marci Boskie's Mama =^..^= on wed 8 feb 06
At 11:00 PM 2/8/2006, you wrote:
>From: CHRISTINE LAGINESS
>Subject: pouring slip
>I have begun working with a porcelain pouring slip. This has been a
>challenge, but I finally bit the bullet and bought a hydrometer. There is
>one weird problem that I am experiencing. When I am pouring the slip out
>of the mold after it has developed the desired thickness I have a
>dificult time getting the slip to slide out, i have to insert a stick into
>the opening, only then will it start to flow. When I open the mold the
>next day the round shape that I am trying to achieve has a dented in side.
>
>Someone thought that the slip and mold were building up a suction. Can
>anyone help me with this?
>
>christine
Hi Christine,
Yes, thats what's happening... Letting the slip "glug" out of the
mold when you empty it will cause a suction that will cause the casting to
collapse... Get a straw or better still, a flexible piece of small plastic
tubing ( available from any pet store... They use it for fish tanks)
.....and when youre ready to empty the mold, insert the tubing being
careful to not touch the sides of the mold and gently blow to break
the suction . The slip should start to flow out of the mold .
Marci Blattenberger Boskie's Mama =^..^=
http://www.marciblattenberger.com
marci@ppio.com
Porcelain Painters International Online http://www.ppio.com
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John Rodgers on wed 8 feb 06
Christine,
It sounds like you have a couple of problems.
Porcelain can be thixotropic. That is the property exhibited by certain
gels of becoming fluid when stirred or shaken and returning to the
semisolid state upon standing. The porcelain may be returning to a
jell in the mold. This will most likely occur if your deflocculation
isn't just right. You may need to adjust it.
You mentioned having gotten a hydrometer - *get rid of it!!* Wrong tool
for working with porcelain. It is not accurate enough. What you need is
a viscosimeter and you can get one from Laguna clay for about $12 for a
glass one and $25 for a plastic one. With this and a gram scale you can
get the porcelain deflocculation, flow rate and density numbers dead on.
When you do that, the porcelain will be a pure joy to work with.
After the porcelain is adjusted properly, then draining the mold
properly is the next step.
If you quickly turn the mold upside down, the draining action will
create a suction that will pull the newly formed porcelain piece away
from the mold. When you drain a mold, turn it over slowly to the fully
vertical position. This allows most of the porcelain slip to drain with
plenty of venting so you don't get that suction
Here is the web site at Laguna Clay for a PDF file titled The Art of
Slip Making. It is easy to understand and will tell you everything you
really need to know. AND, it addresses the issue of the hydrometer
http://www.lagunaclay.com/volumev/artslip.pdf
I began my career in clay with porcelain slip 20 years ago and work with
it to this day. It is a wonderful medium.
Good luck with your work.
John Rodgers
Chelsea, AL
CHRISTINE LAGINESS wrote:
>hi
>
>I have begun working with a porcelain pouring slip. This has been a challenge, but I finally bit the bullet and bought a hydrometer. There is one weird problem that I am experiencing. When I am pouring the slip out of the mold after it has developed the desired thickness I have a dificult time getting the slip to slide out, i have to insert a stick into the opening, only then will it start to flow. When I open the mold the next day the round shape that I am trying to achieve has a dented in side.
>
>Someone thought that the slip and mold were building up a suction. Can anyone help me with this?
>
>christine
>
>
>
>
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CHRISTINE LAGINESS on wed 8 feb 06
hi
I have begun working with a porcelain pouring slip. This has been a challenge, but I finally bit the bullet and bought a hydrometer. There is one weird problem that I am experiencing. When I am pouring the slip out of the mold after it has developed the desired thickness I have a dificult time getting the slip to slide out, i have to insert a stick into the opening, only then will it start to flow. When I open the mold the next day the round shape that I am trying to achieve has a dented in side.
Someone thought that the slip and mold were building up a suction. Can anyone help me with this?
christine
---------------------------------
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asim mahmood on thu 9 feb 06
Try and ensure the followings :-
1. Reduce the thickness of pot if possible and by this way the slip can be
taken out without the use of STICK but still you will have to clear off the
mouth of the mold with something for the smooth flow out.
2. Do not give too much time after pouring out the slip and open the mold
once it is Just leather hard.
I am sure it would work.
Asim Mahmood.
>From: CHRISTINE LAGINESS
>Reply-To: Clayart
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: pouring slip
>Date: Wed, 8 Feb 2006 20:16:25 -0800
>
>hi
>
>I have begun working with a porcelain pouring slip. This has been a
>challenge, but I finally bit the bullet and bought a hydrometer. There is
>one weird problem that I am experiencing. When I am pouring the slip out
>of the mold after it has developed the desired thickness I have a dificult
>time getting the slip to slide out, i have to insert a stick into the
>opening, only then will it start to flow. When I open the mold the next
>day the round shape that I am trying to achieve has a dented in side.
>
>Someone thought that the slip and mold were building up a suction. Can
>anyone help me with this?
>
>christine
>
>
>
>
>---------------------------------
> Yahoo! Mail - Helps protect you from nasty viruses.
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
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Snail Scott on sat 11 feb 06
At 08:16 PM 2/8/2006 -0800, you wrote:
>...When I am pouring the slip out of the mold after it has developed the
desired thickness I have a dificult time getting the slip to slide out, i
have to insert a stick into the opening, only then will it start to flow.
When I open the mold the next day the round shape that I am trying to
achieve has a dented in side.
Casting slips are thixotropic, and porcelain slips
often more so than most. This means that it will
have a higher viscosity when sitting still than
when it is agitated, such as when stirred or while
pouring. Shaking or vibrating the mold can have a
similar effect, but you can also use the stick method,
just to get it flowing.
Are you stirring the slip in the mold after you turn
it over to pour out? Bad! Don't wait to use the stick
until you've got it upside-down; get it liquified by
jolting the mold or using the stick before you try to
pour, then pour slowly to let the air in as you pour.
It's a little like getting ketchup out of the bottle -
ever stick a knife in, to make an air channel so that
the ketchup can flow? Ketchup can't come out unless air
can get in to displace its volume. And you keep the
bottle at only a slight angle, so that the air can keep
entering, and it doesn't blop all over the table when
it starts. Don't upend the ketchup/slip mold until
it's almost empty. Then it's OK, because there's not
enough ketchup/slip left to block the orifice. ;)
-Snail
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