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Making a mold for casting silicone heads? Project start.

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rubherkitty
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Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

So, what do the pro's use? Fiberglass or silicone?
Tooling Gel coated fiberglass molds will offer a much longer life than silicone, but does not transfer detail as well.

Here's my plan for making a quantity of heads.

1. Starting w/a vinyl mannequin head, I'm making a 2-pc mold of that using Rondo.
Rondo is Auto body Bondo thinned w/ Polyester resin. This makes it much easier to smooth onto the head. The Rondo will be topped w/ 2 layers of fiberglass cloth & resin for strength.

2. The mannequin head I'm using is well shaped and the size I want, but not extremely detailed or the exact sculpt I want. 99% of MQ heads are closed mouth like this one and I want a open mouth. Therefore this initial mold will be used to cast a head out of clay over a work table armature so I can do sculpting work on the clay head and make provisions for the head being a doll head. Neck attachment design, removable eyes, etc.
The whole reason to do these steps is to save time of trying to design a head from scratch. I can always use this primary mold to cast more base model heads in the future for making other designs.

3. Now that we have a clay head of the final design, I will make a silicone mold of that.

4. I will then cast a one off plastic resin head in the silicone mold so I have a permanent pattern of the clay head sculpt.

5. I can then cast silicone heads in the silicone mold until it wears out.

6. If I still have the clay head, I can make another silicone mold based off that or can use the plastic resin copy.

7. I may also be able to make a fiberglass mold from the plastic resin head.

The issue w/ making a fiberglass & resin mold off of a clay sculpt is clay melts in heat and polyester resin creates heat when it cures which can screw up detail work.

Thoughts?
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Re: Making a mold for casting silicone heads? Project start.

Post by SculptorGuy »

I used to work with someone who cast with Rondo - and it shrinks quite a lot compared to other resins. At least that is what happened when we cast a small (but thick) 14 inch statue using it. It shrunk a good 10% on us.

Also you can cast silicone in silicone, but if there is even a small area where you don't have mold release - the mold and cast can bond together. I watched a video on a mold release you can pour into molds which is the recommended way to do it. That's because in places like ears and little undercuts, spray releases don't always work well. It was on the bity mold supply YouTube channel if I remember.

That said, I don't know about the toxicity of mold releases. That might be something you consider depending on your planned use for the head.
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Re: Making a mold for casting silicone heads? Project start.

Post by matt gloss »

Hi RK,just the thread I needed.... :D
Matt

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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

Thanks

The Rondo shrinkage might be based on how much resin was used? I only use about 30% resin and have mainly cast small items or made thin molds. But yeah, I would recommend using quality casting resins for making an actual finished part.

I have done some casting silicone in silicone and it's a nice system, but as you mention, make sure you apply the release property. I use spray release, but use a small modeling brush to paint in holes if need be.

Toxicity? Can't be much worse than me messing w/ polyester resin in my camper tonight! :drinking:
One of my missing bits of info is how to remove release from a finished product. I have been using alcohol which I know won't hurt silicone. Been using it on poly resin and bondo too, but try to just give it a quick wipe.

When casting silicone doll bodies, they suspend the skeleton inside the mold using wires and long screws. I assume when the body is pulled, they wipe it down w/ alcohol, pull the wires and seal over the holes where the screws and wires where. I know they seal the holes as these small dots have been discussed before. Not sure about the finishing process though. Abyss has quite a ordeal of washing the bodies down, trimming flash and they do some air brushing too.
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Re: Making a mold for casting silicone heads? Project start.

Post by Sodium »

We need more topics like this. The way I see it, the more people trying to make dollies, the greater the chances that we will hit that next big breakthrough in doll making. Imagine a world where a solution for durable, articulated fingers is found! o.0

~Sodium
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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

Sodium wrote:We need more topics like this. The way I see it, the more people trying to make dollies, the greater the chances that we will hit that next big breakthrough in doll making. Imagine a world where a solution for durable, articulated fingers is found! o.0

~Sodium
I have done some pretty in depth thinking about articulated hands and think they can be made well w/out poke throughs. They will just add more cost. But I don't plan on making cheap dolls, in quality anyway.

