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how to keep goblets from seperating...

updated fri 29 nov 02

 

Dannon Rhudy on sun 24 nov 02


Tommy Humphries said:

Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...>
> the way I make goblets and other stemmed items is to make the top section
> and let it dry to leather hard >and.... attach a piece of clay and throw
the
foot.......>

Tommy's method is the best in my experience. An
added advantage is that the foot will be on STRAIGHT.
Much less liklihood of "tilt" in the finished product.

regards

Dannon Rhudy

Paul on sun 24 nov 02


Hello,
I have a lot of goblets that seperate during the bisque firing, then i have
to glaze the stem and cup back together in the glaze firing. It usually
works fine but i am wondering if anyone else had this problem and how to
prevent it? I have dried them and fired them very slowly and it still
happens. The same thing happens with pedestal bowls i make as well. Any
ideas?
Paul B

Judith S. Labovitz on sun 24 nov 02


Paul...spooze often works for me.. I slosh it on after scoring and then
attach the parts, and dry very slowly.....

Judy....in central Michigan


At 11:12 AM 11/24/02 -0500, you wrote:
>Hello,
>I have a lot of goblets that seperate during the bisque firing, then i have
>to glaze the stem and cup back together in the glaze firing. It usually
>works fine but i am wondering if anyone else had this problem and how to
>prevent it? I have dried them and fired them very slowly and it still
>happens. The same thing happens with pedestal bowls i make as well. Any
>ideas?
>Paul B
>
>______________________________________________________________________________
>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.

Wood Jeanne on sun 24 nov 02


Hi Paul,
A number of years ago I had this problem too. A friend
suggested maybe an air bubble was captured between cup
& stem. She suggested releasing it by pushing a pin
tool horizontally between them after they were placed
together (with slipping & scoring of course). Then
smoothing over the small hole.
This worked fairly well for me. But over the years
I've found I don't need to continue this practice
which makes me think that at least part of keeping
stems and cups together is repeated experience.
Have fun with them.
Regards,
Jeanne W.

--- Paul wrote:
> Hello,
> I have a lot of goblets that seperate during the
> bisque firing, then i have
> to glaze the stem and cup back together in the glaze
> firing. It usually
> works fine but i am wondering if anyone else had
> this problem and how to
> prevent it? I have dried them and fired them very
> slowly and it still
> happens. The same thing happens with pedestal bowls
> i make as well. Any
> ideas?
> Paul B
>
>
______________________________________________________________________________
> 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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Tommy Humphries on sun 24 nov 02


if the goblets are separating, then the joint is made weak...

the way I make goblets and other stemmed items is to make the top section
and let it dry to leather hard and do a bit of trimming. do not trim the
bottom too thin, leave it just a bit thick, unless you are making a solid
stem...how dry it needs to be will become evident later, i like to let it
dry to a good chocolate consistency... tap it to center on the wheel head
and secure with clay wads.

take a bit of thick slip from the splash pan, or make some from some dried
trimmings and a bit of vinegar, swab the bottom of the pot with the slip
and let it set up a bit.

weigh out enough clay for the stem/foot and wedge a bit of slip into it to
make it quite soft...then form it into a shape sort of like a mortar, from a
mortar and pestle...

set the wheel in motion very slowly and press the rounded end of the clay
for the stem into the center of the rotating upper section, and hold it
there pressing gently but firmly until the clay grabs hold of the pot. at
this point the clay is joined as well as it will ever be, all that is left
to do is finish off the joint, and form the pedestal and foot.

using this method, I haven't had a goblet stem joint fail in several years.

Tommy

Marshall ,Texas

Leland G. Hall on mon 25 nov 02


Hi Tommy. You said:
"take a bit of thick slip from the splash pan, or make some from some dried
trimmings and a bit of vinegar, swab the bottom of the pot with the slip
and let it set up a bit."

I was shown to use a bit of sodium silicate in slip for joining. How does
vinegar work? And why? Would one be better than the other? Thanks.

