Gary Harvey on tue 18 jan 05
Has anyone out there tested the COE of Laguna's B mix 5 ? I have not =
been able to obtain this information from the Laguna company. Yes I =
looked on their website and even emailed them do no avail. GH Palestine =
TX
Marvin Klotz on tue 18 jan 05
If anyone has I'd sure like that information too. I once asked Jon Pancini
about that also and he told me that they didn't give out that information
because the COE was dependent on various things such as how you fired
etc. Since I'm a total ignoramous that quieted me right down and I went
back to blind trials trying to find a clear glaze that wouldn't craze on my
Cone 5 B mix work. If anyone has such a glaze recipe I'd sure appreciate
that too tho I don't have much to offer in return, as I said I'm an
ignoramous. I do know that glazes that rvrntually craze on the straight B
mix craze even faster on the cone 5 B mix with grog.
Joan Klotz
At 03:25 PM 1/18/2005, you wrote:
>Has anyone out there tested the COE of Laguna's B mix 5 ? I have not been
>able to obtain this information from the Laguna company. Yes I looked on
>their website and even emailed them do no avail. GH Palestine TX
>
>______________________________________________________________________________
Michael Wendt on wed 19 jan 05
Joan,
Try making 2" diameter rings about 3/4" tall and as thin as you can throw
them. Glaze the inside of the ring with the trial glazes. I use a Dremel
with a diamond saw to cut most of the way through the ring after firing and
then tap the junction lightly to crack it. Crazed glazes keep the ring's
crack tightly closed while glazes that are under compression will open the
crack slightly. It is cheaper and better than a dilatometer since it works
with your glazes and clay in your kiln using your firing cycle, applied
thickness and all the other variables that affect crazing.
Good Luck,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Charles Moore on wed 19 jan 05
----- Original Message -----
From: "Marvin Klotz"
I went
> back to blind trials trying to find a clear glaze that wouldn't craze on
> my
> Cone 5 B mix work. If anyone has such a glaze recipe I'd sure appreciate
> that too tho I don't have much to offer in return, as I said I'm an
> ignoramous. I do know that glazes that rvrntually craze on the straight B
> mix craze even faster on the cone 5 B mix with grog.
>
> Joan Klotz
Hi, Marvin, I have had very good luck with Ron and John's Glossy Base #2 (in
MC6G) with and without colorants and have used it on B Mix-5 with grog
successfully.
Charles Moore
Sacramento
Jon Pacini on wed 19 jan 05
Greetings All---
About a year or so ago I started doing comprehensive COE testing of all the
Laguna Clays in preparation to publish that Information. You can find that
post in the achieves if you need the exact date.
As Joan mentioned there are a lot of factors that go into the COE of a clay.
The time and temperature involved in the firing have an enormous effect on
the physical COE of a clay. So what I get for lab COE numbers is subject to
variations due to those conditions and the likelihood of you getting the
exact same number from a sample fired in your kiln is about the same as the
odds on a coin flip.
But because we get so many calls for COEs and many potters feel ballpark
numbers are better than none at all, I ve gone ahead and done them for
anyone who is interested in them. The list isn t complete yet, but I hope to
have them on the Web site soon and we may be ready with a complete list of
both Eastern and Western clays at NCECA.
The COE I have for WC 401 is 5.74 x 10 6. This sample was fired in a Skutt
818-3 to Orton Standard cone 5 bent over in a nice U shaped arch with the
tip just touching the shelf. It was ramped at 250* per hr to 1000*F, then
350* F per hr. to 2100*f, then 30* F per hr. to 2160*f with no soak.
Best regards
Jon Pacini
Clay Manager
Laguna Clay Co
Ron Roy on wed 19 jan 05
Hi Gary,
I will dil it if you care to make and fire a sample - there are others who
will be interested.
RR
>Has anyone out there tested the COE of Laguna's B mix 5 ? I have not been
>able to obtain this information from the Laguna company. Yes I looked on
>their website and even emailed them do no avail. GH Palestine TX
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ivor and Olive Lewis on thu 20 jan 05
Dear Joan Klotz,
I only know of one solution to your problem. That is to do the hard
yards with test pieces and incremental changes within a set group of
suitable compounds. This may involve several firings and give
disappointing results to begin with.
The reasons are clear cut and simple. Natural materials which we use
to formulate both clay mixes or particular pottery bodies and glazes
are variable. Jon Pacini and Ron Roy are people who know this and
understand how to keep their products within acceptable ranges of
variability, which is good commercial and competitive practice. But
they cannot make a universal clay body that will work with every glaze
variation possible and guarantee success under all firing conditions
in every kiln.
