air bubbles in mold material

[rodney]

i saw and felt some tiny bumps on a pices of cast glass, and was wondering, are these caused from tiny air bubbles in the mold material,,,,,,,,,is is possible to coat the wax model, or whatever the master that is to be cast, with the BE KILN WASH to give it a BUBBLE FREE BARRIER between the master and the mold material

thanks
rodney

[Lauri Levanto]

Rodney,
bubbles themself has two properties. If you get enough of
them, the mold is porous and can breathe the
expanding air from the cavity. This is what Lundstrom
recommends. These are good bubbles.

Single bubbles in the mold mix, if not breathing, may
crack the mold when the gasses expands. Near the inner surface they may collapse, and a glass bump results.
These are bad bubbles.

Using kiln wash as the innermost layer helps only
if it matures hard enough. One must learn to
cast the mold without bubbles.

I have used diluted kiln wash - or gypsum+AlO - after
making the mold. I fill the mold and pour out
immediately. The mold wall absorbs moisture and
a smooth surface coating is left. Very tiny bubbles are
completely filled and smoothed out.

-lauri

[ellen abbott]

Spritz your model with a de-bubblizer before pouring the plaster. It breaks the surface tension and allows the bubbles to rise up when you gently vibrate the mold mix after pouring and before it starts to harden.

Also, if they are very small bumps, simply take a small diamond point and grind them off and then buff.

e

[Jerry]

Okay, Ellen, let's get technical; exactly what is a De-Bubbleizer?

Jerry

[Brad Walker]

Okay, Ellen, let's get technical; exactly what is a De-Bubbleizer?

There are a number of products available for minimizing bubbles in plaster. In most cases, you wet the model or rubber mold with the "de-bubbleizer" before pouring in the plaster. It makes it easier for the bubbles to vibrate free after you've poured.

I don't know which product Ellen uses, but two that I'm familiar with are Bubble-B-Gone and Mold Rinse.

[Ian]

The best debubbleizer is washup liquid thinned down to water consistency or use a camelhair brush,wet it and wipe it across a bar of soap and paint it on to your wax model
Regards
Ian

[ellen abbott]

Okay, Ellen, let's get technical; exactly what is a De-Bubbleizer?

What he (Brad) said and Casper. It is soapy in nature. I don't know what brand we use either. The label is faded to the extreme and my tech man had a memory loss. Probably got it from a foundry supply.

E

[watershed]

A fellow grad showed me how, tonight. Once you pull the mold, palster still damp, you can hose the mold down, then take a brush and fill the holes with additional plaster. It ONLY works if you hose the mold.

Greg