Marley Wolhud on fri 18 sep 98
First everyone thank you for your responses on my sadly disappointing
first firing. It is nice to know that I hopefully just have to make a
few adjustments i.e. thinness of glaze and keep trying.
Secondly, in my quest to understand how glaze colorants work on various
glaze bases I have been reading Robin Hopper's book the Ceramic
Spectrum. I admit I have to read every sentence several times to get
it, but when I was looking at the table titled Ceramic Spectrum a few
things jumped out. He lists various oxides and what kind of glaze base
they work best in to achieve whatever color you want. He seems to list
many oxides working best in lead glazes which I am not interested in.
The other glaze base he seems to refer to most is barium based. My
questions are, is barium based glazes also toxic? and, I haven't seen
any glaze bases yet which are hi barium content. (which leads me to
believe it IS toxic.
Thanks to everyone for your response!
Diane
Ron Roy on sun 20 sep 98
Hi Diane,
There are lots of high Barium content glazes around. They are those that
give the matte turquoise surface when used with copper. Strontium, if
present in high enough quantities also gives that silky matte surface but
not the same colour response.
All glazes leach - the question is how much and how fast. The other
question is - how much is too much - there is a wide difference of opinion
on the subject.
Unless you are willing to have your glazes tested for release it is going
to be difficult to determine what is possibly safe for ware that can be
used to food.
>----------------------------Original message----------------------------
>First everyone thank you for your responses on my sadly disappointing
>first firing. It is nice to know that I hopefully just have to make a
>few adjustments i.e. thinness of glaze and keep trying.
>
>Secondly, in my quest to understand how glaze colorants work on various
>glaze bases I have been reading Robin Hopper's book the Ceramic
>Spectrum. I admit I have to read every sentence several times to get
>it, but when I was looking at the table titled Ceramic Spectrum a few
>things jumped out. He lists various oxides and what kind of glaze base
>they work best in to achieve whatever color you want. He seems to list
>many oxides working best in lead glazes which I am not interested in.
>The other glaze base he seems to refer to most is barium based. My
>questions are, is barium based glazes also toxic? and, I haven't seen
>any glaze bases yet which are hi barium content. (which leads me to
>believe it IS toxic.
>
>Thanks to everyone for your response!
>
>Diane
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Ron Roy on tue 22 sep 98
Hi Diane,
There are lots of high Barium content glazes around. They are those that
give the matte turquoise surface when used with copper. Strontium, if
present in high enough quantities also gives that silky matte surface but
not the same colour response.
All glazes leach - the question is how much and how fast. The other
question is - how much is too much - there is a wide difference of opinion
on the subject.
Unless you are willing to have your glazes tested for release it is going
to be difficult to determine what is possibly safe for ware that can be
used to food.
>----------------------------Original message----------------------------
>First everyone thank you for your responses on my sadly disappointing
>first firing. It is nice to know that I hopefully just have to make a
>few adjustments i.e. thinness of glaze and keep trying.
>
>Secondly, in my quest to understand how glaze colorants work on various
>glaze bases I have been reading Robin Hopper's book the Ceramic
>Spectrum. I admit I have to read every sentence several times to get
>it, but when I was looking at the table titled Ceramic Spectrum a few
>things jumped out. He lists various oxides and what kind of glaze base
>they work best in to achieve whatever color you want. He seems to list
>many oxides working best in lead glazes which I am not interested in.
>The other glaze base he seems to refer to most is barium based. My
>questions are, is barium based glazes also toxic? and, I haven't seen
>any glaze bases yet which are hi barium content. (which leads me to
>believe it IS toxic.
>
>Thanks to everyone for your response!
>
>Diane
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
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