Llewellyn Kouba on tue 23 nov 99
------------------
Dear Readers,
I am pouring plaster bats for the studio. I made a few last winter and want=
to
finish the project up. I put the plaster to water, all the while mixing =
with a
high speed drill. When I pour it in the mold I end up with a few with
noticeable air bubbles on the top which of course will be the surface that =
is in
contact with the clay. I don't know how much danger their is in having the
bubbles break out, leaving plaster in the clay?
Can anyone give me a hint as to how to get the bubbles of air out of the
settling plaster which heats up and hardens rather quickly.
I have giggled the mold but don't think it did much. Any helps?
Llewellyn ABBEY POTTERY
http://www.assumptionabbey.com/Pottery
Jonathan Kaplan on wed 24 nov 99
>
There are a few ways of getting the air bubbles out of the surface of your bats.
The first is to treat the interior of the female mold that you are using
with a mold dressing after treating it with a parting compound. This will
reduce the surface tension and assure a bubble free surface.
The second is to brush out the bubbles. Right after you have finsihed
pouring the plaster , grab a cheap bristle brush and go into the wet
plaster and brush the bottom surface. You can do this in round motions or
linear motions, it doesn't matter. Make sure to do this when the paster is
still wet, and clean the brush out immediately afterwards in your water
bucket, and not into the sink.
The third way is to use a pouring spout made from a piece of flashing. It
takes some figuring out how to hold the pouring bucket as well as the
spout together. The plaster pours over the sharp edge of the spout and
breaks any entraped air in the mixture.
Proper mixing techniques, type of mixer, mixer speed etc. can also help in
reducing entrapped air in the mix.
Jonathan
Jonathan Kaplan
Ceramic Design Group LTd/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
UPS: 1280 13th St. Unit13
Steamboat Springs, CO 80487
Penny Hosler on wed 24 nov 99
Hi - I used a drill when mixing my plaster for the first few molds I
made, but found the plaster set up way too fast and I had no working
time. I now just use my arm in a 5-gal bucket to mix it. And pour
it in the molds when it's just barely getting warm. Have more
jiggling time to get rid of the bubbles that way.
Penny in WA
-----Original Message-----
From: Llewellyn Kouba
To: CLAYART@LSV.UKY.EDU
Date: Tuesday, November 23, 1999 7:48 AM
Subject: Pouring Plaster Bats
----------------------------Original
message----------------------------
------------------
Dear Readers,
I am pouring plaster bats for the studio. I made a few last winter
and want to
finish the project up. I put the plaster to water, all the while
mixing with a
high speed drill. When I pour it in the mold I end up with a few with
noticeable air bubbles on the top which of course will be the surface
that is in
contact with the clay. I don't know how much danger their is in
having the
bubbles break out, leaving plaster in the clay?
Can anyone give me a hint as to how to get the bubbles of air out of
the
settling plaster which heats up and hardens rather quickly.
I have giggled the mold but don't think it did much. Any helps?
Llewellyn ABBEY POTTERY
http://www.assumptionabbey.com/Pottery
Mike Gordon on wed 24 nov 99
It sounds like your mixing too much plaster into the water, the plaster/
water ratio should give you more time to vibrate all bubbles to the
surface. I think there was a page given here on the ratios. Check the
archives. If you don't find it let me know & I'll dig it out for you.
Mike
elizabeth priddy on wed 24 nov 99
I am no expert on this, but two things to note
the bags usually say to pour the plaster into
the water and do not blend until it has all
settled into the water, this is important.
and use the side that is better, the one in the
molding container will be smoother than the back
and will absorb fine.
good luck
---
Elizabeth Priddy
email: epriddy@usa.net
http://www.angelfire.com/nc/clayworkshop
Clay: 12,000 yrs and still fresh!
On Tue, 23 Nov 1999 10:47:22 Llewellyn Kouba wrote:
>----------------------------Original message----------------------------
>------------------
>Dear Readers,
>
>I am pouring plaster bats for the studio. I made a few last winter and want to
>finish the project up. I put the plaster to water, all the while mixing with a
>high speed drill. When I pour it in the mold I end up with a few with
>noticeable air bubbles on the top which of course will be the surface that is i
>contact with the clay. I don't know how much danger their is in having the
>bubbles break out, leaving plaster in the clay?
