Louis Katz on sat 1 nov 03
Have you tried a light spray of 1 Tablespoon of rubbing alchohol in a
quart of water just before pouring in the plaster? Cuts the surface
tension enough to allow the bubbles to float off the form. Jewlers use
it when investing wax. This trick seems to have helped me.
Louis
On Saturday, November 1, 2003, at 08:16 AM, Jeff Longtin wrote:
> As I've been pouring lately I've noticed this batch of plaster seems to
> develop air bubbles on a regular basis. I have the two simple options;
> add more
> water to the mix to keep the pour more fluid (but that creates a
> weaker plaster)
> or I can pour sooner, i.e. mix less (but that too creates a weaker
> plaster).
> And so I'm resorting to option number # 3: Manually move the air
> bubbles.
>
> Oddly, I've never seen this mentioned in any plaster book so I'll
> share it
> with you all here. After you have poured the plaster, stick your hand
> IN the
> plaster and rub your fingers along the molded form, basically rubbing
> the form
> with your fingers. This will move the air bubbles away from the mold
> face so you
> can produce a air bubble free mold. (Be sure to do this while the
> plaster is
> still fairly liquid.)
>
> Typically mold books will tell you to "tap the bucket" to remove air
> bubbles
> but, as anyone with any regular experience with plaster will tell you,
> that is
> a waste of time in many instances.
>
> A couple years ago I was more active in my mold making for outside
> parties.
> One such party was a plaster/cement statuary shop just north of
> minneapolis.
> (If you needed a slip casting mold they sent you to me, if you needed
> a latex
> mold I sent you to them.) One day, as I was delivering some molds, I
> walked in
> to see Bill sticking his fingers in some just poured plaster.
> Credulously, I
> asked Bill, "What are you doing?", he explained that it was the
> fastest way he
> knew to remove bubbles so he did it that way. "Damn!", I thought,
> "Never
> thought of doing THAT!".
> Amazing what you learn from the other side!
>
> Curiously, for years I had air bubble problems with my slip cast work,
> my
> teapot in particular, has a strong shoulder which always wants to trap
> air
> bubbles. (I even called the folks at Kohler to see if they had any
> thoughts.)
>
> Damn, if the finger trick doesn't work with casting slip as well!
>
> I was this close to tossing in my teapot design because of my air
> bubble
> problem (I must have spent about ten years thinking there was no
> solution.) Damn,
> if it doesn't hurt to apply different technologies to what we do.
>
> take care gang
> Jeff Longtin
> in sunny minneapolis
> still excited to get into the studio on a saturday morning,
> WHAT on earth is that about?
> 20+ years I've been dealing with all sorts of headaches and still
> excited to
> get back at it!
> I must be mad!
>
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Jeff Longtin on sat 1 nov 03
As I've been pouring lately I've noticed this batch of plaster seems to
develop air bubbles on a regular basis. I have the two simple options; add more
water to the mix to keep the pour more fluid (but that creates a weaker plaster)
or I can pour sooner, i.e. mix less (but that too creates a weaker plaster).
And so I'm resorting to option number # 3: Manually move the air bubbles.
Oddly, I've never seen this mentioned in any plaster book so I'll share it
with you all here. After you have poured the plaster, stick your hand IN the
plaster and rub your fingers along the molded form, basically rubbing the form
with your fingers. This will move the air bubbles away from the mold face so you
can produce a air bubble free mold. (Be sure to do this while the plaster is
still fairly liquid.)
Typically mold books will tell you to "tap the bucket" to remove air bubbles
but, as anyone with any regular experience with plaster will tell you, that is
a waste of time in many instances.
A couple years ago I was more active in my mold making for outside parties.
One such party was a plaster/cement statuary shop just north of minneapolis.
(If you needed a slip casting mold they sent you to me, if you needed a latex
mold I sent you to them.) One day, as I was delivering some molds, I walked in
to see Bill sticking his fingers in some just poured plaster. Credulously, I
asked Bill, "What are you doing?", he explained that it was the fastest way he
knew to remove bubbles so he did it that way. "Damn!", I thought, "Never
thought of doing THAT!".
Amazing what you learn from the other side!
Curiously, for years I had air bubble problems with my slip cast work, my
teapot in particular, has a strong shoulder which always wants to trap air
bubbles. (I even called the folks at Kohler to see if they had any thoughts.)
Damn, if the finger trick doesn't work with casting slip as well!
I was this close to tossing in my teapot design because of my air bubble
problem (I must have spent about ten years thinking there was no solution.) Damn,
if it doesn't hurt to apply different technologies to what we do.
take care gang
Jeff Longtin
in sunny minneapolis
still excited to get into the studio on a saturday morning,
WHAT on earth is that about?
20+ years I've been dealing with all sorts of headaches and still excited to
get back at it!
I must be mad!
Snail Scott on sat 1 nov 03
At 09:16 AM 11/1/03 EST, you wrote:
>After you have poured the plaster, stick your hand IN the
>plaster and rub your fingers along the molded form, basically rubbing the
form
>with your fingers. This will move the air bubbles away from the mold face
so you
>can produce a air bubble free mold.
I use one of those cheap hog-bristle brushes
to do this - the 40-cent ones from the
hardware store. (About 5.00 for a case of
two dozen from Harbor Freight.) I sometimes
make molds over wet clay or plasticine, and
I can avoid accidental surface damage from
fingernails more easily this way. My nails
are as short as they can get, but it seems
I'm always forgetting some bit of contour
at the wrong time! ;) I do use fingers
for the quick-and-dirty or solid stuff,
though.
-Snail
Martinb888@AOL.COM on mon 3 nov 03
I used to use a crude but effective vacuum chamber to remove the bubbles before pouring plaster; use a 5 gal bucket to mix the plaster, cut a hole in the lid the right size for a shop Vac hose, let er rip. Don't use so much plaster that you suck it up, I'm sure you could kill your shop vac. I made a clear cover out of plexi so I could watch the bubbles come out.
On Saturday, November 1, 2003, at 08:16 AM, Jeff Longtin wrote:
> As I've been pouring lately I've noticed this batch of plaster seems to
> develop air bubbles on a regular basis.
Martin Butt
clayncolor@aol.com
CoyoteClay.com
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