Molding sculpted arms in Ultra Cal 30?

Discussion in 'Sculpture and Makeup Effects' started by wholesomejoe, Jul 24, 2015.

  1. wholesomejoe

    wholesomejoe Active Member

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    I'm going to be molding a set of turtle arms I sculpted this weekend, along with a pair of legs.
    My question is, do I mold them on a stand/armature or do I take them off the armature and lay them flat?

    If I have to do it on the armature I will have to make a more sturdy stand because I don't think it can withstand the weight of the clay AND the Ultra Cal..

    Can anyone help?
     
  2. Mr Mold Maker

    Mr Mold Maker Sr Member

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    It is (most of the time) easier to mold a piece like an arm laying down. Fighting gravity is an uphill battle that I always try to avoid if it isn't neccesary to fight.
     
  3. wholesomejoe

    wholesomejoe Active Member

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    Can you elaborate? I've asked two other people, and the guy who is helping me mold said we had to do it with them standing up.
     
  4. Mr Mold Maker

    Mr Mold Maker Sr Member

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    Without pictures of the specific piece I can only speculate, but in general molding a piece vertically instead of horizontally (with stone) is not a good idea. As I said, you're fighting gravity. That means you're fighting the weight of the stone on the sculpture and stand, and constantly chashing the stone back up the mold. It is a good way to get thin spots and make a weak mold.

    If you lay the piece down on some towels or a "pillow" of clay you can use some wood or dry wall to build up to the sculpture, then make your dividing wall, and put the stone on top of the sculpture.

    Does that make sense? If you need me to reexplain anything I'd be happy to try.
     
  5. wholesomejoe

    wholesomejoe Active Member

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    Here's a photo.

    Thanks for the help!

    [​IMG]
     
  6. Mr Mold Maker

    Mr Mold Maker Sr Member

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    Lay them down palm up, make your dividing wall, (careful of undercuts! ) and mold. It looks like you can get away with a two piece no problem.

    There is actually no benefit at all to mold them vertically like that, and will cause you many more problems than its worth.
     
  7. wholesomejoe

    wholesomejoe Active Member

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    My friend is worried doing it that way will distort the sculpt with the weight of the utracal and burlap bandages.

    I'm also doing legs.. pictured here.. I've taken pictures since this one, so they are more detailed than this now. I have both legs to do.

    [​IMG]
     
  8. Mr Mold Maker

    Mr Mold Maker Sr Member

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    The legs would be more or less the same process. I'd probably recommend a three piece. Front of the leg and top of the foot, back of the leg, and then bottom of the foot.

    I have never in my time mold making professionally had a sculpture distort under stone. There is a little bit of science behind this, as far as I understand... When applying Ultracal you do a splash coat first. Also known as a "detail coat." Once this has kicked it has effectively made a shell of stone that will distribute the weight evenly across the sculpture as you apply subsequent layers.

    Laying horizontally the weight will be distributed evenly across the surface, but vertically you ask? All the weight will be pulling down, and that's where you run into issues.. I've heard horror stories of stone molds pulling clay right off of armatures and stands tipping over due to the weight imbalance.

    Ultimately it is your sculpture and your mold to make, and I wish you the best of luck in that process.
     
    Last edited: Jul 25, 2015
  9. wholesomejoe

    wholesomejoe Active Member

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    Looks like my helper isn't coming after all, so I am all alone in my venture... I need to get these molded.
     
  10. wholesomejoe

    wholesomejoe Active Member

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    Also, which is easier to use for a beginner.. ultra cal 30 or hydrocal?
     
  11. Mr Mold Maker

    Mr Mold Maker Sr Member

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    For a beginner I'd recommend ultracal just because it is more forgiving.

    Hydrocal takes more skill to use properly because you can't do it in layers like you do with Ultracal. Hydrocal expands as it sets, which will crack previous layers, so it requires very precise timing with one big batch. Ultracal doesn't, so you can do it layer by layer.
     
  12. wholesomejoe

    wholesomejoe Active Member

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    Thanks so much! You've been a big help, looks like I'll be putting it off another week while my local source gets restocked! I'm just glad I actually have a place where I can just buy this stuff locally.. it would cost so much more if I had to ship it.
     
  13. wholesomejoe

    wholesomejoe Active Member

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    Okay so for my arms, (and I'll leave you alone for a while...)

    I'm going to lay those down flat, palm up.. build up a dividing wall in white clay (the cheaper water based stuff), add in some keys for realignment... paint on a detail coat of ultracal, then a thicker layer, then a layer of burlap, maybe another layer of burlap, and then another layer of ultra cal, smooth it out.. let it set. Turn it over, remove the clay wall, cover the mold line with vaseline so that the ultracal doesn't stick to itself, repeat the same as the other side. Pry open, profit!

    The Wed clay seems to be pretty easy to damage unless you let it stay in the air quite some time. I still wind up nicking it. I wonder how you keep from damaging the sculpt with the dividing wall?

    Also for the legs, I've seen people do two piece molds, where it's the back and bottom, and the top of the foot and the front of the leg. I'm not sure how to go about that. I want to keep it as simple as possible with as minimal seam lines as possible.
     
  14. wholesomejoe

    wholesomejoe Active Member

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    I actually see what you mean now.. front, back, and bottom of the foot. My question would be, which part to do first? The back, and how do you seperate the dividing walls for each part of the foot?
     
  15. clonesix

    clonesix Sr Member

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    Am I late to this party?

    What are your model sculpted with? Water clay? Oil Clay?

    It depends how tough your sculpt is. If it has an armature in it, it will be strong enough to hold its own weight.

    I always coat my sculpts with several coats of clear to give it a good shell. Lay it down flat, well supported so that nothing is crushed. Mark your seam line at the outer most edge of the model with a felt marker. once the parting wall is formed, it helps support the weight of the gypsum. There should be no distortion to the model unless it is very soft water clay, and in that event, let the clay stiffen up as it loses moisture and it will be ready to go in 1 day.
     
  16. Mr Mold Maker

    Mr Mold Maker Sr Member

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    Sorry, I must have missed your reply.

    Clonesix is correct, seal the sculpture with Crystal Clear. One coat is all I use. If you use too many coats it will clog up your detail a little so just be aware of that.

    It's a good idea to apply a release over the sealer to facilitate cleaning later down the road, as well as removing the dividing wall cleanly. Frekote lifft is my go to for stone work, but Ultra 4 or Ease Release 200 may be more readily available to you. You can use these to release the stone halves from each other, or you can brush a thin layer of Vaseline. Heating the Vaseline gently with a hair dryer will help it get in all the nooks and crannies.

    I'd highly recommend Gary Ye's Stan Winston School tutorial on stone mold making. I believe they run a free seven day trial, so it's absolutely worth the watch.
     
  17. wholesomejoe

    wholesomejoe Active Member

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    One last question, how big of a mold can one make with one bag of Ultra cal 30?
     

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