>
>Can anyone give me a hint as to how to get the bubbles of air out of the
>settling plaster which heats up and hardens rather quickly.
>I have giggled the mold but don't think it did much. Any helps?
>
>Llewellyn ABBEY POTTERY
>http://www.assumptionabbey.com/Pottery
>
--== Sent via Deja.com http://www.deja.com/ ==--
Share what you know. Learn what you don't.
Mark & Pauline Donaldson-Drzazga on wed 24 nov 99
----- Original Message -----
From: Llewellyn Kouba
To:
Sent: 23 November 1999 15:47
Subject: Pouring Plaster Bats
----------------------------Original message----------------------------
------------------
Dear Readers,
I am pouring plaster bats for the studio. I made a few last winter and want
to
finish the project up. I put the plaster to water, all the while mixing
with a
high speed drill. When I pour it in the mold I end up with a few with
noticeable air bubbles on the top which of course will be the surface that
is in
contact with the clay. I don't know how much danger their is in having the
bubbles break out, leaving plaster in the clay?
Can anyone give me a hint as to how to get the bubbles of air out of the
settling plaster which heats up and hardens rather quickly.
I have giggled the mold but don't think it did much. Any helps?
Llewellyn ABBEY POTTERY
http://www.assumptionabbey.com/Pottery
Hi, don't use a high speed drill. Measure out the plaster (I used to use
3lbs to nearly 2pints as a ratio) and add it to cold water, slowly and
certainly not in one big dump, then stir with one hand (use the other to
scratch your nose or add a little more plaster or water as required) until
the plaster is well mixed, you can at this stage scim off any surface scum.
I have found over the years, that I can add the plaster to the water until
it starts to mound on the top of the water then stir, without needing to
mearure out quantities.
I also think the way you stir with your hand is important. I use my hand
flat down on the bottom with the palm uppermost and then give thr Royal
wave. I keep some fresh water handy to rinse off and then pour. It has
worked for me for years.
Happy potting Marek http://www.moley.uk.com
Cindy Strnad on wed 24 nov 99
Llewellyn,
Air bubbles are not a thing you want on your bat surface, but I doubt
they'll cause you a lot of trouble. Next time, keep the drill mixing end
*under* the surface, so as not to incorporate air. This is also a good idea
while mixing glazes.
One other thing I noticed is that you seem to indicate your plaster is quite
aged. It has a shelf life, and the fresher the better. Best to buy it in a
place that has a high turn-over, and only buy what you can use right away. I
hope they'll be all right, but if you find your bats are weak, this may be
part of the problem.
Cindy Strnad
Earthen Vessels Pottery
Custer, SD
Anita Rickenberg on wed 24 nov 99
To avoid air bubbles the plaster should be mixed by hand--yes, that means
being up to your elbows in plaster. There are exact measurements available
in most pottery books, but I've had good success with SLOWLY adding plaster
to the water until it mounds in the middle. After all of the mound is
thoroughly wet (it takes a minute or two), begin stirring by hand, paying
special attention to getting all the plaster on the bottom of the container
mixed. Do this while keeping your hand under the surface so air bubbles
aren't added to the mix. It's necessary to have everything ready to pour as
soon as the plaster is creamy and thick--and before it starts heating.
Anita
----- Original Message -----
From: Llewellyn Kouba
To:
Sent: Tuesday, November 23, 1999 10:47 AM
Subject: Pouring Plaster Bats
----------------------------Original message----------------------------
------------------
Dear Readers,
I am pouring plaster bats for the studio. I made a few last winter and want
to
finish the project up. I put the plaster to water, all the while mixing
with a
high speed drill. When I pour it in the mold I end up with a few with
noticeable air bubbles on the top which of course will be the surface that
is in
contact with the clay. I don't know how much danger their is in having the
bubbles break out, leaving plaster in the clay?
Can anyone give me a hint as to how to get the bubbles of air out of the
settling plaster which heats up and hardens rather quickly.
I have giggled the mold but don't think it did much. Any helps?
