Don Kopyscinski on mon 8 jul 96
Hi everyone,
On July 5th Janice Strawder wrote:
>Within the past year I have experienced two episodes of "bad frit".<
and
>I have been keeping track of Frit Batch numbers, taken from the individual
bags, and have identified "good" bags from "bad" bags". After the first
episode, I was relieved to find successive good bags, but since the problem has
reoccured, I 'm finding it frustrating, and am considering switching to other
manufacturers of frit.<
One day when I was in the midst of a terrible raw materials problem, and had
been intentionally sent up a blind alley by my supplier to cover their ass (not
that I'm bitter), I may have run into the cause of this problem. I went to
Brooklyn, NY to visit with Mitch Kaufman of Jack D. Wolfe Co. to brainstorm on
solving my problem. I brought with me nearly 1000 test tiles to show where I had
been, and where I was stuck. While waiting for Mitch to meet with me, I observed
him inspecting some tiles. They were 4X4 tiles that had been covered with a
black underglaze and glazed with a frit and fired. Mitch was inspecting the
final result and I believe doing a bubble count on a measured area. When I asked
him what he was doing and why, he explained that although the major frit makers
denied the practice, he was pretty sure that they were using continuous batch
furnaces to make the frits. He had seen variations in the frits and had
attributed it to the fact that the makers, when changing from one batch to
another, would use the next batch to push the first one out. Someone then
decided where one frit batch began, and another ended (much as our suppliers do
when mixing clay and using one batch to push the previous one out, you may have
at one time or another noticed a swirl of another clay in your pug). He had
requested a "middle of the run" and I think was offering to buy a whole batch,
if they would ensure that he didn't get the two suspect "ends" to insure
uniformity. He apparently had somehow developed a baseline (again I think it was
determined by bubble population in a fixed area of tile on which the frit had
been applied over a black underglaze to improve contrast and better view the
bubbles) that he could use to proof new batches before he committed them to
production (of glazes I think). I gained a lot of respect for Mitch that day,
and was pleased to know that there are people out there who double check that
what they got, is what they were told was sent.
>I have been keeping track of Frit Batch numbers, taken from the individual
bags, and have identified "good" bags from "bad" bags". After the first
episode, I was relieved to find successive good bags, but since the problem has
reoccured, I 'm finding it frustrating,<
Years ago I came across several funky batches of Gerstley Borate. Finally.....
one batch came through that did what I wanted it to do. I bought 250 lbs.
(enough for 50 ....fifty pound batches of the glaze I was trying to stabalize
and I'm still happily working off that store today with 125 lbs to go) of that
same lot # after inspecting a "pre-shipment sample". It's the only way to go
with highly variable materials (your frit apparently falls in this
category...anything that comprises 75% of your glaze is a likely candidate to
dramatically show small shifts. I would recommend proofing a particular lot #
for your purpose and then buying all you can get your hands on within reason
(with an assurance from your supplier that your sample and the lot get are one
in the same). Now if Mitch's theory about the beginning and end of a batch being
variable in composition is correct you will still then need to proof the bags
you have in a timely manner to insure that the store you have is all usable for
your intended purpose. Once that is done, you can sleep nights knowing that at
least for a while you've got that problem covered and in the bag. Start to panic
before your store hits bottom, and begin the process again when that time comes.
Another aproach might be to diversify the frit content to minimize the impact of
shifts perhaps using 15% each of 5 similar frits. I would go with the bulk
buying as a first resort to buy some time to work on the alternative if needed.
Any frit makers out there care to comment???
Regards,
Don Kopyscinski
Bear Hills Pottery
Newtown, CT
(Still needing to respond to lots of e-mail......but in deep, the studio filled
with WIP and a new project consuming me ....bear with me)
Louis Howard Katz on tue 9 jul 96
Was glad to hear someone else speaking the praises of buying in quantity
to help eliminate variability. Always frustrated me when customers with
multiple employees would buy enough material to last less than a few
months and then complain about inconsistency in natuarally occuring minerals.
Dave Shaner, known in part by numerous glaze recipes, buys pallets of
feldspar, truckloads of clay, full bags of colorants, even stains he
purchases in quantity.
In trying to track down problems with lime blows I checked individual
bags of materials from truckloads with the same batch numbers. The
variation from one bag to another in the amount of residue on a thirty
mesh screen was large. Being a naturally occuring mineral costing pennys
there was only so much blame I could place on the manufacturer. More
carefull blending and handling could probably near eliminate the
variation but could easily double the price.
Variations in frits, stains, cones, and refined colorants, are more
difficult to justify. We pay big bucks for consistancy in these materials
and should be able to demand it. If side by side tests of these materials
don't fire the same, ask the question if you are using a glaze that is
too sensitive to variation, then change manufacturers.
Louis
***************************************************
*Louis Katz lkatz@falcon.tamucc.edu *
*Texas A&M University Corpus Christi *
*6300 Ocean Drive, Art Department *
*Corpus Christi, Tx 78412 *
*Phone (512) 994-5987 *
**************************************************
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