John Rodgers on sat 1 nov 03
Jeff Longtin is right on about the fingers thing, for both plaster and
slip. However, for the plaster, there is another solution.
I don't like the stuff on my hands when I'm having to handle or
manipulate things involved in a plaster pour. So, here is what I do.
First, put some methanol alcohol (isopropal is prol'ly just as good,
but I happened to have the methanol for working with shellac) in a spray
bottle for use. Then,
1) After mixing, bump the plaster bucket (works on the slip bucket as
well) up and down on the floor like you would a cake mix. This makes the
bubbles rise to the surface.
2) Spritz the surface of the plaster in the bucket. This will burst all
the bubbles floating there. Then Bump the bucket again for a couple of
times. Spritz again.
3) Spritz the surface of the mold for the plaster pour with an alcohol
mist - do not saturate!!!!! This doesn't work for slip molds as the slip
mold surface is not sealed.
4) Begin the plaster pour. Make it a continuous pour once you start.
Otherwise a line may form in the mold.
5) Start your pour in the deepest part of the mold. The movement of the
plaster as it fills towards the upper part helps to further smooth the
plaster mold surface and reduce bubbles. Lightly bumping the pouring
table while pouring the plaster also reduces bubbles at the mold surface.
5) When the mold is full, after the plaster stiffens slightly, use a
straight edge tool to level and smooth the surface. I use a very large
mold knife laid well over towards it's side and draw it across two or
three times to make a very smooth, shiny, closed surface. Gives it a
professional look.
I once tried to get rid of bubbles by using a vacuum casting machine to
remove air. Major overkill!!!! Made the plaster boil in the bucket and
made a mess. Not necessary. The proceedure above works just fine. Apply
the KISS principle and you get along just fine with this.
Hope this helps by adding to the compilation of knowledge of molds and
mold making in the Clayart Archives.
Regards,
John Rodgers
Chelsea, AL
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