Even if you know the theoretical values for all of the ingredients you
use to compound your glazes, you can only calculate a theoretical
answer. Even if you paid Ron Roy to find the C of E of you clay you
would be no further forward without a similar practical test on the
glaze you get, if someone lends you a recipe, because the two may be
incompatible.
Doing tests to solve this problem is relatively simple if you can
select materials, weigh, count and mix. It has one draw back. It takes
a fair amount of time. It also needs a clear head because it is based
on logical arguments, sound pragmatic judgements and a basic knowledge
of raw materials.
If you wish to know more please contact me Off List.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Marvin Klotz on thu 20 jan 05
Thank you Ivor for your input on this topic. Unfortunately I do not have
the time, the facilities or the equipment to personally investigate this
problem with glaze fit to the degree that you advise. There is another
solution. One of the reasons I value Clayart is that it allows one to
benefit from the experience of others who have had similar problems - a
pooling of efforts. As a result of my posting, re the difficulty in
finding a suitable clear glaze for Laguna's B5, I have received two useful
postings from fellow Clayarters, and I thank them. Also, you probably saw
the note from Jon Pacini indicating that he is investigating the COEs of
the Laguna clay bodies and that the results of his investigations will be
available sometime in the future. Thank you Jon. I'm sure that such
information will be useful to many of us. It will allow for a directed
search for a suitable alternative clay body when one has a favorite glaze
that doesn't quite fit the clay body in use, for example. At no time did I
indicate that I expected a universal clay body that will work with all glazes.
Perhaps it was unintended but there was just a hint of patronage in your
final paragraph. Although not a glaze chemist, I believe that I do have a
clear enough head to follow logical arguments, make pragmatic judgements
and have some basic knowledge of raw materials. Also I have spent some
time carrying out tests in an attempt to solve the problem - with some
small success. Alas I am an amateur potter with limits on the time I can
spend on this,
Best Regards,
Joan Klotz.
At 07:09 PM 1/19/2005, you wrote:
>Dear Joan Klotz,
>I only know of one solution to your problem. That is to do the hard
>yards with test pieces and incremental changes within a set group of
>suitable compounds. This may involve several firings and give
>disappointing results to begin with.
>snip
> But they cannot make a universal clay body that will work with every glaze
>variation possible and guarantee success under all firing conditions
>in every kiln.
>
>snip
>Doing tests to solve this problem is relatively simple if you can
>select materials, weigh, count and mix. It has one draw back. It takes
>a fair amount of time. It also needs a clear head because it is based
>on logical arguments, sound pragmatic judgements and a basic knowledge
>of raw materials.
>
>Ivor Lewis.
>Redhill,
>S. Australia.
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
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>
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>melpots@pclink.com.
Ron Roy on fri 21 jan 05
Hi Michael,
Cheaper and better in some ways but not in other ways.
The information on free quartz and cristobalite in bodies is not there and
it can be an important part of solving fit problems.
The melting point, transition stage and set points of glazes is gotten from
dilatometery - again - valuable information when solving fit problems.
There is no better tool than dilatometry for designing clay bodies -
especially when ideal glaze expansion factors are taken into account.
I like the idea of rings to guage comparitive COE's of clays and glazes but
- getting the clay and glaze the same thickness each time is problematic.
I am not saying it is not a good thing for potters to do - and encourage
all potters to do it on a regular basis - the bigger the ring the better
from my point of view - but certainly not "better" then dilatometry.
RR
>Try making 2" diameter rings about 3/4" tall and as thin as you can throw
>them. Glaze the inside of the ring with the trial glazes. I use a Dremel
>with a diamond saw to cut most of the way through the ring after firing and
>then tap the junction lightly to crack it. Crazed glazes keep the ring's
>crack tightly closed while glazes that are under compression will open the
>crack slightly. It is cheaper and better than a dilatometer since it works
>with your glazes and clay in your kiln using your firing cycle, applied
>thickness and all the other variables that affect crazing.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Michael Wendt on fri 21 jan 05
Dear Ron,
You are right. My choice of words was poor. The ring method is just so low
tech , cheap and immediate.
Most of our problems with clay-glaze interactions come from the lack of
empirical data we all suffer from ( you have the dilatometer so you have
that added info) :-)
The rings work well when you have a dark glaze that makes crazing harder to
see. They might make it easier for people to fine tune fit without
overshooting their goal.
I stand corrected.
And Thanks,
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
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