Support shell, clay wall problem.

Discussion in 'Sculpture and Makeup Effects' started by Vandark, Jul 28, 2015.

  1. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    hi there, I'm trying to build a wall across my silicone mould so that I can make a support shell in to halves.

    I just can't get the clay to adhere to the silicone, no matter how soft or melted I get it.

    does anybody have any tips or alternatives please?

    thank you!
     
  2. Sinned

    Sinned Well-Known Member

    Trophy Points:
    635
    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:

    supportshell1_zpslqcyr6pq.jpg supportshell2_zpsoxoutng4.jpg supportshell3_zpshxxvcbkm.jpg
    supportshell4_zpsy7bvmllj.jpg supportshell5_zpseq7ooia2.jpg
    supportshell6_zps7vosycbw.jpg
     
    Last edited: Jul 28, 2015
    Mr Mold Maker and zebracardeath like this.
  3. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    that's absolutely brilliant! but sadly, waaaaay beyond my abilities! haha!

    it's amazing how many ways things can be done with a bit of ingenuity.
     
  4. Sinned

    Sinned Well-Known Member

    Trophy Points:
    635
    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.
     
    Last edited by a moderator: Nov 8, 2018
  5. Mr Mold Maker

    Mr Mold Maker Sr Member

    Trophy Points:
    1,990
    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!
     
    Last edited by a moderator: Nov 8, 2018
  6. Sinned

    Sinned Well-Known Member

    Trophy Points:
    635
    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!
     
  7. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    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
     
  8. Sinned

    Sinned Well-Known Member

    Trophy Points:
    635
    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.
     
  9. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    Hi there,

    I've applied a plasti paste shell, but it's been 3 hours and it's still kinda rubbery....any ideas?
     
  10. andy19422

    andy19422 Well-Known Member

    Trophy Points:
    866
    sounds like you didn't mix it enough:(
     
  11. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    noooooooooooooo! I mixed it for ages, how long does it usually take to set?
     
  12. Sinned

    Sinned Well-Known Member

    Trophy Points:
    635
    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.
     
  13. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    it's actually suddenly hardened!!

    now the problem is, I can't get the * 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! *!
     
  14. Vandark

    Vandark Sr Member

    Trophy Points:
    1,095
    yup... was stuck fast... had to dremel in two.....

    managed to slice through the rubber... but should be OK...

    it's a nice thick mould and should hold steady in what's left of the support shell.
     

Share This Page