Protecting Master when Moldmaking

Hey all, was curious if there's a widely accepted means of protecting your master when making a silicone mold? The specific project I have in mind involves a functional KWC Luger P08 airsoft pistol, and I'd hate to completely ruin it during the moldmaking process

Sorry if this is a simple question, did a little Google Fu earlier and came up with nothing on the subject (plus this will be my first resin casting project so I'm a bit nervous [emoji28])


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In my experience, silicone molds are pretty gentle to the masters. Your biggest issue would be keeping the silicone from flowing into all the gaps and mechanisms of the gun. I like to use a soft clay to fill those gaps and holes. You'll have to disassemble and clean your master no matter what after molding. If you can keep the silicone out, that will be easier.

I haven't heard if the silicone causes any chemical reactions to gun blueing or nickel finishes. Maybe someone else can answer that, but I've seldom found any issues with that myself.

Duncanator said:

In my experience, silicone molds are pretty gentle to the masters. Your biggest issue would be keeping the silicone from flowing into all the gaps and mechanisms of the gun. I like to use a soft clay to fill those gaps and holes. You'll have to disassemble and clean your master no matter what after molding. If you can keep the silicone out, that will be easier.

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Do you have any experience using liquid latex to seal said gaps? Obviously modeling clay would be easy to use in the barrel and for larger gaps, but I'm wondering if the latex would work better in smaller nooks and crannies


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I haven't tried liquid latex, but it might prove harder to clean off; especially if it dried and "glued" your gun together. I'm sure it would work well for sealing up the fine gaps, but I've had good success with oil clays for that too. The clay just wipes off. I roll a little snake of clay, press it into the seam, and the clean away the excess with a wooden stick.

Just another thought: If you are planning to vacuum de-gas your silicone, I would recommend doing it in a separate container and then pouring it into the gun mold. If you de-gas the silicone in the gun mold, you run the risk of the silicone getting sucked past the sealed seams into the inner workings of the gun and filling it with silicone.

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I hope I'm not scaring you off from making your mold. I just want to help folks avoid some of the mistakes I've found out the hard way.

Duncanator said:

I hope I'm not scaring you off from making your mold. I just want to help folks avoid some of the mistakes I've found out the hard way.

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Haha not at all. I've been dying to finally get into moldmaking so I really appreciate all the advice! Especially if it helps me avoid making mistakes my first time out



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Just fill any gaps with monster clay.

Latex will inhibit most silicones.. I'd definitely avoid that if I were you!

I really like Klean Klay for mold making. Reynolds has a version of it called Sculptex I believe. A block of soft should be enough to fill any gaps.. two or three would be enough for a wall. Monster Clay works too as JB mentioned.

IAmTheClayman said:

Do you have any experience using liquid latex to seal said gaps? Obviously modeling clay would be easy to use in the barrel and for larger gaps, but I'm wondering if the latex would work better in smaller nooks and crannies


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Don't use Latex anywhere near silicone!!
There is another option.... Usually you'd mix up your silicone without any thixo additive & either brush or pour it on. If you mix up a small amount with a thixo additive & with a small artists brush paint the silicone over the gaps to cover them. Once that's started to set then do your pour or your brush up.

the thixo mix should be a similar consistency to silicone caulking & doing this way may well save you a lot of clean up.

HTH

IAmTheClayman said:

involves a functional KWC Luger P08 airsoft pistol, and I'd hate to completely ruin it during the moldmaking process

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not a dumb question at all. one thing to be careful of is that as your master is a weapon of sorts, you most certainly do not want any small bits of silicone clay or whatnot or even a thin coat remaining anywhere in the barrel or in the mechanical interior. being only an air pistol, it wont backfire on you like a real pistol could, but even though the silicone itself wont damage it, fireing it with bits of silicone in it might damage the inside of the barrel.

Other than that, as the others mentioned, don't use latex, and avoid using clays with sulfur in them. Silicone does not like sulfur either.

I am not familiar with the master, but cant you just disassemble and just mold only the pieces you need and cast them?

I also use the same method that Leigh mentioned (without the additives) whenever I have a lot of fine detail, that will also give you a much better "bubble-free" mold.However I do not use a brush, if a brush hair falls out, it will quite likely ruin the mold. In my experience, you can even let the first coat completly cure before doing the next coat, silicone adhers to silicone quite well (as long as it is the same type). just make sure you do not get any contamination (dirt, debris, removal agents, etc) on it between the coats. In this way I very often recycle old molds by cutting them up into little pieces and dropping them into the fresh silicone as I pour it. but here also, make sure there isnt any removal agent from casting on the cut up pieces.

regarding removal agents, once you start casting from your mold, my favorite is talcum powder. it is easy to use and dirt cheap and you will never get any orange-peel effect as you can with the spray-on stuff.

opal1970 said:

I am not familiar with the master, but cant you just disassemble and just mold only the pieces you need and cast them?

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I don't necessarily need the resin replica to be able to be disassembled, so I wasn't planning on casting the air pistol in multiple sections, although I would probably block up the barrel and use clay or something else to fill larger holes.

opal1970 said:

I also use the same method that Leigh mentioned (without the additives) whenever I have a lot of fine detail, that will also give you a much better "bubble-free" mold.However I do not use a brush, if a brush hair falls out, it will quite likely ruin the mold. In my experience, you can even let the first coat completly cure before doing the next coat, silicone adhers to silicone quite well (as long as it is the same type). just make sure you do not get any contamination (dirt, debris, removal agents, etc) on it between the coats. In this way I very often recycle old molds by cutting them up into little pieces and dropping them into the fresh silicone as I pour it. but here also, make sure there isnt any removal agent from casting on the cut up pieces.

regarding removal agents, once you start casting from your mold, my favorite is talcum powder. it is easy to use and dirt cheap and you will never get any orange-peel effect as you can with the spray-on stuff.

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Will definitely keep this in mind, thank you guys for the tips!