Llewellyn ABBEY POTTERY
http://www.assumptionabbey.com/Pottery
John Rodgers on thu 25 nov 99
Llewellyn,
Before pouring plaster again, get yourself a fair size spray bottle and fill it
denatured alcohol. After you have mixed your water and plaster in a bucket and i
thoroughly mixed, bump the bucket up and down on the floor much the way you woul
cake mix you are trying to get bubbles out of. The entrained air will collect as
bubbles and will rise to the top of the batch. Now lightly spritz the top of the
batch in the bucket with the alcohol. This will break the surface tension and ca
all the bubbles to burst. In the mold into which you are going to pour the plast
give that a lite spritz. This will again break any bubbles trapped during the po
Finally, after pour is complete, and before the plaster is set, bump the mold, t
spritz the surface of the poured plaster. The alcohol will break the remaining
bubbles.
Works for me all the time when I am making molds.
John Rodgers
In Alabama
Llewellyn Kouba wrote:
> ----------------------------Original message----------------------------
> ------------------
> Dear Readers,
>
> I am pouring plaster bats for the studio. I made a few last winter and want t
> finish the project up. I put the plaster to water, all the while mixing with
> high speed drill. When I pour it in the mold I end up with a few with
> noticeable air bubbles on the top which of course will be the surface that is
> contact with the clay. I don't know how much danger their is in having the
> bubbles break out, leaving plaster in the clay?
>
> Can anyone give me a hint as to how to get the bubbles of air out of the
> settling plaster which heats up and hardens rather quickly.
> I have giggled the mold but don't think it did much. Any helps?
>
> Llewellyn ABBEY POTTERY
> http://www.assumptionabbey.com/Pottery
Veronica Honthaas on thu 25 nov 99
Llewellyn:
After I pour the plaster in the mold I work it over with a straight edge
(my favorite one is a metal painting straight edge you buy in the hardware
store),back and forth, over and over till it is smooth with no bubbles or
bumps.
Stop this smoothing process as soon as the plaster shows the first sign of
stiffening. You end up with a very even and smooth surface. Veroncia
At 10:47 AM 11/23/99 EST, you wrote:
>----------------------------Original message----------------------------
>------------------
>Dear Readers,
>
>I am pouring plaster bats for the studio. I made a few last winter and
want to
>finish the project up. I put the plaster to water, all the while mixing
with a
>high speed drill. When I pour it in the mold I end up with a few with
>noticeable air bubbles on the top which of course will be the surface that
is in
>contact with the clay. I don't know how much danger their is in having the
>bubbles break out, leaving plaster in the clay?
>
>Can anyone give me a hint as to how to get the bubbles of air out of the
>settling plaster which heats up and hardens rather quickly.
>I have giggled the mold but don't think it did much. Any helps?
>
>Llewellyn ABBEY POTTERY
>http://www.assumptionabbey.com/Pottery
>
>
Steve Yahn on thu 25 nov 99
When I was taught to mix plaster it was to add the plaster to the water
untill it wouldn't take any more. Then to put both hands in it and mush it
around gently without spashing until it was creamy. I suspect that beating
it with a power tool may be beating air into it. And that may be the cause
of your trouble. The bubbles.
Cheer,Steve Yahn
At 10:47 AM 11/23/1999 EST, you wrote:
>----------------------------Original message----------------------------
>------------------
>Dear Readers,
>
>I am pouring plaster bats for the studio. I made a few last winter and want to
>finish the project up. I put the plaster to water, all the while mixing with a
>high speed drill. When I pour it in the mold I end up with a few with
>noticeable air bubbles on the top which of course will be the surface that
is in
>contact with the clay. I don't know how much danger their is in having the
>bubbles break out, leaving plaster in the clay?
>
>Can anyone give me a hint as to how to get the bubbles of air out of the
>settling plaster which heats up and hardens rather quickly.
>I have giggled the mold but don't think it did much. Any helps?
