Tom is learning casting

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thd9791

Master Member
RPF PREMIUM MEMBER
Hi everyone
I’m learning something new during the pandemic. Now, I bought a whole kit last year, only made a huge mold for 4 small pieces and did one pull that wasn’t properly mixed and put it away. This year the silicone hardened and I don’t have much time left to use the resin before it goes bad... so I’ve been hitting the ground running.

and yes, I bought normal silicone but the beige mineral filled high impact resin... because all these lightsabers and blasters are beige. I didn’t get clay... starting off with 1 part molds first.. so basically hot glue

I bought new silicone, made new molds (thought I was being clever doing it in Tupperware until I couldn’t get at the sides of the molds like when I used Legos first) and P³ PoopaPapaPalps suggested I use cornstarch instead of baby powder

now, I also have been a lurker here a long time and fully understand recasting and it’s ramifications - all of these are found parts... switches knobs and model kit parts. There is an alternate mystery chunk in there and heck I even checked with the guy I bought it from if he felt weird about it just in case

I have also been using the vent from the oven or a heat gun to pop bubbles. I accidentally cooked my last pulls and they scalded and puffed up in the molds! Weeirddd

anyway, I wanted to share my journey, I love the idea of casting up found parts for props like set decorators and prop makers did on Star Wars...
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You can even see machining marks in the knobs!!! This is from a Saturn Michell Turntable
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Thanks for reading! I’ll continue my updates here. The Unimax switch is hard to get out and pops every time I extract a cast. It’s missing most of the full holes but the dimples are there to drill out
 

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PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
Baby powder is just starch with perfume added. Doesn't really matter which you use, just a light dusting will help pull the material when you pour it. I use talcum powder just because I have it readily available.

Depending on how fast your resin cures, you can do a beauty coat (a thin coat first) and slush that around and poke around tight areas and corners to make sure the resin fills it in. Once that cures, you pour in the rest.
 

thd9791

Master Member
RPF PREMIUM MEMBER
Baby powder is just starch with perfume added. Doesn't really matter which you use, just a light dusting will help pull the material when you pour it. I use talcum powder just because I have it readily available.

Depending on how fast your resin cures, you can do a beauty coat (a thin coat first) and slush that around and poke around tight areas and corners to make sure the resin fills it in. Once that cures, you pour in the rest.
son of a gun.. no wonder they act alike, almost sticky the powder is so small

This stuff is like thin cake batter right off the bat and starts to skin over within a few minutes. I couldn't have picked a harder resin to work with
 

PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
If that becomes too much of a hassle to play with, there's a bunch of neutral colored resins out there that can be tinted with pigments.
 

swgeek

Sr Member
If you leave the parts in the mold and sand off the flashing with an electric/pneumatic sander, it's easier than pulling them and then sanding them flat.

I use foam core for most of my mold boxes. Also you can use upside down deli cups. Hot glue them over the parts you want to mold and then cut the bottom out.
 

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thd9791

Master Member
RPF PREMIUM MEMBER
This is great thank you - I'll describe what I've been doing already

I wash the molds with a droplet of dish soap and water, and suck out all the droplets leftover with paper towels. Once they're dry I dust them with cornstarch, tapping the molds like a brownie tin until the surface is lightly dusted and uniform.

I use my girlfriend's trick of mixing the epoxy resin like she mixes ink in screenprinting shops, zeroing out the scale for each measurement we calculate so I don't lose material between cups. This heavy-duty resin is a 5:1 ratio, ...really

I put the molds on the floor and pour and bend my paper cup/bowl to make a spout. I get down on one knee and pour a REALLY thin stream and hit all the nooks and crannies first. for the pistons I pour from one corner, filling the mold. For the knobs I start in the center, that has really worked well for the cross knob.

The couple bubbles I still get every time seem to be around the rings of the piston holes and the motor coil plate holes... and very fine knurling seem to leave pinholes in the bumps but that could be a viscosity thing
 

thd9791

Master Member
RPF PREMIUM MEMBER
If you leave the parts in the mold and sand off the flashing with an electric/pneumatic sander, it's easier than pulling them and then sanding them flat.

I use foam core for most of my mold boxes. Also you can use upside down deli cups. Hot glue them over the parts you want to mold and then cut the bottom out.
Great idea on the sanding! Trying to picture this.. Do you mean you glue the cup upside down on a piece of foam core like a cage around the item (cutting off the bottom of the cup to open the top of the cage) or do you glue the items down in the cup, and just cut off the rim so it's not a tall cup?
 

swgeek

Sr Member
The former. Glue your parts down to a piece of foamcore, place the cup upside down over your parts glue it to the foam core (I usually use hot glue) then cut open the bottom. I find it's best to cut the bottom out instead of cutting the whole bottom off, if that makes sense. Also, when you're done you can use alchohol to break the hot glue free.
 

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thd9791

Master Member
RPF PREMIUM MEMBER
Welp, since i didnt have any deli cups I went with the same idea for a larger greeblie and whatever I had laying around!

Here goes nothing..
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Also doing another run of my other molds at the same time. This time I stopped pouring sooner, bent the molds to open up tight areas and I turned my heat gun on high.. basicslly flashed them for 5-6 seconds and a whole bunch more bubbles came up at once!

Didnt get a pic of that I was so focused.. but heres a shot of me mixing. The digital scale I keep off to the side - this is around 1.6 oz of resin and whatever 1/5 of that is of hardener.. .374 or something
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thd9791

Master Member
RPF PREMIUM MEMBER
Did a casual silicone pour - not sure if I want to do it again because there are pinprick holes in some corners... can you do the heat thing with silicone too?
 

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PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
Sure, depending on what you have. However, because of its viscosity, you're not gonna get them all in one go; the bubbles have to slowly make their way to the surface as it cures.

For really super-clean results every time, you'll need a vacuum chamber to get the bubbles out the silicone and then a pressure chamber to get the bubbles out of the resin when you cast your items.

It all ends up being an investment but that's a sure fire way to get it great every time. I don't even have a pressure chamber or a vacuum pot if that means anything. You're casts are already pretty good as it is now. Especially for Star Wars. You know very well what ugly pieces they used. :lol:
 

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