Support shell, clay wall problem.
- Thread starter Vandark
- Start date
Depending on what you're making your support shell out of, you can try a process I recently adopted, for multi-part shells, using Plasti-Paste. The same process may work with other materials, but I haven't tried it.
* Cut and tape index cards across your dividing line, to get a complete profile of the silicone.
* Careful of undercuts
* Transfer that profile to two pieces of 1/4" plywood, and cut them out with about a 2 or 3" margin.
* These are going to make the mating surface of your two shell halves.
* Sandwich them together, and drill holes for bolts, keeping them well above the profile edge, so you have room to work.
* I'll also sometimes drill little divots a little above the profile edge, to give the Plasti-Paste a little more surface area to bite into.
* Bolt the two halves together, and give the edges a quick sanding, if you wish.
* Keeping the halves bolted together, place it over your silicone mold, and then run a bead of hot glue along the edge. If you have any large gaps, they can be plugged with clay. Just make sure there aren't any spots where the paste can get underneath, and weld the two halves together!
Now you can make your shell, and do both halves at the same time. The Plasti-Paste should adhere to the wood very well, and once cured, you'll have a fool-proof mating surface for both halves.
For a more extreme version of this method, check out Volpin Props; he goes in to pretty good detail about multi-multi-part shells, somewhere on his blog.
Here are few pictures that probably explain a little better:
* Cut and tape index cards across your dividing line, to get a complete profile of the silicone.
* Careful of undercuts
* Transfer that profile to two pieces of 1/4" plywood, and cut them out with about a 2 or 3" margin.
* These are going to make the mating surface of your two shell halves.
* Sandwich them together, and drill holes for bolts, keeping them well above the profile edge, so you have room to work.
* I'll also sometimes drill little divots a little above the profile edge, to give the Plasti-Paste a little more surface area to bite into.
* Bolt the two halves together, and give the edges a quick sanding, if you wish.
* Keeping the halves bolted together, place it over your silicone mold, and then run a bead of hot glue along the edge. If you have any large gaps, they can be plugged with clay. Just make sure there aren't any spots where the paste can get underneath, and weld the two halves together!
Now you can make your shell, and do both halves at the same time. The Plasti-Paste should adhere to the wood very well, and once cured, you'll have a fool-proof mating surface for both halves.
For a more extreme version of this method, check out Volpin Props; he goes in to pretty good detail about multi-multi-part shells, somewhere on his blog.
Here are few pictures that probably explain a little better:
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Haha, it's actually pretty easy, but does call for some power tools. 
Back to the clay then, Mr Mold Maker mentioned, in a different thread, that problems could arise from the actual clay you're using. Slightly different context to that conversation, but thought it worth mentioning here. If you're doing the walls with WED, that could be the issue. Rather, try EM210 or EM700 (if you're not already). That stuff is awesome for mold work.
Back to the clay then, Mr Mold Maker mentioned, in a different thread, that problems could arise from the actual clay you're using. Slightly different context to that conversation, but thought it worth mentioning here. If you're doing the walls with WED, that could be the issue. Rather, try EM210 or EM700 (if you're not already). That stuff is awesome for mold work.
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Mr Mold Maker
Master Member
Shpeak of de devil... And he shall appeeear!
Sorry. Just watched The Dark Knight Rises for the first time in forever. :lol
Okay, down to business. Now you say that you can't get the clay to adhere to the silicone no matter how soft or melted you get it? Are you trying to use oil based clay to make the wall?
As Sinned mentioned in reference to another thread, the clay you are using may not be the best for the task at hand. Oil based clay simply by nature of being oily, doesn't want to stick to silicone. For now I'd cross that off the list in favor of a water based clay like EM210 or 700.
My next question is can the piece be layed down and a wall of clay be built up to the line of division instead of molding with a free standing wall? This way, the clay doesn't have to "stick" to the silicone, it just has to support it.
If for some reason it can't, you could try to clean the silicone with some 99% IPA and adhere a key running where you want to divide the wall, and lightly cut into the key to embed some shim. To make the key, we typically use aluminum trim channel you can find at any hard ware store, just close up the ends, pour your silicone, and you've got a perfect key. To adhere it, place down a line of fresh thickened silicone and use Bobby pins to tack the key down as the silicone cures. You can then use the thickend silicone to fill any gaps between the key and the rest of the mold.
Hope this helps or at least gives you an idea.
Sinned love the pumpkin orange plastipaste!
