Casting Investment Question

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    I am shopping for investment materials and all of my references call for silica “flour” 325 mesh.  The closest supplier that I can get pottery plaster and silica from calls the product silica “sand” 325 mesh.  I am hoping that the important thing here is the mesh size, not the name Undecided  Casters, what do you say?



    Jan – silica flour is made by crushing silica sand.  

    Ask them if it has a gritty or powdery texture.  If they answer powdery then I think you are okay.

    Helios Kiln Glass Studio



    Thanks Paul!  Unfortunately, the small ceramics shop that I purchased from did not have the item in stock, they had to order from their supplier.  If it turns out that I get sand, can I cast my mold and then do a “slip coat” of pure pottery plaster or kiln wash to soften the side where the glass will touch?


    I don’t know if the kiln wash will work. I do know that you can buy Satin Cast (original) which will give you a very smooth finish. It’s made for metal casting, but it works well with glass.

    Mixing your own is certainly much cheaper and I have had good results from home-made mixtures. The finish is not as smooth as Satin Cast, but I have been able to smooth out the interior with fingers, cloth, cotton swabs, and the makeup sponges available in the cosmetic aisles.

    When that fails, fire polishing helps. The “tooth” that the homemade investments leave is something which can add to the final item. It really is a matter of taste and application.



    Substitue diatamaceous earth for silica. Dennis

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