How to fix pits in mold surface? HELP!

Discussion in 'Predator Anatomy (Costumes)' started by Khajaa, May 10, 2010.

  1. Khajaa

    Khajaa Unblooded

    First of all, I am a complete novice at this. I made an UltraCal 30 open mold of a cat nose I had sculpted, and I am using it to make prosthetics in latex. This worked well and good until I started making the casts. Apparently, there are pits in my mold, which are seeming to get bigger and bigger with every pull, causing my casts to have tiny bumps on them that are getting bigger every time.

    I searched the internet for an HOUR trying to find a suggestion on how to fill these holes, but I kept getting results on "mold" the lifeform and instructions on how to fix molds that are for fiberglass and metal...

    I turn to my fellow hunters in desperation - I know there are a lot of sculptors/casters here! Unfortunately, my sculpt was destroyed when I made the mold, so I really would like an alternative to re-sculpting the entire thing over! I thought perhaps using sealer would fix the pits... but that would destroy the mold's porous nature. I really am at a loss here. Would a kind mold release help? If so, what do you suggest? Should I mix up a little UltraCal to brush over the pits and hopefully fill them in?

    Please help if you can. I am making this for a commission due in a week and I don't have time to redo the sculpt. :)
  2. MasterAnubis

    MasterAnubis Elite Hunter

    I have tried two different things with a plaster mold. The first thing I tried was filling the pinholes with the clay I used on the sculpt. This worked for at least one pull and did fill the holes. The clay worked fine with the brush in latex I used. I would't know how well this would work in a slip cast.

    The other was fill the pineholes with another mix of plaster like your thinking. I had mixed results with that attempt and I can't tell you either way if it will work with Ultracal.

    Sorry if this doesn't help, it's what I've done though. Hopefully some one will chime in with some better experience.
  3. Khajaa

    Khajaa Unblooded

    Thank you for your ideas. I really am glad to have the support.

    I have also FINALLY found some stuff online at but I wonder if anyone else on here could give me an endorsement on these. I am most tempted to try #3.

    1) "I used plumber's epoxy putty to fill large holes and crack in my ultracal molds. Just use some Vicks Vap-o-rub to smooth it. Can't think of any reason why that wouldn't work."

    2) "we have had good success with fixing holes, cracks and even sometimes "resculpting" texture, detail and even sections within in a mold. The key we found is to always wet down the mold, really wet it down. If you apply plaster to plaster without wetting it, we found that many times the new areas will flake, break off. By wetting it, it creates a bondable surface. We have been able to go in and sculpt sections that have broken off. So try wetting down the mold, fill the cracks, smooth out with wet paper towels, and let dry. Sometimes, much the same way you patch drywall, you have to make the crack slightly bigger to fix. If you need to reconnect pieces of a mold, strap the mold together and repair from the outside first (so, you're adding more layers to the outside). When that sets up, go back to the inside and fix any surface issues."

    3) "I have been doing life-casts for awhile now and other molds made of Ultra-Cal 30 and I have tried just about everything there is to fix/repair holes and damaged areas. The one thing that I found to work great was joint compound (aka; wall board compound, sheetrock mudd, etc.). You can find it at any hardware store such as home depot or Lowe's. Look in the sheetrock section (sometimes it can be found in the paint section). The nice thing about using joint compound is that it is easy to smooth, doesn't set up suddenly (as opposed to trying to patch holes using a small batch of Ultra-Cal 30), is easy to sand and thereby shape (try doing that with Ultra-Cal 30 after it has set up). I have found that if you use 220 grit, extra-fine sandpaper not only can you sand/shape it the way you want, but it doesn't leave any marks from the sandpaper. Oh, and the reason why joint compound works so well is that, like Ultra-Cal 30 (or hydracal) it is gypsum based. So it is the perfect material to patch it with."

    4) "There is a material called Acryl 60 that you can use to mix up a batch of ultracal or hydrocal that acts as a glue to help the new material bond to the old. You should still wet down your mold before adding the new patches. With fine cracks, mix a thin batch of Ultracal with pure Acryl 60 no water, and force it into the cracks with a brush little by little. After trying a multitude of repair techniques, this is my favorite."

Share This Page