What is the best alternative to Ultracal 30 for making Silicone prosthetics?


I will be making my first full face silicone prosthetic and have been able to successfully lifecast my model however I can't get my hands on Ultracal 30 in Dubai, and am desperately looking for an alternative!! 

I have found an online medical supplies centre which stocks dental stone but I don't know whether that is a good alternative! 

This is the MSDS of the dental stone that I would be able to get out here:

Can anyone give me advice on what to look out for? 
I have so far gathered that my stone should be as smooth as possible and NON-porous if I want to work with silicone, and in the "Character Makeup Sculpture breakdown and moldmaking part one", Bruce Spaulding Fuller Talks about layering epoxical! But I haven't even been able to find Ultracal 30 here  :s !! 

If anyone has any advice on what I could use to substitute Ultracal 30 and epoxical please please let me know!! 
Any help is appreciated!! 

Thank you in advance!! 
Sonja  <3


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    Hi Sonja,

    Dental stone should work fine.  It's often mixed into the detail or print coat in stone molds to add a bit of strength and a smoother surface.  It's just more expensive than Ultracal, and lacks a few additives.

    Ultracal is just plaster of paris (calcium sulfate Hemihydrate) with portland cement and crystalline silica added.

    Dental Stone is is also calcium sulfate Hemihydrate, but it is created at a higher temperature and under pressure.  This makes it less porous and a bit harder.  (thus more expensive)  Dental stone lacks the portland cement and silica additives found in Ultracal.

    So in short, you should have good luck with any gypsum based molding material, bet it dental stone, plaster of paris, or a composite like ultracal/hydrocal/etc.  They are all quite similar, with the differences mainly being in hardness and porosity.

    The key to working with stone molds is knowing what the materials actually are (beyond the brand names) so you can adjust the mixtures as needed or find alternatives.

    Here are some of the more common formulas:

    PRODUCT(S): Ultracal‚ 30 Gypsum Cement 
    CHEMICAL FAMILY: Mixture of Calcium Sulfate Hemihydrate
    Plaster of Paris >85%
    Portland Cement <10%
    Crystalline Silica <5%

    PRODUCT(S): USG‚ Hydrocal White Gypsum Cement 
    CHEMICAL FAMILY: Calcium Sulfate Hemihydrate
    Plaster of Paris >95 %
    Crystalline Silica <5% 

    PRODUCT(S): Duracal
    Plaster of Paris >50% 
    Portland Cement >40%
    Crystalline Silica <5%

    PRODUCT(S): Hydrostone
    Plaster of Paris >90 %
    Portland Cement <5%
    Crystalline Silica <5%

    Another alternative is to use epoxy molds, which is the current industry standard for casting silicone.  Though the materials are much more expensive, and might be more difficult for you to obtain.

    And then there is fiberglass resin molds.  The material for these may be more readily available as they are used by many industries worldwide, but they can be a bit difficult to work with.  You need to wear a respirator for the resins and protective clothing/eye ware/mask for the fiberglass.

    Hop that helps!

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    Hi Chris!

    Thank you so much for your quick and thorough reply!!! It definitely helped me a lot! 

    I am now looking to order a type 4 dental stone from the local dental supplies with a compressive strength of Mpa 117 and make my molds using that, I figured using the hardest stone I could find would help make my molds last! 

    However I do have another question: about floating sculpts! (Should i post this in a different section?)
    My Lifecast is unfortunately made of Plaster of paris, and I was wondering whether it is still possible to float my sculpture off of it once i'm done. I am assuming it would be but I just wanted to check whether anyone has tried that before and run into any problems!

    Also about the separating agent:
    The only available separating agent I have found so far is Divosep by Vertex, and I'm finding it difficult to find much information on alcote to compare it with.

    I have read that both divosep as well as alcote are separating agents for acrylic against stone. 
    But Alcote is water based and Divosep is alginate based. 
    Does anyone know whether that has any bearing on floating clay off plaster of paris? 

    Thank you very much for all the help so far !!

    Sonja (:


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    My pleasure!