>
>Llewellyn ABBEY POTTERY
>http://www.assumptionabbey.com/Pottery
>
>
Llewellyn Kouba on thu 25 nov 99
RE: Plaster Bats:
Thank you Cindy and all those who have contributed to the 'pouring' of my
plaster bats. I have a few small surface bubbles but for the most part I
think the bats will serve me well. I made a few last bats last winter and
had wanted to get them all poured out now because I had heard plaster
doesn't have a long shelf life. I have received many good tips and even
something so simple as keeping the drill 'below' the surface - was something
I had not really considered. Experience is one of the best teachers and I
thank you all for such help. Clayart is truly a wonderfully good
communication and one that I would never want to be without.
Blessings and a HAPPY THANKSGIVING
-----Original Message-----
From: Cindy Strnad
To: CLAYART@LSV.UKY.EDU
Date: Wednesday, November 24, 1999 5:39 AM
Subject: Re: Pouring Plaster Bats
>----------------------------Original message----------------------------
>Llewellyn,
>
>Air bubbles are not a thing you want on your bat surface, but I doubt
>they'll cause you a lot of trouble. Next time, keep the drill mixing end
>*under* the surface, so as not to incorporate air. This is also a good idea
>while mixing glazes.
>
>One other thing I noticed is that you seem to indicate your plaster is
quite
>aged. It has a shelf life, and the fresher the better. Best to buy it in a
>place that has a high turn-over, and only buy what you can use right away.
I
>hope they'll be all right, but if you find your bats are weak, this may be
>part of the problem.
>
>Cindy Strnad
>Earthen Vessels Pottery
>Custer, SD
marc mancuso on thu 25 nov 99
Llewellyn-
When mixed properly and treated with respect plaster can be a useful thing
to have around the studio. It can also be a big mess and more trouble than
it's worth. I expect you'll hear both sides.
You describe two common problems that can be easily avoided. Motorized
mixing attachments are useful as a final brief mixing --especially when
mixing large quantities of plaster-- but overmixing or improper mixing can
cause the plaster to set up too quickly, thus making it impossible for any
bubbles normally present to float up to the surface, pop, and heal over.
Rapidly thickening plaster also makes people rush about and become nervous
if they're not used to it.
I sift all the plaster I'm going to need into motionless room temperature
water first. No motor yet. Some pause here for a while (five minutes is
plenty) to allow the dry powder to become thoroughly wetted. Mix by hand
to work out any clumps. I reach down do a wiggly-finger wave while the
back of my hand is still close to the bottom. You should be able to move
enough material to see a little disturbance at the top unless you're more
than elbow deep.
If you follow up with a motorized drill attachment, submerge the blades
first, then turn on the power. Check that the direction of the blades
forces the material down rather than up. Though it's common for there to be
some bubbles in the mixture, keep the moving blades well below the surface
of the plaster to avoid splashing more air into the mix.
If the speed is too fast, and particularly if you're using a permanently
mounted motor and the shaft is fixed, you might create a whirlpool down to
the blades. That gurgling sucking noise means that air is being brought
into the mix. Annoying while mixing glazes, definitely not good for
plaster. Decrease the speed and/or slide the bucket slowly under the shaft
to disrupt any continuous whirlpools. With experience you can tell by
looking at the slowly moving surface of the plaster during mixing to
determine whether it's properly mixed. If you're unsure, stop the motor,
pull out the attachment, and wave your hand slowly through the mix,
searching for lumps.
The whole mixing time should never need to take more than a few minutes
before you're ready to pour. A typical test is to watch what happens to the
plaster as you drag your finger across the surface. When the finger mark
softens and disappears in a few seconds, you're ready to pour. For smaller
quantities of plaster --a few gallons at the most-- it's not as crucial
when you pour, so long as it hasn't begun change consistency in the mixing
bucket. It should not be warm while in the mixing bucket; it has already
begun to get sludgy and won't fill the mold easily or well. For larger
quantities, I'd definitely recommend making a slightly thinner mix (less
plaster to water), and pouring as soon as possible after all is blended.
You want the wedging surface to be as level and as smooth as possible, and
a fairly liquid mix both levels itself out and allows any bubbles created
while pouring to float up to the surface, pop, and heal over.
