Autumn Downey on wed 18 feb 98
Is there any information on the expansion of the colouring oxides besides
iron, manganese, Zr and titanium? I realize most are used in pretty small
quantities, except maybe tin and copper, but it would be sort of nice to
know what effect they are having. (Even qualitatively? - low, medium,
high?)
Thanks.
Autumn Downey
downeya@internorth.com
Yellowknife, NWT, Canada
David Hewitt on fri 20 feb 98
Mayer & Havas give the following figures in % Wt. Cubic x10^-7/oC. To
convert to Linear coefficients, divide by 3.
Cr2O3 5.1
CoO 4.4
Fe2O3 4.0
NiO 4.0
MnO 2.2
CuO 2.2
SnO2 2.0
I think the GlazeChem program includes a value for every oxide.
I always like to include the colouring oxides when calculating the
expansion.
David
In message , Autumn Downey writes
>----------------------------Original message----------------------------
>Is there any information on the expansion of the colouring oxides besides
>iron, manganese, Zr and titanium? I realize most are used in pretty small
>quantities, except maybe tin and copper, but it would be sort of nice to
>know what effect they are having. (Even qualitatively? - low, medium,
>high?)
>
>Thanks.
>
>Autumn Downey
>downeya@internorth.com
>Yellowknife, NWT, Canada
>
--
David Hewitt
Ron Roy on fri 20 feb 98
Hi Autumn,
I'm looking at the Hamer Dictionary - page 379 - 4th edition. This is a
great book - as I have said many times - wish I had a copy from the
beginning of my life in clay - would have saved me countless hours in the
maze.
Fe2O3 is between zinc and calcium oxide as are TiO2, NiO
Zirconium and Tin are rated the same - quite low - just above Alumina.
Zirconium silicate should be even lower cause of the combined silica.
Copper oxide is between ZnO and MgO - on the low side.
Cobalt oxide is higher - just below BaO so you could say medium.
This could lead to some misunderstanding however. Lets say a glaze has an
expansion/contraction of 5 when we calculate. Lets say we add a material
with a relatively low expansion but it is above the expansion of the glaze
- say 6 - we will then raise the expansion of the glaze. If we substitute a
lower expanding oxide for a higher one - then we do lower the expansion of
the glaze - well not all the time - because some oxides work differently
according to the amounts present.
We must realize - testing is what tells us for sure - calculation is a
wonderful insight into our glazes but our desire for simple answers can
lead us down the garden path if we aren't careful.
>----------------------------Original message----------------------------
>Is there any information on the expansion of the colouring oxides besides
>iron, manganese, Zr and titanium? I realize most are used in pretty small
>quantities, except maybe tin and copper, but it would be sort of nice to
>know what effect they are having. (Even qualitatively? - low, medium,
>high?)
>
>Thanks.
>
>Autumn Downey
>downeya@internorth.com
>Yellowknife, NWT, Canada
Ron Roy
93 Pegasus trail
Scarborough Otario
Canada M1G 3N8
Phone: 416-439-2621
Fax: 416-438-7849
Web page: Home page http://digitalfire.com/education/people/ronroy.htm
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