Leland Hall
Before The Wheel Enterprises
La Pine, Oregon, USA

Culling on mon 25 nov 02


What onearth is "spooze" Is it catching? Related to sleeping sicknes?...:)
lol
Steph
----- Original Message -----
From: Judith S. Labovitz
To:
Sent: Monday, November 25, 2002 2:19 AM
Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...


> Paul...spooze often works for me.. I slosh it on after scoring and
then
> attach the parts, and dry very slowly.....
>
> Judy....in central Michigan
>
>
> At 11:12 AM 11/24/02 -0500, you wrote:
> >Hello,
> >I have a lot of goblets that seperate during the bisque firing, then i
have
> >to glaze the stem and cup back together in the glaze firing. It usually
> >works fine but i am wondering if anyone else had this problem and how to
> >prevent it? I have dried them and fired them very slowly and it still
> >happens. The same thing happens with pedestal bowls i make as well. Any
> >ideas?
> >Paul B
> >
>
>___________________________________________________________________________
___
> >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.
>
>
____________________________________________________________________________
__
> 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.
>

Autumn Downey on mon 25 nov 02


If the popping off problem is not to do with some forming process, then it could be the slip or water that you've been using. I don't know the relative merits of vinegar vs sodium silicate, but I have experienced mug handles popping off with slip - that held too much water. (Carefully avoiding using one of the two terms that I always confuse). I now use either water with trisodium phosphate in it or the magic water solution that should be in the Clayart Archives.

It makes a difference. I think vinegar works similarly, though for some reason I've formed an attachment (so to speak) to these two solutions.

Autumn Downey
Yellowknife, NWT

At 01:08 AM 2002-11-25 -0500, you wrote:
>Hi Tommy. You said:
>"take a bit of thick slip from the splash pan, or make some from some dried
>trimmings and a bit of vinegar, swab the bottom of the pot with the slip
>and let it set up a bit."
>
>I was shown to use a bit of sodium silicate in slip for joining. How does
>vinegar work? And why? Would one be better than the other? Thanks.
>
>Leland Hall
>Before The Wheel Enterprises
>La Pine, Oregon, USA
>
>______________________________________________________________________________
>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.
>
>
Yellowknife Guild of Arts and Crafts website:
http://users.internorth.com/~downeya/index.html

Tommy Humphries on mon 25 nov 02


I think they work about the same, vinegar is just a lot cheaper and easier
to get

Tommy


----- Original Message -----
From: "Leland G. Hall"
To:
Sent: Monday, November 25, 2002 12:08 AM
Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...


> Hi Tommy. >
> I was shown to use a bit of sodium silicate in slip for joining. How does
> vinegar work? And why? Would one be better than the other? Thanks.
>
> Leland Hall
> Before The Wheel Enterprises
> La Pine, Oregon, USA
>
>
____________________________________________________________________________
__
> 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.
>

Leland G. Hall on tue 26 nov 02


Somebody on the list I'd bet, know the answer to this.


Ok, I think I get it now. Either vinegar or Sodium Silicate in slip, for
joining clay, acts as a dufloculant, so that there is "more clay" in the
slip than if a defloc was not used. Hence stronger joints. Is that it?
Anybody? But some one suggested to me that Sodium Silicate has its
own "adhesive" properties in clay slip, and might provide an even stronger
joint. Is this so?

Leland Hall
Before The Wheel Enterprises
La Pine, OR USA

On Mon, 25 Nov 2002 21:25:37 -0600, Tommy Humphries
wrote:

>I think they work about the same, vinegar is just a lot cheaper and easier
>to get
>
>Tommy
>
>
>----- Original Message -----
>From: "Leland G. Hall"
>To:
>Sent: Monday, November 25, 2002 12:08 AM
>Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...
>
>
>> Hi Tommy. >
>> I was shown to use a bit of sodium silicate in slip for joining. How
does
>> vinegar work? And why? Would one be better than the other? Thanks.
>>
>> Leland Hall
>> Before The Wheel Enterprises
>> La Pine, Oregon, USA
>>
>>
>___________________________________________________________________________
_
>__
>> 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.
>>
>
>___________________________________________________________________________
___
>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.

Rebecca P on tue 26 nov 02


Hi Leland!

