Dewitt on sat 24 nov 01
Also, checkout http://digitalfire.com/education/glaze/unlabel.htm
deg
At 15:22 11/24/01 -0700, you wrote:
>Well, Cat.
>
>Sounds like a major hassle. I would start with
>process of elimination. Are any of the newly mixed
>glazes okay? Do they omit materials common to the
>bad glazes? You might do some 100 gram batches
>with glazes which contain different ingredients.
>Another thing you might consider is testing known
>ingredients' characteristics vs the
>characteristics (weight, consistency, reaction to
>mixing with water, reaction to firing, appearance,
>etc.) of the suspect ingredients.
>
>I don't know about the lab testing. It may or may
>not be expensive, and I'm sure others will have
>advice for you. Perhaps the chemistry dept. would
>be interested in helping you out with this
>challenge.
>
>Good luck,
>
>Cindy Strnad
>Earthen Vessels Pottery
>RR 1, Box 51
>Custer, SD 57730
>USA
>cindy@earthen-vessels-pottery.com
>http://www.earthen-vessels-pottery.com
>
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---------------------------
Dewitt Gimblet
dewitt@texas.net
Austin, TX
---------------------------
Snail Scott on sat 24 nov 01
>...someone put a bag in the wrong place in the storage room but
>have no idea which ingredient is corrupt.
Could you just do fusion tests of each thing? At least you
could see if they're close to what they should be, pretty
cheaply and easily. If you don't have any 'pure' samples
for comparison, maybe you could borrow a bit from local
potters? "Hi, neighbor! can I borrow a teaspoon of silica?"
If the test melts don't turn up a discrepancy, you can then
turn to commercial testing, but surely if the difference
is evident in the fired glazes, with only a partial amount
of the contaminated material, it ought to show up in a
melted test button.
-Snail
Cat Audette on sat 24 nov 01
Hi again
Here at my University we have a big problem. They store their glaze chemicals in huge containers, several bags per. This semester the glazes are
going bad. They look and smell wrong and are not performing at all. We realized that someone put a bag in the wrong place in the storage room but
have no idea which ingredient is corrupt.
With thousands of pounds of materials and trash-can size buckets of glazes gone bad, this is a very expensive mistake.
Is there any way we can send samples of the materials out to be tested? and to where? Will it be expensive? Are there any alternatives to doing this?
We want to throwing things out...
Any suggestions would be appreciated.
Happy Holidays.
Cat Audette
cataudette@earthlink
Cindy Strnad on sat 24 nov 01
Well, Cat.
Sounds like a major hassle. I would start with
process of elimination. Are any of the newly mixed
glazes okay? Do they omit materials common to the
bad glazes? You might do some 100 gram batches
with glazes which contain different ingredients.
Another thing you might consider is testing known
ingredients' characteristics vs the
characteristics (weight, consistency, reaction to
mixing with water, reaction to firing, appearance,
etc.) of the suspect ingredients.
I don't know about the lab testing. It may or may
not be expensive, and I'm sure others will have
advice for you. Perhaps the chemistry dept. would
be interested in helping you out with this
challenge.
Good luck,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
David Hewitt on sun 25 nov 01
A few years ago now, Mike Bailey and I did a series of tests on
different materials to answer the question of 'Those unlabelled Bags and
Buckets'.
This included button tests, LOI, Underglaze colour tests and Bulk
Density tests. All things that any potter could undertake, but avoiding
the cost of actually having a material analysed. While not full proof it
does help to sort out a lot of queries.
This work was published in Ceramic Review at the time, but is available
on my web site under 'Unlabelled Bags & Buckets'
http://www.dhpot.demon.co.uk
David
In message , Cat Audette writes
>Hi again
>
>Here at my University we have a big problem. They store their glaze chemi=
>cals in huge containers, several bags per. This semester the glazes are
>going bad. They look and smell wrong and are not performing at all. We re=
>alized that someone put a bag in the wrong place in the storage room but
>have no idea which ingredient is corrupt.
>
>With thousands of pounds of materials and trash-can size buckets of glaze=
>s gone bad, this is a very expensive mistake.
>
>Is there any way we can send samples of the materials out to be tested? a=
>nd to where? Will it be expensive? Are there any alternatives to doing th=
>is?
>We want to throwing things out...
>
>Any suggestions would be appreciated.
>
>Happy Holidays.
>Cat Audette
>cataudette@earthlink
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
Ceramic Design Group on sun 25 nov 01
Someone had mentioned a "process of elimination" testing on your chemicals.
This may be a correct start, empirically, but seriously, I think that it
looks good only on paper.
Lets assume that your large container of Custer Feldspar was indeed
contaminated with whiting, dolomite, or whatever other whitish powder. We
need to think how these bulk powders intermix with each other when a scoop
of the wrong material is put back into the bin on top of Custer Spar. The
physical action of powder A mixing with powder B doesn't translate that
there is just a layer of the wrong material sitting nicely on top of the
Cuuster Spar. It becomes co-mingled and each time you scoop into the
offending materials, they are further mixed together, randomly. There are
other physical actions that can also occur and I am sure that there are
those with more of a scientific explanation on the list that can describe
the mixing of bulk powders better than I.
