pdp1@EARTHLINK.NET on sun 2 nov 03
Hi Roxanne,
Consider more thorough wedgeing practices...which should
even things out.
If you have 'bubbles' as such, poke them with a needle-tool
or the like...
Best wishes!
Phil
Las Vegas
----- Original Message -----
From: "Roxanne Hunnicutt Ross Jesswein"
Can anyone suggest any method or a source for info on a
throwing problem I am having?
I am throwing big platters on a plaster hump. In other words
I am throwing them up side down. After I center and start to
spread the clay out past the base of the hump that I have
centered, I get a problem every time and I think it could be
about the clay being wetter in spots and drier in others.
Sometimes it feels as if I have air bubbles, but more often
the clay just acts like it is softer in some spots and
therefore has such a different consistency. Some spots
slough off and some stay higher making an even surface very
difficult to achieve.
Should I let the clay dry and throw in stages or can I do
something faster.
I am throwing big amounts of clay for me, ten pounds or so.
That makes centering hard but I still don't take too long,
just one pull up to a cone shape and then down to center.
I am just boggled!
Rox in OR
Roxanne Hunnicutt Ross Jesswein on sun 2 nov 03
CLAYART Digest - 31 Oct 2003 to 1 Nov 2003 (#2003-306)I am having a =
problem throwing.
Can anyone suggest any method or a source for info on a throwing problem =
I am having?
I am throwing big platters on a plaster hump. In other words I am =
throwing them up side down. After I center and start to spread the clay =
out past the base of the hump that I have centered, I get a problem =
every time and I think it could be about the clay being wetter in spots =
and drier in others. Sometimes it feels as if I have air bubbles, but =
more often the clay just acts like it is softer in some spots and =
therefore has such a different consistency. Some spots slough off and =
some stay higher making an even surface very difficult to achieve.=20
Should I let the clay dry and throw in stages or can I do something =
faster.
I am throwing big amounts of clay for me, ten pounds or so. That makes =
centering hard but I still don't take too long, just one pull up to a =
cone shape and then down to center.
I am just boggled!
Rox in OR
John Rodgers on sun 2 nov 03
Roxanne, you may hae two problems.
It may will be that your clay has hard spots. I work my clay by coning
it several times before starting to working out over plaster bats,
whether doing bowls or otherwise. This does helpt to even the consistency.
The other possibility is that you ahve hard spots in the plaster and the
water absorption is not uniformly the same. If the plaster is not poured
using the right technique, it will definaitely result in hard spots.
Hard spots are something that drive slip clasters crazy because the cast
for will have firm clay in one place and gooey clay in another place.
Not much you can do about it if the mold/bat has this problme, except to
get rid of it and get another.
Regards,
John Rodgers
Chelsea, AL
Roxanne Hunnicutt Ross Jesswein wrote:
>CLAYART Digest - 31 Oct 2003 to 1 Nov 2003 (#2003-306)I am having a problem throwing.
>
>Can anyone suggest any method or a source for info on a throwing problem I am having?
>
>I am throwing big platters on a plaster hump. In other words I am throwing them up side down. After I center and start to spread the clay out past the base of the hump that I have centered, I get a problem every time and I think it could be about the clay being wetter in spots and drier in others. Sometimes it feels as if I have air bubbles, but more often the clay just acts like it is softer in some spots and therefore has such a different consistency. Some spots slough off and some stay higher making an even surface very difficult to achieve.
>
>Should I let the clay dry and throw in stages or can I do something faster.
>
>I am throwing big amounts of clay for me, ten pounds or so. That makes centering hard but I still don't take too long, just one pull up to a cone shape and then down to center.
>
>I am just boggled!
>
>Rox in OR
>
>______________________________________________________________________________
>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.
>
>
>
MarjB on mon 3 nov 03
morning Roxanne
Sounds like a good idea (throwing down over a hump mold) . You do not
mention the type of clay you are using stoneware/porcelain. The good
wedging suggestions that you have received should be considered. I am
wondering if you are wetting your plaster form generously/evenly before
beginning. Uneven wicking of the moisture from the clay body might give you
some of the problems you are experiencing (especially porcelain). Maybe ?
MarjB
----- Original Message -----
From: "Roxanne Hunnicutt Ross Jesswein" <555jesswein@CHARTER.NET>
To:
Sent: Sunday, November 02, 2003 7:56 PM
Subject: Throwing large platters on a plaster base
CLAYART Digest - 31 Oct 2003 to 1 Nov 2003 (#2003-306)I am having a problem
throwing.