    You can still float a sculpt off a plaster of paris bust.  The more porous the stone, the easier the floating process will be, as moisture can work through the stone and to the underside of your sculpt/release agent faster.

    I'm not familiar with Divosep.  With any new material my suggestion would be to run a small test.   Take a Plaster of Paris bust, or other reasonably thick piece of Plaster of Paris, apply a few coats of the Divosep, place a small test sculpt on the sruface, and then see how well it releases after a good soak.  You may need to play with how many coats of release, or how long the bust soaks to get a process that works for you.

    As far as making your molds entirely out of dental stone, you should be fine.  Just be careful as the strength gained from pure dental stone will mean a brittle mold. Make sure to add plenty of hemp or burlap to strengthen them, and handle with care.

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    Okay awesome!! I'll be testing on my 'not so great...' spare life cast ASAP !!  :D

    And will definitely add many layers of burlap to my molds! Thanks for the tip!

    I'll post an update on how the Divosep worked for me !

    Sonja (:
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    I tested the Divosep and it worked great just like I imagine Alcote would! 
    My "test-nose" came off easily in one piece!! 

    (I coated it 3 times and that worked perfectly fine for me, but I coated the lifecast of my project 5 times just in case!!)

    So for anyone out there without access to Alcote, Divosep by Vertex works too! 

    Sonja (:
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    Awesome, glad it turned out!

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    Hey Chris! 

    I have another question about substituting epoxical!
    If I am making silicone pieces is it possible to skip the epoxical layer? Could I just use dental stone for the detail coat, and a self mixed ultracal substitute using plaster of paris and portland cement for the rest of the mould?
    Or is there maybe a different way of making the detail coat more durable other than the epoxy layer?
    -I have run a small test on trying to substitute epoxical with fibreglass resin/polyester resin but the resin didn't stick to my outer stone layer, and ended up very thin and flaking all over the place when i opened my mould. And in addition to that the fumes are really difficult to get rid of :/  

    I was also wondering whether I could run gelatine in these same moulds? either to test the moulds first/ or if I end up deciding to use gelatine for the final pieces later on.
    Are there any precautions I need to take? Or can I run both silicone and gelatine without having to worry about the materials affecting each other? 

    Thank you in advance!! (:

    Sonja (:

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    For the fiberglass I would not use any stone in the mold.  Just a nice detail coat of resin backed by a few layers of glass and possibly some syntactic dough.

    If you want to make a stone mold, you can have a bit of dental stone in your detail coat, or even go entirely dental stone for the first coat, though that is more expensive.  This mold making lesson covers using dental stone in the detail coat:  https://www.stanwinstonschool.com/tutorials/character-creation-stone-mold-making-tutorial

    Running gelatin in your mold is not a problem at all.  Unlike latex it will not inhibit any future runs of silicone you run in the mold.  Gelatin is a great and inexpensive way to test your mold prior to running a more expensive material like silicone.  I would just make sure you clean the mold after running the gelatin to make sure there is not any residue or chunks left behind.  You can also use your first test runs of gelatin to determine the volume of your mold so you know exactly how much material to mix up for future runs.

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    edited October 2017
    Hello Sonja and Chris!
    I`ve read everything you guys wrote, but I still have some doubts and you might be able to help me with. 
    I live in Brasil, and UltraCal really does not exist here, but I was thinking about mixing regular plaster with cement - 87.5% plaster and 12,5% cement. Do you think I will be able to cast latex on it? I need to make horns for a costume!

    =) Thank you so much for your help!

    Post edited by Laura Araujo on
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    Hi Laura,

    As you suggest, you can make your own UltraCal 30 by mixing plaster with various ingredients if it's not otherwise available to you.

    You just need a fine grade of plaster and make sure none of the ingredients are too coarse, or they can limit your surface detail.

    The MSDS lists the ingredients for Ultracal30 as 85% Plaster, 10% Portland Cement, 5% Silica.  

    There are people out there making their own mix without the silica though.

    I would mix up a test batch and give it a shot with a test sculpt before risking your horn sculpts.  

    You'll also want the mold to be nice and dry before you dwell latex in it, so the stone can absorb the moisture out of the liquid latex and help it form a skin.

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