Sorry. Just watched The Dark Knight Rises for the first time in forever. :lol
Okay, down to business. Now you say that you can't get the clay to adhere to the silicone no matter how soft or melted you get it? Are you trying to use oil based clay to make the wall?
As Sinned mentioned in reference to another thread, the clay you are using may not be the best for the task at hand. Oil based clay simply by nature of being oily, doesn't want to stick to silicone. For now I'd cross that off the list in favor of a water based clay like EM210 or 700.
My next question is can the piece be layed down and a wall of clay be built up to the line of division instead of molding with a free standing wall? This way, the clay doesn't have to "stick" to the silicone, it just has to support it.
If for some reason it can't, you could try to clean the silicone with some 99% IPA and adhere a key running where you want to divide the wall, and lightly cut into the key to embed some shim. To make the key, we typically use aluminum trim channel you can find at any hard ware store, just close up the ends, pour your silicone, and you've got a perfect key. To adhere it, place down a line of fresh thickened silicone and use Bobby pins to tack the key down as the silicone cures. You can then use the thickend silicone to fill any gaps between the key and the rest of the mold.
Hope this helps or at least gives you an idea.
Sinned love the pumpkin orange plastipaste!
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Haha, I thought it was fitting, this being the mold for Twisty. I got bored with the standard paste color, so have taken to throwing in some tint, just to keep things interesting.
Sweet tip on the dividing key, for embedding shims!
Vandark
Sr Member
Shpeak of de devil... And he shall appeeear!
Sorry. Just watched The Dark Knight Rises for the first time in forever. :lol
Okay, down to business. Now you say that you can't get the clay to adhere to the silicone no matter how soft or melted you get it? Are you trying to use oil based clay to make the wall?
As Sinned mentioned in reference to another thread, the clay you are using may not be the best for the task at hand. Oil based clay simply by nature of being oily, doesn't want to stick to silicone. For now I'd cross that off the list in favor of a water based clay like EM210 or 700.
My next question is can the piece be layed down and a wall of clay be built up to the line of division instead of molding with a free standing wall? This way, the clay doesn't have to "stick" to the silicone, it just has to support it.
If for some reason it can't, you could try to clean the silicone with some 99% IPA and adhere a key running where you want to divide the wall, and lightly cut into the key to embed some shim. To make the key, we typically use aluminum trim channel you can find at any hard ware store, just close up the ends, pour your silicone, and you've got a perfect key. To adhere it, place down a line of fresh thickened silicone and use Bobby pins to tack the key down as the silicone cures. You can then use the thickend silicone to fill any gaps between the key and the rest of the mold.
Hope this helps or at least gives you an idea.
@Sinned love the pumpkin orange plastipaste!
Thanks for your advice. First thing I need to do is get hold of some of the clay you mention!
Can anybody tell me if Plasti-Paste shells have any give in them. ie can I force the Shell off the rubber mould? or will it just crack?
thanks
Definitely NO give to Plasti-Paste; that stuff is solid. But it is also somewhat brittle, and it'll definitely crack, if you wrench it the wrong way, so you need to be careful with undercuts, and make sure they are all filled in well (thickened silicone), or accommodated for by a 2+ part shell. So long as you take care of that, you won't have any problems. It can still be a little hard to remove initially, since the clay underneath doesn't give much, but if you work it up gradually from all sides, it should come off cleanly. It's a good idea to wax up the silicone, prior to laying down the shell, which will help a little. I use smooth-on's Sonite Wax, but I'm sure there are other options.
Vandark
Sr Member
Hi there,
I've applied a plasti paste shell, but it's been 3 hours and it's still kinda rubbery....any ideas?
Vandark
Sr Member
sounds like you didn't mix it enough
noooooooooooooo! I mixed it for ages, how long does it usually take to set?
I don't recall what the full cure time is on it, but I always leave it overnight. If it's still not hardened up in the morning, that would indicate a problem, and you'd likely have to start over. Smooth-on has pretty good tech support if you contact them. Unless the product is really old, or the mix ratio wasn't right, it will set up. I've had small soft spots before from not mixing well enough, but never over the whole thing. I believe the thickness of application can also affect cure time. Thicker spots will heat up more, and cure faster, I think.
Vandark
Sr Member
it's actually suddenly hardened!!
now the problem is, I can't get the Damn mould out of the shell, it's stuck fast and I'm afraid of ripping the mould!
knew I should have done a 2 piece! Damn!
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