Can anyone suggest any method or a source for info on a throwing problem I
am having?
I am throwing big platters on a plaster hump. In other words I am throwing
them up side down. After I center and start to spread the clay out past the
base of the hump that I have centered, I get a problem every time and I
think it could be about the clay being wetter in spots and drier in others.
Sometimes it feels as if I have air bubbles, but more often the clay just
acts like it is softer in some spots and therefore has such a different
consistency. Some spots slough off and some stay higher making an even
surface very difficult to achieve.
Should I let the clay dry and throw in stages or can I do something faster.
I am throwing big amounts of clay for me, ten pounds or so. That makes
centering hard but I still don't take too long, just one pull up to a cone
shape and then down to center.
I am just boggled!
Rox in OR
____________________________________________________________________________
__
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.
Eleanora Eden on mon 3 nov 03
Hi John and all,
I have been making my own molds for many years and I have never run into
any such thing......never heard about it, either....this would certainly
turn me off the process! I can't imagine how this would happen except
using plaster with big hard lumps in it. Not sure even if I want to
know! Do people really run into this?! I was taught to sieve the plaster
into the water......use fresh plaster that has been stored properly.....I
wrap each 50# bag tightly in a heavy plastic bag when I get it so nothing
in the atmosphere can get absorbed.......
>The other possibility is that you ahve hard spots in the plaster and the
>water absorption is not uniformly the same. If the plaster is not poured
>using the right technique, it will definaitely result in hard spots.
>Hard spots are something that drive slip clasters crazy because the cast
>for will have firm clay in one place and gooey clay in another place.
>
Eleanora Eden 802 869-2003
Paradise Hill Road eeden@vermontel.net
Bellows Falls, VT 05101 www.eleanoraeden.com
John K Dellow on mon 3 nov 03
I would be inclined to throw a flat disc on a large bat. When the disc
is dry enough to picked up ,it can be
placed over the plaster hump and use a rubber rib to finnish the form.
This is way I was taught to make the cover for the top section oa a two
piece chimney pot
John.
Roxanne Hunnicutt Ross Jesswein wrote:
>CLAYART Digest - 31 Oct 2003 to 1 Nov 2003 (#2003-306)I am having a problem throwing.
>
>Can anyone suggest any method or a source for info on a throwing problem I am having?
>
>I am throwing big platters on a plaster hump. In other words I am throwing them up side down. After I center and start to spread the clay out past the base of the hump that I have centered, I get a problem every time and I think it could be about the clay being wetter in spots and drier in others. Sometimes it feels as if I have air bubbles, but more often the clay just acts like it is softer in some spots and therefore has such a different consistency. Some spots slough off and some stay higher making an even surface very difficult to achieve.
>
>
>
>
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
John Rodgers on tue 4 nov 03
Hi,
There are a lot of things that can result in hard spots. Old plaster,
plaster mixed together from bags of different batch numbers, and widely
different ages, plaster with lumps not screened out. Different kinds of
plasters mixed accidentally, using highly mineralized water.
Just making sure the plaster is fresh, properly stored, and using good
water makes all the difference.
Something I got started doing a long time ago after some frustrating
experiences with getting shipments of old plaster from suppliers is to
request materials verifying the age of the plaster. The suppliers
interest is more in turning old inventory rather than seeing that the
buyer gets the newest materials. This is understandable but is a
conflict of interest so far as I am concerned. I want the newest and
freshest plaster, and the supplier wants to get rid of the old stuff so
he doesn't have to dump it and take a loss. The only way to get around
that is to match batch numbers, dates, etc. and make that a requirement
of purchase. I have had to throw out a lot of plaster before I got that
down right. I simply won't buy from sources that won't co-operate with
me on this.
And congrats on being a moldmaker!! We are a unique group.!!
Regards,
John Rodgers
Chelsea, AL
Eleanora Eden wrote:
> Hi John and all,
>
> I have been making my own molds for many years and I have never run
> into any such thing......never heard about it, either....this would
> certainly turn me off the process! I can't imagine how this would
> happen except using plaster with big hard lumps in it. Not sure even
> if I want to know! Do people really run into this?! I was taught to
> sieve the plaster into the water......use fresh plaster that has been
> stored properly.....I wrap each 50# bag tightly in a heavy plastic bag
> when I get it so nothing in the atmosphere can get absorbed.......
>
>
>> The other possibility is that you ahve hard spots in the plaster and the
>> water absorption is not uniformly the same. If the plaster is not poured
>> using the right technique, it will definaitely result in hard spots.
