, it stayed liquid in the mould forever! So then I did a lot of tests with a small amount of Platsil onto different clays and other materials, just to make sure I was not using anything that would stop it curing.  

I definitely wouldn't advice Oomoo for puppets. It is too hard of a durometer and yeah the nice purple color isn't too nice to have to paint over :P
If you're trying the tin cure route, I'd recommend Smooth-On's Mold Max T, which is a water white translucent (the same as Dragon Skin) silicone and can be pigmented pre-casting and/or painted with a silicone paint mix post-cure. And if BJB offered more convenient trial sizes rather than basically 'lots', 'tons', and 'way too much' sizes then I'd highly recommend their TC-5005 A/B.

Of course, as I write this is only just now occurs to me that you mention casting puppet heads in particular, so 10A hardness tin cure silicones (which is the softest I've found readily available) might not be soft enough depending on the scale of your heads or what sort of demands you have on range of movement.

Hayden Setlik said:

Hmm, I've used the OOMOO tin silicones in the past for molds, but it cures a pretty vibrant purple, do you know of any way to color it/ other silicones that cure clear? Thanks for the tips.


Ethan Bartholomae said:

Another thought I just had if you do end up going back to silicone is trying tin cure silicones. Although it's usually for mold making so very soft durometers aren't easy to find, several companies make soft tin cure silicones. In the 10A durometer range I believe. I know for sure BJB Enterprises and possibly Smooth-On produce several viable tin cure silicones, but, I'm sure there are others. It doesn't last quite as long as platinum cures would, tin cure tends to breakdown faster, but for a short film it should definitely last. And the benefit of tin cure vs platinum cure is that it is much less prone to cure inhibition. The same painting rules do apply to tin cure silicones as well.

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