Pouring plaster smoothly is tricky and can be downright unruly at larger
quantities, such as you'd be mixing for a typical wedging surface. Try to
get someone to help you tip the bucket gradually. Also try to avoid pouring
plaster from any great height. I've propped a 2x4 or similarly-shaped piece
of wood at a steep angle with one end in the empty frame. As I'm emptying
the mixing bucket, I aim the stream toward the middle of the wood to help
slow down and redistribute the weight of the pouring plaster and keep it
from exploding once it hits the bottom of the frame. Once all the plaster
is poured, I just pull out the wood piece before anything sets up. Keep in
mind that plaster in any quantity packs a hell of a punch. Be sure to seal
cracks with wet clay and provide plenty of support from the outside to all
walls of your frame. The jiggling is fun and useful and helps entice the
little bubbles to the surface. This is one place where a slightly wobbly
table is actually useful. If you have to beat on the walls of the mold, do
it gently, okay?
One last note. The ratio of plaster to water determines the density of the
final set. If you're pouring wedging surfaces or drying troughs, the
particular ratio is unimportant. You've probably heard of the method where
you sift plaster continuously into standing water until the little islands
that form don't sink. For most plaster you need in the studio, this is just
fine. This "peaking" method will most likely produce unacceptable results,
however, if you're preparing separate parts of the same slipcasting molds.
Use containers for consistent proportions, or measure stuff.
Now that everyone's eyes have glazed over, I'll step down from my soapbox.
Shameless marketing plug: My favorite book about plaster, "Mold Making for
Ceramics" by Donald Frith, appears to be available through a certain
popular online bookstore for half what I paid a few years ago. For just
under $30 bucks you won't find a more comprehensive, practical, technically
detailed work on how to use plaster safely into your studio.
Have a good holiday, everyone, filled with good food and thanksgiving.
Marc
>I am pouring plaster bats for the studio. I made a few last winter and
>want to
>finish the project up. I put the plaster to water, all the while mixing
>with a
>high speed drill. When I pour it in the mold I end up with a few with
>noticeable air bubbles on the top which of course will be the surface that
>is in
>contact with the clay. I don't know how much danger their is in having the
>bubbles break out, leaving plaster in the clay?
>
>Can anyone give me a hint as to how to get the bubbles of air out of the
>settling plaster which heats up and hardens rather quickly.
>I have giggled the mold but don't think it did much. Any helps?
>
>Llewellyn ABBEY POTTERY
>http://www.assumptionabbey.com/Pottery
Marc Mancuso
mmancuso@mit.edu
http://web.mit.edu/mmancuso/www/
"Never wrestle with a pig: You both get all dirty, and the pig likes it."
Monique Duclos on thu 25 nov 99
Hi, Llewellyn
I have always use plaster bats too, and I do them myself, but I would never
use a drill to mix the plaster and water, I use my hand and gently mix it, a
bit like you would do bread. Doing that, you try to mix without putting air
and you shouldn't have that problem any more:-)
@micalement
Monique
Monique Duclos
mduclos@hotmail.com
3757 Boul des Fondateurs
St-Isidore Nouveau-Brunswick
Canada E8M 1B5
URL: http://www.angelfire.com/mo/pmdv
------------------
Dear Readers,
I am pouring plaster bats for the studio. I made a few last winter and want
to
finish the project up. I put the plaster to water, all the while mixing
with a
high speed drill. When I pour it in the mold I end up with a few with
noticeable air bubbles on the top which of course will be the surface that
is in
contact with the clay. I don't know how much danger their is in having the
bubbles break out, leaving plaster in the clay?
Can anyone give me a hint as to how to get the bubbles of air out of the
settling plaster which heats up and hardens rather quickly.
I have giggled the mold but don't think it did much. Any helps?
Llewellyn ABBEY POTTERY
http://www.assumptionabbey.com/Pottery
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
Marvin Flowerman on fri 26 nov 99
The plaster should be sprinkled slowly into still water allowing the water to
absorb the plaster before you sprinkle more into the water. And while you
are taking the plaster into your hand you can crush any agglomerated
particles that may be present. Keep sprinkling until the plaster no longer
gets absorbed by the water. then, using a smaller vessel, a rubbber cup for
example, take out just enough plaster/water mixture to pour one bat, mix just
that amount until it is heavy cream consistancy and pour that into your bat
mold. There shouldn't be any air bubbles to trouble you with that method.
