vince pitelka on mon 12 feb 01
> I'm curious about something here. I have been able to do this if I use
> equal parts of the oxide (or stain) with ball clay and gerstley borate. I
> thought that the addition of the clay and the flux were what constitutes a
> true underglaze. Is that so, or is anything you put underneath an
> underglaze? What exactly is it about the clay and flux addition that
makes
> it stable?
Gail -
Melinda used pure ochre and water, and that is what I was addressing. If
you make a proper underglaze, it is formulated to stick to the bisque-fired
surface, and to allow over-glazing with no crawling problems. The ball-clay
provides the bonding in application, and the flux insures a good bond in the
melt.
In my experience, I have noticed that underglazes are usually tinted much
more powerfully than engobes (as I use the term - a slip adjusted to fit
bone-dry or bisque-fired wares). Generally, in color and surface an engobe
looks and acts much like a normal slip. An underglaze is often much more
powerfully tinted, and the color will usually come through just about any
glaze. So underglazes can often be applied very thinly and still be quite
effective, and thus they can get away with very simple combinations of
ingredients - as you said, a little ball clay to give a tight coat, and a
little flux to guarantee a good interface in the melt.
Best wishes -
- 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://www.craftcenter.tntech.edu/
Ceramic Design Group on tue 13 feb 01
on 2/12/01 8:35 PM, vince pitelka at vpitelka@DTCCOM.NET wrote:
>> I'm curious about something here. I have been able to do this if I use
>> equal parts of the oxide (or stain) with ball clay and gerstley borate. I
>> thought that the addition of the clay and the flux were what constitutes a
>> true underglaze. Is that so, or is anything you put underneath an
>> underglaze? What exactly is it about the clay and flux addition that
> makes
>> it stable?
>
Underglazes are basically a clay system with colorants, usually commercial
stains that provide consistency from batch to batch. The clay system usually
has a small percentage of flux that will bond the underglaze to the clay
surface beneath it. There are also materials in the undergalze for
brushability (CMC) suspension, etc. etc. Even when a commercial underglazxe
preparation is fired higher then its recommended temperature, the color is
perhaps the only thing that one may notice that changes, and really not that
much, really depending on the glaze that it used over it. The underglaze
preparation is more refractory and can take a wide range of temperatures.
We use Amaco Velvet Underglazes as well as Amaco Liquid Underglazes (LUGs).
WHile these have been traditionally used in low temperature clay/glaze
systems, many of them are useable right up to cone 9-10. We have sprayed
them, dipped them, poured them, brushed them, etc. We have also used them to
color glazes by mixing them into a glaze base, to color casting slips, the
list goes on. One of our current projects is spraying them onto porcelain
plates for a designer in NYC. After spraying them on the greenware, we
bisque them to cone 06, dip them in a clear glaze and fire them to cone 4.
The resulting colors are intense and in your face bright. We get better
glaze coverage and consistency when the underglaze is fired onto the piece
first.
Good Luck
Jonathan
Jonathan Kaplan, president
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139
jdkaplan@cmn.net
info@ceramicdesigngroup.net
Plant Location:
1280 13th Street Unit 13
Steamboat Springs CO 80487
(please use this address for all deliveries via UPS, common carrier, Fed Ex,
etc.)
"Custom design and manufacturing for the ceramic arts, giftware and pottery
industries. Molds, models, and tooling for slip casting, jiggering and
hydraulic pressing. Consultation on technical issues such as clay bodies
glazes, and kilns."
Jonathan
Wade Blocker on wed 14 feb 01
Susan,
The majority of Amaco underglazes come in pints. They are less expensive
than buying those 2 oz containers. Amaco has a nice catalog - free, which
lists all the underglazes and the size in which they are available.I order
from Amaco directly, since most ceramic suppliers only carry the 2 oz
containers. Mia in ABQ
Scsclay@AOL.COM on wed 14 feb 01
Jonathan,
I too use Amaco Velvets, paint and spray, but you also said you dip.
We wanted to dip some tiles once and figured it would take a zillion cases
of those little 2 ounce jars, poured into a container. Only some of the
colors even come in pints. Are you able to get them in gallons? When I called
Amaco, they referred me to Brickyard, and they didn't have them. It would be
nice to be
able to at least get pints in more of the colors.
Also, to Carol who had trouble with the velvets on paperclay-
I use them on both unfired and fired paperclay and have not had that
problem. In fact I did a very large piece with a lot of Chartreuse, the color
you mention. It is my experience that you don't have to fire the paperclay
first.
Thanks,
Susan Schultz
Stonington, Ct.
Jonathan Kaplan on wed 14 feb 01
on 2/14/01 6:18 AM, Scsclay@AOL.COM at Scsclay@AOL.COM wrote:
> Jonathan,
>
> I too use Amaco Velvets, paint and spray, but you also said you dip.
> We wanted to dip some tiles once and figured it would take a zillion cases
> of those little 2 ounce jars, poured into a container. Only some of the
> colors even come in pints. Are you able to get them in gallons? When I called
> Amaco, they referred me to Brickyard, and they didn't have them. It would be
> nice to be
> able to at least get pints in more of the colors.
You can order pints from AMACO in all of the Velvets and Lugs. If you want
larger quantities, the minimum is a 5 gallon pail, and it can only be done
when they are making them so that they can pour off what you need before
they go to fill the other smaller sized containers. You sould be able to
order direct from AMACO. If for some reason you can't, contact me off the
list and we will talk.
--
Jonathan Kaplan
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
jdkaplan@cmn.net
Plant Location (use for all UPS, Common Carrier, and Courier deliveries)
1280 13th Street
Steamboat Springs CO 80487
Rachael Rice on thu 15 feb 01
Bennett Pottery in Florida has a large selection of pint size amaco velvet
underglazes. It is so much cheaper in the 16oz. size (1/2 the cost).
Rachael
Wade Blocker wrote:
> Susan,
> The majority of Amaco underglazes come in pints. They are less expensive
> than buying those 2 oz containers. Amaco has a nice catalog - free, which
> lists all the underglazes and the size in which they are available.I order
> from Amaco directly, since most ceramic suppliers only carry the 2 oz
> containers. Mia in ABQ
>
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