How are ya? I don't think I can answer your question as much as complicate
it, but here goes. We always used vinegar when I was taking classes. But
recently, I picked up somewhere that Epsom Salts help (May have picked that
up on this list) That is Magnesium Sulfate - and I know zilch about
chemistry - and I have not tried it yet. Big help I am, huh? Oh well, I was
interested enough to try to help.

Cheers,
Rebecca Pierre
Oak Island, NC







>From: "Leland G. Hall"
>Reply-To: No title defined
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...
>Date: Tue, 26 Nov 2002 11:55:48 -0500
>
>Somebody on the list I'd bet, know the answer to this.
>
>
>Ok, I think I get it now. Either vinegar or Sodium Silicate in slip, for
>joining clay, acts as a dufloculant, so that there is "more clay" in the
>slip than if a defloc was not used. Hence stronger joints. Is that it?
>Anybody? But some one suggested to me that Sodium Silicate has its
>own "adhesive" properties in clay slip, and might provide an even stronger
>joint. Is this so?
>
>Leland Hall
>Before The Wheel Enterprises
>La Pine, OR USA
>
>On Mon, 25 Nov 2002 21:25:37 -0600, Tommy Humphries
>wrote:
>
> >I think they work about the same, vinegar is just a lot cheaper and
>easier
> >to get
> >
> >Tommy
> >
> >
> >----- Original Message -----
> >From: "Leland G. Hall"
> >To:
> >Sent: Monday, November 25, 2002 12:08 AM
> >Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...
> >
> >
> >> Hi Tommy. >
> >> I was shown to use a bit of sodium silicate in slip for joining. How
>does
> >> vinegar work? And why? Would one be better than the other? Thanks.
> >>
> >> Leland Hall
> >> Before The Wheel Enterprises
> >> La Pine, Oregon, USA
> >>
> >>
> >___________________________________________________________________________
>_
> >__
> >> 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.
> >>
> >
> >___________________________________________________________________________
>___
> >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.
>
>______________________________________________________________________________
>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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James Bledsoe on tue 26 nov 02


you are getting it but need to understand a little more.
the vinegar will make clay floc together and sodium silicate de floc in
other words vinegar (acid) makes clay water attract clay particals and
sodium silicate(basic) causes clay particals to repel
----- Original Message -----
From: "Leland G. Hall"
To:
Sent: Tuesday, November 26, 2002 8:55 AM
Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...


> Somebody on the list I'd bet, know the answer to this.
>
>
> Ok, I think I get it now. Either vinegar or Sodium Silicate in slip, for
> joining clay, acts as a dufloculant, so that there is "more clay" in the
> slip than if a defloc was not used. Hence stronger joints. Is that it?
> Anybody? But some one suggested to me that Sodium Silicate has its
> own "adhesive" properties in clay slip, and might provide an even stronger
> joint. Is this so?
>
> Leland Hall
> Before The Wheel Enterprises
> La Pine, OR USA
>
> On Mon, 25 Nov 2002 21:25:37 -0600, Tommy Humphries
> wrote:
>
> >I think they work about the same, vinegar is just a lot cheaper and
easier
> >to get
> >
> >Tommy
> >
> >
> >----- Original Message -----
> >From: "Leland G. Hall"
> >To:
> >Sent: Monday, November 25, 2002 12:08 AM
> >Subject: Re: HOW TO KEEP GOBLETS FROM SEPERATING...
> >
> >
> >> Hi Tommy. >
> >> I was shown to use a bit of sodium silicate in slip for joining. How
> does
> >> vinegar work? And why? Would one be better than the other? Thanks.
> >>
> >> Leland Hall
> >> Before The Wheel Enterprises
> >> La Pine, Oregon, USA
> >>
> >>
>
>___________________________________________________________________________
> _
> >__
> >> 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.
> >>
> >
>
>___________________________________________________________________________
> ___
> >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.
>
>
____________________________________________________________________________
__
> 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.

vince pitelka on tue 26 nov 02


> Ok, I think I get it now. Either vinegar or Sodium Silicate in slip, for
> joining clay, acts as a dufloculant, so that there is "more clay" in the
> slip than if a defloc was not used. Hence stronger joints. Is that it?
> Anybody? But some one suggested to me that Sodium Silicate has its
> own "adhesive" properties in clay slip, and might provide an even stronger
> joint. Is this so?

