Alternative ceramic shell recipe

Discussion in 'Investment casting Ceramic shell method' started by purpleparachute, Aug 3, 2022.

  1. Anyone tried an alternative recipe for ceramic shell e.g. molochite+sodium silicate slurry and molochites stuccos, then back up with fibreglass? sounds like it could be cheaper/easier to get hold of ...I imagine the reinforcing might be tricky but if you did it well enough maybe it would prevent/lessen cracks...hmmm

    Apparently it is used in commercial foundries...I wonder if it would survive the boil out process ...

    Thoughts anyone?
  2. Mantrid

    Mantrid Silver

    ive never tried boiling a shell to remove wax. It seems to me that 100 deg c isnt going to melt the wax quickly so the wax has time to expand and crack the shell. My prefered method is to hit the shell full blast with a burner starting from the pouring cup and working up. The wax melts almost instantly on the outside nearest the shell and flows out before it has time to expand hence reducing chance of cracks
  3. rocco

    rocco Silver

    No experience with ceramic shell so I won't comment on the viable or your recipe however I will say that sodium silicate is somewhat water soluble so a boil out would likely be a problem, a dry dewaxing would be required.
  4. I went down this rabbit hole before.

    The commercial foundries use strong chemicals to harden the shells. Ammonium chloride or sodium chloride and acid mix...nothing I want to mess with.

    Google patents can give a lot more info on the process if you want to kill a dozen hours.

    "The Water glass casting technology is from Russia. Now it is one of the most common investments casting processes in China. About 75% of foundries focus their business on water glass casting.

    "Sodium silicate react with ammonium chloride and water to produce orthosilicic acid, sodium chloride and ammonia. "

    "Ammonia is un-ionized, and has the formula NH3. Ammonium is ionized, and has the formula NH4+

    "...placed in a bath water mixed with a ammonium chloride solution."

    ...transition zone hardening bath is 24% ammonium chloride solution, the transition zone firm time is 30 min, dry 100 min after the transition zone sclerosis;
    Alternative hardening agent
    (no ammonia fumes)

    Reaction pool:

    water: 70 ~ 80 parts

    Sodium chloride powder : 15 ~ 25 parts, allow sodium chloride fully dissolve...

    ...calcium carbonate: 5 ~ 12 parts, calcium carbonate is slightly soluble in water, stirs and forms turbid solution;

    ...hydrochloric acid "concentration 36 parts and water" : 1 ~ 3 part, in turbid solution, slowly inject the hydrochloric acid of 1 ~ 3 part again, and fully stir;

    ...finally casting shell molds is put in sclerosis pond for 3-5 minute, remove, drain, allow to dry
  5. Ah that's the missing ingredient then, yeh sounds nasty I don't think I'll be trying it either. Are you just using the standard stuff now?

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