You can then proceed in the same manner for each additional bat pouring, and
the "mother load" should remain workable until you need more.
By mixing at high speed at the start, you introduce air into the mixture and
the plaster hardens much more quickly, giving you little or no time to work,
smooth the surface or do whatever else is necessary.
I suggest you try the above method and see if it dosn't help a lot. I'd be
pleased to hear how you make out.
Good luck!
Marvin Flowerman (marvpots@aol.com)
Llewellyn Kouba on sun 28 nov 99
Dear Marvin,
Hi! I didn't get at any more bat pouring yesteray or today with the
Thanksgiving holiday but will do another one tomorrow. I had been using
warm water and already on the last one I skipped the drill and mixed with a
large wire whip like the kitchen staff use and it seems to be a smoother
finish then previously. I have received so many tips but mainly I realize
the need to agitate less and get less air intrapped. I think timing is also
quite important that the bubbles can be released before the batch begins to
'heat' up and meld. Also I have found once it is set up somewhat but still
soft enough I 'trowel' the surface with a flat but sharp edge steel tool and
any small pin holes are then covered over and sealed. I am getting better
at it. Thanks for all the helps.
Llewellyn KoubaABBEY POTTERY
http://www.assumptionabbey.com/Pottery
-----Original Message-----
From: Marvin Flowerman
To: CLAYART@LSV.UKY.EDU
Date: Friday, November 26, 1999 11:49 AM
Subject: Re: Pouring Plaster Bats
>----------------------------Original message----------------------------
>The plaster should be sprinkled slowly into still water allowing the water
to
>absorb the plaster before you sprinkle more into the water. And while you
>are taking the plaster into your hand you can crush any agglomerated
>particles that may be present. Keep sprinkling until the plaster no longer
>gets absorbed by the water. then, using a smaller vessel, a rubbber cup
for
>example, take out just enough plaster/water mixture to pour one bat, mix
just
>that amount until it is heavy cream consistancy and pour that into your bat
>mold. There shouldn't be any air bubbles to trouble you with that method.
>You can then proceed in the same manner for each additional bat pouring,
and
>the "mother load" should remain workable until you need more.
>By mixing at high speed at the start, you introduce air into the mixture
and
>the plaster hardens much more quickly, giving you little or no time to
work,
>smooth the surface or do whatever else is necessary.
>
>I suggest you try the above method and see if it dosn't help a lot. I'd be
>pleased to hear how you make out.
>
>Good luck!
>
>Marvin Flowerman (marvpots@aol.com)
Jonathan Kaplan on mon 29 nov 99
Plaster is designed to mix with cold water, not warm water, not hot water,
and not unless you want the plaster to snap set on you.
It is also designed not be "troweled" as in finishing concrete.
With the correct water to plaster ratio, the correct slaking and mixing
times, the correct pouring procedure, you will have perfect plaster bats
everytime.
You can write to US Gypsum in CHicago and they will supply you with a
plaster/water/volume slide rule and as much technical information as you
care to have.
What amazes me from the many responses to this post, how many of them
contained misinformation and erroneous information. While there are
certainly many ways of doing things that may work for each and every
individual, they may not be the accepted method that will produce
consistant, predictable results that are within a defined standard.
An analogy is that while many glazes will work acceptably with their
component oxides well outside their molecular limits, it doesn't follow
that the glaze is correctly balanced. In fact, while it may work, it may
leach. The same is with plaster. I can vary my water temperature, my mixing
time, my water to plaster ratio, and still pour the material. However, the
resulting casting may be well outside the necessary absorption that it
needs to be, and the cast may be overly weak and brittle, to mention only a
few of the possible defects.
While the depth and insight of those on this list is extensive, or so it
seems, we need to be very careful in providing information that is not
correct. It might be prudent to preface your "information providing
service" by stating that ....."this is what works for me."
There is a difference in having things work for you, and having things work
for you correctly with predictable results. Understand that this is in no
way presented as an attempt to flame or discredit anyone. Many find
ceramics tuff enough. It can get even tougher with erroneous or
misinformation.
Jonathan
Jonathan Kaplan
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139
jonathan@csn,net
http://www.sni.net/ceramicdesigin
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