Ivor on thu 9 sep 04
This question may be more complex than it appears.
If we have always weighed out (wet) material then that is what we
should continue to use. If the recipe works then don't change it.
The authors of published glazes may also have been using wet
materials. If their recipes work for you , why change?
We may have been assuming that the material is dry when using
the Seger formula, so our unitary formula is spurious.
But if the glaze works why change?
Ivor
Ivor J Townshend
Macclesfield UK
David Hewitt on fri 10 sep 04
In message , Ivor writes
>This question may be more complex than it appears.
>
>If we have always weighed out (wet) material then that is what we
>should continue to use. If the recipe works then don't change it.
>The authors of published glazes may also have been using wet
>materials. If their recipes work for you , why change?
Yes Ivor, that is exactly what I do. I take the material as supplied and
weigh the amount in the recipe. So long as there is reasonable
consistency of supply there should be no problem for me. However when I
give out a recipe it is for the materials that I use and in the case of
Quartz it could be some 10% to 12% moisture. My glaze program, however,
does not take this into account if I then give an analysis.
One thing I do not wish to do is dry out my quartz and Cornish stone
before weighing it. This seems to me to be a quite unnecessary waste of
time and effort. It is only a problem if the recipe is being used by
someone else whose quartz and Cornish stone does not contain any
moisture.
It would be interesting to know, therefore, if the same moisture
contents apply in other countries. As the reason is for the health
benefit of the user I would be surprised if it only applied in the UK.
Whatever the answer to that question there is also the question of
whether or not glaze programs should take this into account by showing
the raw material analysis for quartz/flint/silica and Cornish stone as
having the appropriate weight of moisture as LOI. Any views would be
appreciated. I am not aware of the question arising with other raw
materials. Is this correct, please?
David
>
>We may have been assuming that the material is dry when using
>the Seger formula, so our unitary formula is spurious.
>
>But if the glaze works why change?
>
>Ivor
>Ivor J Townshend
>Macclesfield UK
--
David Hewitt
Web:- http://www.dhpot.demon.co.uk
John Britt on fri 10 sep 04
David,
I don=92t believe that ceramic materials need to be, nor or can they be,
approached with that degree of scientific precision. Water is lost in
transport and storage to arid regions and some materials are deliquescent,
they absorb water in storage and transport. (Like zinc oxide and gerstley
borate, borax, etc.) These are unknowable variations.
That sort of precision would require scales that were kept in glass cases
not dropped on the floor, not banged around. It would require that potters
zeroed the scale regularly and cleaned off the triple beam and plate after
spilling dry materials on it, etc. It would require that when weighing in
a plastic bucket they wiped out all the dry materials that stuck in the
scrape marks. After it was cleaned, they would have to get all the
moisture in the bucket out, etc.
This is just not happening in a working potters shop.
That is not to mention the mixing stage when water is added and the dust
rises up, which is lost materials that was precisely weighed out which is
now in your lungs or dust mask, not to mention the splashing and stuff
left in the sieve and brushes, etc.
If glaze mixing were that precise no one could have reproduced any glazes
so far and everyone would quit making their own glazes.
Just the variability of the material in the individual bags compared to
the =93average=94 of the percent analysis sheets we are given overrides any
worries about moisture variation.
Just my opinion,
John Britt
www.johnbrittpottery.com
Dorothy Feibleman on fri 10 sep 04
Dear Everyone,
I don`t know if anyone saw my other message about drying out material if
you don`t have a machine that will help you calculate the percent of water
in a material.
Your relaxed attitude to the water can be make a big difference in an
excellent responsive stable porcelain body where you want consistancy.
I made a clay body a couple of years ago that is all of the above. It can
be in long firings but fires in one hour to 1220 in a tunnel kiln and has a
good surface and remains stable in both types of firing. It is much more
translucent than Southern ice, more stable, 100 times nicer to handle etc.
and it does come down to being pretty damn precise in dry weight, how to
mix it etc.
I am a bit surprised with all the glaze calculation programs etc that when
it comes to water content, you have all gone suddenly casual. Or maybe you
are not making product which needs consistancy?
Best,
D
John Britt on fri 10 sep 04
D,
Can you explain more about how you did that and the recipe?
Thanks,
John Britt
www.johnbrittpottery.com
Ron Roy on sat 11 sep 04
Hi Ivor,
Another reason why glaze formulas do not travel well?
Ivor - do you know how the trials are done by those who make up phase
diagrams? Are the materials held at temperature for a long time? Are the
results based on first melting or remelting?
RR
>This question may be more complex than it appears.
>
>If we have always weighed out (wet) material then that is what we
>should continue to use. If the recipe works then don't change it.
>
>The authors of published glazes may also have been using wet
>materials. If their recipes work for you , why change?
>
>We may have been assuming that the material is dry when using
>the Seger formula, so our unitary formula is spurious.
>
>But if the glaze works why change?
>
>Ivor
>Ivor J Townshend
>Macclesfield UK
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 12 sep 04
Hello David,
I'm not sure how to figure out the right number - I do know it can be done
- but any glaze program that can deal with LOI can use the right number to
represent the water in any material.
The loss of water would be counted the same as any other water lost during
the firing process - except of course in this case it would be lost as the
glaze dries on the pot.
I seem to get some sort of thrill when I can trick a glaze program into
doing something it was not designed to do.
I have never received any but dry material in North America except Cornish
Stone - which is imported from the UK.
If we are to exchange recipes then we should at least say if the materials
are wet or dry then - why not. The great problem will be how consistent the
amount of added water is.
It will certainly make a difference with some glazes.
I would think it best to assume the materials are dry unless stated as wet.
RR
>Yes Ivor, that is exactly what I do. I take the material as supplied and
>weigh the amount in the recipe. So long as there is reasonable
>consistency of supply there should be no problem for me. However when I
>give out a recipe it is for the materials that I use and in the case of
>Quartz it could be some 10% to 12% moisture. My glaze program, however,
>does not take this into account if I then give an analysis.
>
>One thing I do not wish to do is dry out my quartz and Cornish stone
>before weighing it. This seems to me to be a quite unnecessary waste of
>time and effort. It is only a problem if the recipe is being used by
>someone else whose quartz and Cornish stone does not contain any
>moisture.
>
>It would be interesting to know, therefore, if the same moisture
>contents apply in other countries. As the reason is for the health
>benefit of the user I would be surprised if it only applied in the UK.
>
>Whatever the answer to that question there is also the question of
>whether or not glaze programs should take this into account by showing
>the raw material analysis for quartz/flint/silica and Cornish stone as
>having the appropriate weight of moisture as LOI. Any views would be
>appreciated. I am not aware of the question arising with other raw
>materials. Is this correct, please?
>
>David
>>
>>We may have been assuming that the material is dry when using
>>the Seger formula, so our unitary formula is spurious.
>>
>>But if the glaze works why change?
>>
>>Ivor
>>Ivor J Townshend
>>Macclesfield UK
>
>--
>David Hewitt
>
>Web:- http://www.dhpot.demon.co.uk
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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