Major General Ariel Sharon 1973
Posted 18 May 2012 - 05:37 PM
That looks like a delicious dessert.
A delicious desert that makes your eyes itch.
Everything's cool with the mold in terms of surface bubbles.
It's the casting that's hard. Pictured the casts in order from right to left. The left most coming out the "best". I keep getting air trapped in particular places.
Lessons learned: Every bit needs a channel for material to come in an for air to come out(which isn't so easy to carve out of the mold). I'm seriously considering removing arms and such to have their own personal space. Make the registrations much larger for better fit. Make the main hole where I pour the polyurethane taller so it can push against the material in the lower parts. Mainly the part about air flowing out. We'll see what happens with the next experiment.
I lost the lens I made for the V5's and then found it (it's 1mm in diameter) on the floor among three beetles having a sex party. I then proceeded to lose it again. Decided to sculpt the lens in.
The canteen cap was too tall so I filed it down. Drilled a hole through the back of the canteen and joined it with the main figure. Also posed and somewhat fixed the left hand. The right is waiting for the binoculars.
His face looks the worst from this angle. I need to fix it somehow.
From this side everything seems on track.
Posted 19 May 2012 - 06:31 PM
Made the V.5 body.
Added left hand and some shape and strengthening of the right hand as well as the canteen cap. Gave the left side of the face some caresses with a sharp knife. Now the pistol holster looks really thin, I'll need to re-do it.
"everybody go there!"
"wait a minute, that way!"
Posted 20 May 2012 - 11:16 AM
After a bit of "research" I discovered the secret ingredient for casting without bubbles.
Actually, it's only a third of the solution for getting nice casts. The other parts are: degassing your Silicone in a vacuum chamber and putting the mold in a pressure chamber when you cast the "resin".
When you put talc powder on the mold it acts like Mentos in a coke bottle - it provides nucleation sites for the gasses and the air forms a bubble and floats inside the cast upwards. This gives a nice almost bubble free cast:
The only problem is if you get a big bubble near the surface you can see through it and like in this cast it can also cause the structure to fail. There's no bubbles on the surface but the leg snapped off because it was mostly an air bubble with a thin wall of material. I glued it.
This is where you need the second part of the equation: Pressure chamber. Unfortunately, these are very expensive so we won't be getting one any time soon but the idea behind it is that you place the still "wet" resin in the mold in the chamber and the increased atmospheric pressure causes the bubbles to shrink and diffuse into the material; like not enough hot air in a baloon! Also possibly it causes the resin to press into the mold making better crisper details. What this means is if you have also air pockets in your actual mold there, they will also shrink and cause, probably for the surface of the cast to be "pimply". That's why you need also a vacuum chamber to de-gas the silicone!!!!
Talc powder is a cheap and effective solution to bubbles on the surface of the cast- but it's not perfect.
Vacuum chamber you need for to de-gas your silicone. This is something you can possibly make.
Pressure chamber you need to compress air bubbles and push the resin into the surface of the mold making good, no bubbles cast. If you try to make one there's a good chance you'll kill yourself. You have to buy it. It's expensive.
Dentists use pressure chambers like this for the exact same purpose. I'll see if anybody maybe knows a friend who has a friend etc. etc. or we'll simply have to wait until imperfect casts somehow pay for making better ones.
A nice link about the casting process: http://www.militarym...icle.asp?a=5460
Posted 21 May 2012 - 07:26 AM
Posted 21 May 2012 - 11:20 AM
That's a large update. Good to see the general coming along and your casting improving. Ed Fortae over at Troll Forged knows a lot about casting resin. He might be a good source of information if you havent already talked to him.
Thanks for the tip, I'll look into it!
Two sessions today.
Holster buffed up.
Right arm mass.
Watch and sleeve (needs some more mass on the rear). Mass on left arm.
Posted 24 May 2012 - 04:27 PM
I forgot about 15mm Ariel. Keep going!
I've been busy making a portfolio website and setting up a blog for posting random things.
Here is the update on 15mm Arik. Added canteen, posed arms, basic structure fixing and connected the binocular slice I had made beforehand. The front slice,by the way, is much too big so on the next session I'll just make the lenses on the sculpt itself.
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