SierraEarthWorks on tue 18 nov 03
I have a few angel molds that are very tall and thin. Does anyone have =
any tips on the best way to pour and drain these types of mold? The mold =
keeps breaking in half when I go to remove it, right about the angels =
waistline. They are about 24 in. tall. Is one side supposed to be =
lifted off first? It breaks in the same exact spot every time. Thanks, =
Rachel
Janet Kaiser on wed 19 nov 03
Sorry to hear of your difficulty, Rachel. And they are two part
moulds? Commercially made or did you make them yourself? Answers
depend a lot on what information you give. For starters, I would
try leaving them longer to set harder... As a matter of interest,
how long are you waiting before attempting to remove the mould?
Sincerely
Janet Kaiser
*** IN REPLY TO THE FOLLOWING MAIL:
*** From: SierraEarthWorks
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*** Sent: 18/11/2003 Time: 17:24
>I have a few angel molds that are very tall and thin. Does
anyone have
>any tips on the best way to pour and drain these types of mold?
The mold
>keeps breaking in half when I go to remove it, right about the
angels
>waistline. They are about 24 in. tall. Is one side supposed to
be lifted
>off first? It breaks in the same exact spot every time. Thanks,
Rachel
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Jeff Longtin on thu 20 nov 03
Rachel,
Couple things at play here.
(First, however, is your use of the term "mold". I'm presuming your using the
term to refer to the clay piece that comes out of the mold and not the
plaster mold itself, correct?)
That said I suspect there are two culprits causing your problem: poor mold
design and POSSIBLY a short casting clay?
It sounds like the "waistline" is too severe an angle for the clay and so it
keeps breaking (cracking I would say). The only way to solve this is to take
some sandpaper and lightly sand it down until the ridge is not so problematic.
If the "waistline" is not that severe than it could be a short clay. Did you
mix the clay yourself, or have you worked with it before? Do you defloculate
the clay yourself? It sounds like your clay COULD be a tad heavy in water
(needs more defloculant). If it is than it will often show up in severe cracking
(breaking) like you describe. (Adding more defloculant, alone, at this point is
not the total solution either.) At this point you need to add more dry clay to
absorb the excess water already in the slip and then balance it with a proper
amount of defloculant.
You use the term breaking? If you are using this term deliberately than I
suspect that you are leaving the piece in the mold quite a long time before you
remove it, correct (otherwise you might use the term cracking)? It might be
possible that you are leaving the piece in the mold too long and that removing it
sooner, when it is not quite so brittle, might be better. As the piece is
long and narrow, it sounds like, it probably can come out of the mold with
"little" distortion.
In other words, leaving a short clay body in a challenging mold usually
results in excessive cracking (breaking). For this reason I usually pull porcelain
pieces out of molds while their still fairly wet. I can usually leave a
stoneware piece in a mold overnight if need be. If I do so with porcelain I will
usually have a pot in pieces when I open the mold.
take care
Jeff Longtin
Complex Molds Made Easy
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