I'll probably just make non wired hands of firm silicone in a natural pose to start out.
They won't easily be damaged, but won't be rubber noodles either like wireless TPE doll hands.
Deal with more complex hands later.
Abyss offers the Duracast hands and that idea was discussed on here long before they started offering that. We had discussed making access plugs in the mold near the wrist where firmer silicone could be squirted into the hands w/a large hole syringe. :wink:

Here's where I'm at on the mold from the mannequin head.
Did all the blocking, clay work and Rondo last night.
Just finished the fiberglass coat tonight.
Here you can see I have to still cover the forehead area w/ fiberglass cloth and resin.
Next will be to flip it over and do the back side.
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Re: Making a mold for casting silicone heads? Project start.

Post by matt gloss »

Hi Rk super sculpey can be baked in a normal oven to harden,would this help with the heat issue?

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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

matt gloss wrote:Hi Rk super sculpey can be baked in a normal oven to harden,would this help with the heat issue?
That's a good idea, but...

I just did some research and my only problem is the clay head when prepared for molding will have polyester/ Bondo eyes installed w/ 1/4" bolt shanks sticking out. The eyes will also have been painted w/ primer, paint and gloss sealer. The head core may be plastic or wood attached to the steel pipe armature.
Basically more variables than just the S Sculpey material.

SS says: Bake at 275 °F (130 °C) for 15 minutes per 1/4 in (6 mm) thickness.

Polymer clay is PVC powder mixed with plasticizer and some other stuff (fillers, binders, pigment, etc). And as the heat in the oven rises, the PVC particles swell up a bit and soften, eventually fusing into a solid mass that we know as cured polymer clay. You need to bake the clay long enough and hot enough for this fusion to occur AND for those particles to fully fuse together to form a solid mass. If you bake at a lower temp, the particles don’t soften enough to fuse well. Also, if you bake for too short of a time, and the particles won’t have time to fuse well. You need both time and temperature.

I can still keep SS in my tool bag just in case though.
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Making the head mold will be a rather complex thing VS a simple 2 halve shell mold for a solid sculpture.
The mold shell will probably be 3 pcs and there will be and least 4 interior mold parts attached to the shell mold. Plus there will also be a plastic or fiberglass core form inside attached to the neck mount when the actual head is cast.
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Re: Making a mold for casting silicone heads? Project start.

Post by Siliconeman »

I would have the following workflow:

1. Starting with mannequin head make a silicone mould covering the head

2. Cast your modelling clay inside silicone mould, finalize the clay model sculpt and insert eyes which you will be using. Put parting line to head for 2-part mould separation.

3. Cast good quality gypsum over clay model, re-enforce with medical plaster with cloth.

4. Separate gypsum mould, clay model will most propably be destroyed. Clean the gypsum mould

5. You can now use your imagination whether to cast full silicone or build soft or hard centre part for the head.


Some comments on your plan

Separating hard mould from hard plug may be demanding. If the mannequin head is vinyl I presume it has some flex in it and in that case mould separation is easier.

Polyester resin is just awful material which shrinks when it cures and it does not keep its shape. Polyester tends to twist and turn in final form.

As SculptorGuy already mentioned it is demanding to cast silicone to silicone. Silicone does like to stick to another silicone - sometimes so hard that two silicone layers form one uniform silicone piece and you may end up destroying your silicone mould.

Hope you have a good vacuum chamber and vacuum pump

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Re: Making a mold for casting silicone heads? Project start.

Post by matt gloss »

8O
I think I may end up buying a head for the fabric doll I am making,I would really like a go at this one day when funds permit wastage in learning these skills :whistle:
subscribed 8)
cheers

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Re: Making a mold for casting silicone heads? Project start.