I would think that you could do all the testing in the world and still not
come up with information that would without a doubt, identify properly the
materials in question.
What I would do is the more radical thing, and get rid of the materials and
start fresh. Glaze chemicals are relatively reasonable in cost, (with a few
exceptions such as cobalt, tin, etc.) in cost and would it not make sense to
replace them rather than spending countless hours of valuable time trying to
figure out which materials have been contaminated? And not to mention the
countless number of glazes mixed for testing, pots glazed and tested? Why
struggle?
We have a very good methodology in our plant for mixing bulk glazes in
quantities of 10-40 gallons. Even though this system works, there are times
when staff has a nagging thought that "perhaps I didn't add this, or I did,
or was it really F-4 spar that I added?" Whatever that doubt may be, if it
exists, I suggest, not just suggest, but throw the partially mixed glaze
out. I would rather pay a few more hours of labor to mix the glaze again,
correctly and whatever the materials costs, then to have a kiln load of
seconds and not satisfy our clients needs.
It seems that the prudent course of action would be to replace the
materials. IMHO.
Jonathan
--
Jonathan Kaplan
CERAMIC DESIGN GROUP
PO Box 775112
Steamboat Springs, CO 80577
(970) 879-9139
info@ceramicdesigngroup.net
www.ceramicdesigngroup.net
Michael Wendt on sun 25 nov 01
To All:
This event explains why I never repackage materials from the original
containers. Once the bag is gone, you have a white , gray or black powder. I
once got a bag of cobalt oxide from Westwood ceramic supply and guess what,
it was manganese dioxide, not cobalt oxide. They replaced it on my say so
and the new cobalt actually produced blue.
The people who wrote in to say what kind of storage containers should be
used were not wrong, but in many settings, the chances for mix-ups mean
original bags are the best.
On a similar note, I have a rule here that unknown materials are thrown
away. Don't be "penny wise and pound foolish", as they say.
Regards,
Michael Wendt wendtpot@lewiston.com
Cat wrote:Here at my University we have a big problem. They store their
glaze chemicals in huge containers, several bags per. This semester the
glazes are
going bad. They look and smell wrong and are not performing at all. We
realized that someone put a bag in the wrong place in the storage room but
have no idea which ingredient is corrupt.
With thousands of pounds of materials and trash-can size buckets of glazes
gone bad, this is a very expensive mistake.
Ceramic Design Group on sun 25 nov 01
Another take on this event is a procedure that we use in our facility.
We have, essentially 3 systems for storage of materials.
The first system are 2 quart RubberMaid lidded containers that are
alphabetically arranged on shelves above our working table. These hold each
and every one of the materials that we use in the shop including colorants.
These containers can hold up to 3 pounds or so of materials. We use these
for weighing out tests. Each container is labeled legibly. We also have
small 4" cylindrical containers with screw on lids for all our Mason stains.
This size, again, is used for testing. They are also labeled with the stain
number as well as the stain name. Our bulk 10 pound drums of stain are used
for mixing large batches. To avoid any contamination of materials, the shop
rule is to have only one container open at one time. That is the material
being weighed and being used.
The second system are 5 gallon containers with lids that are stored
underneath the working table. These only contain materials that we use on a
day to day, very common basis such as spars, flint, whiting, dolomite, EPK,
frits, etc. The outside of the container is labeled, as is the lid. We cut
out the bag label and put it inside the container. I instruct staff, as well
as take heed myself, that it is only necessary to have one container out and
opened at the same time. If the container is open, it means someone is
working with it. If it is closed, it belongs under the table. These 5 gallon
containers are used when mixing up to 13,000 grams, which is more or less
the volume of dry ingredients necessary to make approximately 5 gallons of
glaze.
The third system is the bag, usually 50 pounds. When we are making large
batches of glaze bigger than 5 gallons, we go to the pallet racks of stored
bags of materials and bring over a full bag, depending on the quantity
needed. Any extra left in the bag is put into the 5 gallon containers.
We have all our shop glazes as well as client glazes printed out in both
Hyperglaze and Insight formats, each glaze in a clear plastic protector. The
Hyperglaze format has the total batch weight for the particular glaze, eg,
if we need 30 gallons of glaze, it is calculated on that basis. These are
all bound in a 3 ring binder. It is very easy to use a wax pencil/china
marker to cross off ingredients or extend them out as needed. Using
different colors can be of advantage also to indicate anything you wish on
the clear plastic sheet protectors. These markings are easily removed with a
paper towel when the batch is finished.
I think its important to have a procedure for glaze mixing. I've screwed up
alot of glazes in my history because I didn't have a procedure. Its
especially important when staff is involved, and I would think important
also in an academic situtation, whcih I know, has different parameters, none
of which can protect anyone or anything from stupidity.
Jonathan
--
Jonathan Kaplan
CERAMIC DESIGN GROUP
PO Box 775112
Steamboat Springs, CO 80577
(970) 879-9139
info@ceramicdesigngroup.net
www.ceramicdesigngroup.net
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