Richard White on mon 14 aug 06
John and Ron, I have found your book and program to be an extraordinary
reference, and am now progressing from the intellectual understanding (so
far as I can) of glazes learn from your book to the practical, as my wife
and I start to work on our own outside of the classroom setting. We mixed
some small batches of your bases with a few of the variations described in
the book to put on a bunch of small test tiles of the clays we like. Most
worked within expectations (or failed in ways that I think I can attribute
to my own errors in application) except one. I was interested to see in the
book (p 100-101) how the zinc base progressively changed color through
various shades of blue with successive increases in the rutile and no other
change (i.e., all have 1% cobalt plus the rutile), but at 6% rutile it went
from blue to green. However, when I mixed up my batch, I didn't get anything
near green, just a slightly lighter blue than the Light Stormy. What do you
think I did "wrong" (or perhaps I should say, what would you suggest I try
next to achieve a result closer to your picture)?
Dick White
[a neurotic is one who keeps doing the same thing again and again, expecting
a different result... sort of like me with my clay work...]
John Hesselberth on wed 16 aug 06
On Aug 14, 2006, at 9:42 PM, Richard White wrote:
> I was interested to see in the
> book (p 100-101) how the zinc base progressively changed color through
> various shades of blue with successive increases in the rutile and
> no other
> change (i.e., all have 1% cobalt plus the rutile), but at 6% rutile
> it went
> from blue to green. However, when I mixed up my batch, I didn't get
> anything
> near green, just a slightly lighter blue than the Light Stormy.
> What do you
> think I did "wrong" (or perhaps I should say, what would you
> suggest I try
> next to achieve a result closer to your picture)?
Hi Dick,
I'm glad you are enjoying the book and the software and finding them
useful.
The shift from blue to green in the zinc base is highly dependent on
the type and amount of rutile that you have. I used one called Dark
Rutile, but other grades can work--just at a different (usually
higher) rutile level. I would run a line blend with your rutile up to
about 10% and see if the shift occurs somewhere in the range of 5-10.
If that doesn't work, try the same thing with titanium dioxide
instead of rutile. And if that fails see if you can get some "dark
rutile".
Regards,
John
Richard White on fri 18 aug 06
John and Ron, thanks for your replies here and off-list. I had heard
whispers of rutile's fickle nature, and now I too can say she's given me
the run-around. ;-) I adjusted my test mix and we'll see what happens when
I fire again over the weekend. The rutile I have is just whatever they had
at the local supply house; I've got a couple pounds of it so I'll just work
with it and see what happens. If it's the titanium content that causes the
color shift while the other "impurities" cause interesting effects in the
glaze generally, I can try adding a smidge of pure TO2 in lieu of loading
in too much additional rutile... right?
Thanks again.
dw
Ron Roy on sun 20 aug 06
Hi Richard,
You may find combinations of TiO2 and iron to be an answer here. The
definition of Rutile is some thing like between 10 and 5 % iron and the
rest is TiO2 -
Try a line blend of 5% iron and 95% TiO2 in glaze #1 to replce the rutile
and 10% iron and 90% TiO2 in glaze #5.
Then a simple line blend (by volume) equal parts of glaze #1 and #5 = #3,
equal parts of 1 and 3 = 2, 3 and 5 gives #4.
At least you will find out about what role iron has in that glaze.
RR
>John and Ron, thanks for your replies here and off-list. I had heard
>whispers of rutile's fickle nature, and now I too can say she's given me
>the run-around. ;-) I adjusted my test mix and we'll see what happens when
>I fire again over the weekend. The rutile I have is just whatever they had
>at the local supply house; I've got a couple pounds of it so I'll just work
>with it and see what happens. If it's the titanium content that causes the
>color shift while the other "impurities" cause interesting effects in the
>glaze generally, I can try adding a smidge of pure TO2 in lieu of loading
>in too much additional rutile... right?
>
>Thanks again.
>dw
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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