>> Hard spots are something that drive slip clasters crazy because the cast
>> for will have firm clay in one place and gooey clay in another place.
>>
>
> Eleanora Eden 802 869-2003
> Paradise Hill Road eeden@vermontel.net
> Bellows Falls, VT 05101 www.eleanoraeden.com
>
John Rodgers on tue 4 nov 03
Hi!
Here is more on the subject of hard spots in molds. I dug uut my
collection of moldmaking notes and found this.
"US Gypsum Bulletin TAC 161
POURING:
To prevent anir entrainment and provide a uniform, smooth surface,
careful pouring or the plaster slurry is necessary. Agitation of the
filled case mold is a further step used to prevent air at or near the
mold surface. Whenever possible, the plaster slurry should be poured
carefully in one corner so slurry flows across the surface of the case
mold. Pouring a large amount of slurry directly on the face of the case
mold may result in slight desnification of the plaster mold at the point
where it first strikes the surface of the case. This produces a hard
spot giving uneven absorption."
US Gypsum has a most excellent set of technical bulletins on their
plaster and cement products and applications. Anyone wishing to work
with molds for clay work should definitely avail themselves of these
bulletins.
Also available are the Volume and Mix Calculators, a type of slide rule
that really makes life easier for the mold maker.
The address is:
United States Gypsum
Tooling and Casting Division
101 South Wacker Drive
Chicago, IL 60606
Regards,
John Rodgers
Chelsea, AL
Eleanora Eden wrote:
> Hi John and all,
>
> I have been making my own molds for many years and I have never run
> into any such thing......never heard about it, either....this would
> certainly turn me off the process! I can't imagine how this would
> happen except using plaster with big hard lumps in it. Not sure even
> if I want to know! Do people really run into this?! I was taught to
> sieve the plaster into the water......use fresh plaster that has been
> stored properly.....I wrap each 50# bag tightly in a heavy plastic bag
> when I get it so nothing in the atmosphere can get absorbed.......
>
>
>> The other possibility is that you ahve hard spots in the plaster and the
>> water absorption is not uniformly the same. If the plaster is not poured
>> using the right technique, it will definaitely result in hard spots.
>> Hard spots are something that drive slip clasters crazy because the cast
>> for will have firm clay in one place and gooey clay in another place.
>>
>
> Eleanora Eden 802 869-2003
> Paradise Hill Road eeden@vermontel.net
> Bellows Falls, VT 05101 www.eleanoraeden.com
>
Craig Dunn Clark on tue 4 nov 03
I was having a problem with the setting time of some plaster that I had
stored and finally decided to call the folks at USG and RTFM (read the
*&$%@#%&^ manual.) The tech guy with whom I spoke infomed me that the
plaster that I was using was most likely "seeded," meaning that it had
absorbed moisture form the atmosphere and that it is not the best idea to
use plaster that has been opened and stored, especially ir it is not wrapped
very well in as airtight and dry an environment as possible.
Went over to the clay store, bought another coupla bags (the stuff is
cheap in this neck o the woods), and, viola, problem solved.
I was also informed that the only real way to properly mix the plaster
and water is by weighing each prior to mixing. He said that the old
"...sprinkle the plaster into the water technique until a small mountain
peak forms just isn't accurate or consistent enough."
As to the specific problem with the uneveness in plaster mix it sounds
like a seeding problem to me. Just get some fresh plaster and have a go at
it again.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Eleanora Eden"
To:
Sent: Monday, November 03, 2003 3:10 PM
Subject: Re: Throwing large platters on a plaster base
> Hi John and all,
>
> I have been making my own molds for many years and I have never run into
> any such thing......never heard about it, either....this would certainly
> turn me off the process! I can't imagine how this would happen except
> using plaster with big hard lumps in it. Not sure even if I want to
> know! Do people really run into this?! I was taught to sieve the plaster
> into the water......use fresh plaster that has been stored properly.....I
> wrap each 50# bag tightly in a heavy plastic bag when I get it so nothing
> in the atmosphere can get absorbed.......
>
>
> >The other possibility is that you ahve hard spots in the plaster and the
> >water absorption is not uniformly the same. If the plaster is not poured
> >using the right technique, it will definaitely result in hard spots.
> >Hard spots are something that drive slip clasters crazy because the cast
> >for will have firm clay in one place and gooey clay in another place.
> >
>
> Eleanora Eden 802 869-2003
> Paradise Hill Road eeden@vermontel.net
> Bellows Falls, VT 05101 www.eleanoraeden.com
>
>
____________________________________________________________________________
__
> 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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