Leland -
Actually, they work for completely opposite reasons. Sodium silicate is a
deflocculant, while vinegar is a flocculant. Sodium silicate allows a
slurry with far less water, while vinegar makes the particles attract
one-another more aggressively, making a slip with better adhesive
properties.
- Vince

Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/

John Kimpton Dellow on thu 28 nov 02


Also vince vinegar is a wetting agent .


vince pitelka wrote:
>
> > Ok, I think I get it now. Either vinegar or Sodium Silicate in slip, for
> > joining clay, acts as a dufloculant, so that there is "more clay" in the
> > slip than if a defloc was not used. Hence stronger joints. Is that it?
> > Anybody? But some one suggested to me that Sodium Silicate has its
> > own "adhesive" properties in clay slip, and might provide an even stronger
> > joint. Is this so?
>
> Leland -
> Actually, they work for completely opposite reasons. Sodium silicate is a
> deflocculant, while vinegar is a flocculant. Sodium silicate allows a
> slurry with far less water, while vinegar makes the particles attract
> one-another more aggressively, making a slip with better adhesive
> properties.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> Home - vpitelka@dtccom.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> http://iweb.tntech.edu/wpitelka/
>
> ______________________________________________________________________________
> 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.

--

John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/

Donald Goldsobel on thu 28 nov 02


. .The foolproof method I use is vinegar, not vinegar in slip, on a well
scored surface. I apply the vinegar with a small brush dipped in vinegar
poured into a bottle cap. This is a never fail sysem. If the joint needs
support add a coil of clay and stick in place with scoring and vinegar.

Donald in the Sna Fernando Valley where it is in the 70s, sunny and clear
sky. A day to be thankful for .(Pardon the preposition at the end of the
sentence)
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
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>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

John Rodgers on thu 28 nov 02


Sodium Silicate, which is known as a deflocculant, is an ionizing
compound. When dissolved in water, it's components charge the particles
in the clay slip, causing them repel one another, thereby reducing its
viscosity with out the addition of water. More water in the slip, while
making it more fluid, will also weaken the clay bond between parts,
partly because of the amount of shrinkage that takes place as the water
evaporates. The silicate will not do that.

Slip casters work with this situation all the time, and know that the
viscosity for the best casting is adjusted not with water, but with
sodium silicate. The density of slip must first be adjusted to the
correct value, then the viscosity must be adjusted for the best flow in
casting. The goal in slip casting is for the slip to have a consistency
like heavy cream (water adjustment) , and viscosity like heavy cream
(silicate adjustment). For a given clay body, the numbers are specific,
but each operator must set up that clay body for him/her-self and the
specific application.

To test, typically a given volume of slip is weighed, and compared to
the weight of water of an equal volume, an expression of density.
Old-timers like myself used to know that as specific gravity but today
it's more often simply referred to as density. The density is adjusted
by the addition of water. If an over-the-top amount of water is already
present then more clay must be added.Otherwise adjust with the addition
of water. Once the density is correct, flow rate of the slip is
determined by timing the rate a specific volume of slip runs through a
calibrated orifice. These flow rate gages can be purchased from various
clay supply houses. If the flow is to slow a tiny amount of silicate may
be added. In small batches it is added drop by drop. Larger batches are
adjusted 50 ml at a time. And the silicate is always mixed 50/50 with
water before adding to the slip. Now charged particles in the clay will
repel each other making the slip more fluid (reduced viscosity) without
the addition of water.

There is a caution, addition of to much silicate is as bad as to little.
Both scenarios results in a slip that cannot be poured or cast. A plot
of viscosity vs. silicate would appear as a "U" shaped curve with the
ideal being some where near the bottom center.

When working with solid body pottery clays, the principles still apply.
Water to adjust density, silicate to adjust viscosity. Though with small
quantities of clay such as might be used for bonding the bowl and stem
on goblets, it gets down to a guess as to how much of each to use to get
the best bond. Experience will tell in the end.

My two -

John Rodgers
Birmingham, AL