Post by SculptorGuy »

I haven't examined how these doll makers make hands but I do have one suggestion. If you use wire you can make the bones out of pro-poxy. It's a two part epoxy putty that is sort of like clay. You mix the two colors it has together (make sure to wear gloves and wet it so it doesn't stick to you) and then it hardens like steel. That's not exactly true, but that's how they advertise it. It is more like a semi-flexible (but barely) material. If you envision a cross between a very dense rubber and plaster, that's about how it behaves. Here's a link to some:

https://www.amazon.com/Hercules-25515-P ... 9802&psc=1

They use this method in stop motion puppets to make wire armatures. It is just a way to allow the bending of the parts to bend where you want and not like wet noodles. The wider the gap between bones, the longer the wire will last. The closer and the more acute angle bends means the wire can snap over repeated use sooner.
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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

Siliconeman wrote:I would have the following workflow:

1. Starting with mannequin head make a silicone mould covering the head

2. Cast your modelling clay inside silicone mould, finalize the clay model sculpt and insert eyes which you will be using. Put parting line to head for 2-part mould separation.

3. Cast good quality gypsum over clay model, re-enforce with medical plaster with cloth.

4. Separate gypsum mould, clay model will most propably be destroyed. Clean the gypsum mould

5. You can now use your imagination whether to cast full silicone or build soft or hard centre part for the head.


Some comments on your plan

Separating hard mould from hard plug may be demanding. If the mannequin head is vinyl I presume it has some flex in it and in that case mould separation is easier.

Polyester resin is just awful material which shrinks when it cures and it does not keep its shape. Polyester tends to twist and turn in final form.

As SculptorGuy already mentioned it is demanding to cast silicone to silicone. Silicone does like to stick to another silicone - sometimes so hard that two silicone layers form one uniform silicone piece and you may end up destroying your silicone mould.

Hope you have a good vacuum chamber and vacuum pump
Thanks Siliconeman

Hopefully I can get the fiberglass mold off the mannequin head. I did a test area and it came off fine. I used a good release agent. I also smoothed the ear contours over w/ clay as I will be re-sculpting them anyway.

The reason I used polyester is it's cheap and I already have plenty of it. Material cost might be $12.00 whereas silicone + mothermold material might run $40.00+. And the final result of the clay model for sculpting does not have to be perfect. I may just warm the clay and press into mold halves then mash them together over a ball on pipe armature. Put it outside in the cold weather to cool then pull the mold off. We'll see how it goes.

RE: Gypsum mold. I see where they cast gypsum in silicone molds, but can't find any info on casting silicone in gypsum. No reason that would not work though.
Not sure of how many castings you could get or how much detail there is with this system.
I plan to market the heads so want to get as many pulls from the mold as possible.

I will also really need a hard, but crack resistant out shell on the mold as I may have as many as 7 bolts or studs going in or out of the mold to hold internal forms such as eyes, oral mouth tunnel, speaker hole, etc.

I have the materials to build a degassing chamber that can handle a 8 gallon bucket.
Just need to buy the pump, hoses, valves, etc.
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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

matt gloss wrote:8O
I think I may end up buying a head for the fabric doll I am making,I would really like a go at this one day when funds permit wastage in learning these skills :whistle:
subscribed 8)
cheers
Are you looking for a silicone head?
I'm using a vinyl mannequin head on my plastic doll now, but she's not much fun to kiss. :lol:

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Thanks Sculptorguy. Neat stuff.
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Re: Making a mold for casting silicone heads? Project start.

Post by matt gloss »

Hi RK yes if I can afford,I have already 75% scuplted a head from sculpey clay a little bit more work on her she will be nice.
I will stick a pic up later just got a better camera :D
Thanks for the contributions peeps
Matt

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Re: Making a mold for casting silicone heads? Project start.

Post by rubherkitty »

Thanks Matt.
Maybe through this thread you can find a way to make the head on a budget.
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