Cat Yassin on mon 28 oct 02
I've read most of the discussions on Manganese and my head is spinning! I
have a C. 6 Metallic Black glaze by Mary Berringer from CM April 2001 and I
really like it. It has a nice coverage and is consistent and I like the
effects I get when used under other glazes. I would like to use it on bowls
and mugs sparingly but I'm concerned about the Manganese. Here is the recipe:
Gerstley Borate 10.75
Whiting 5.48
Feldspar 78.86
Kaolin 4.91
Add: Cobalt Ox. 2.07
Copper Carb. 4.14
Manganese Diox. 4.14
Thanks for any input! If this isn't recommended for functional ware, does
anyone have a C. 6 Metallic Black that is comparable to this one?
-Cat
San Antonio, Texas
John Hesselberth on mon 28 oct 02
Hi Cat,
Sorry to rain on your parade, but this is not a good functional glaze.
It's not that it is so dangerous to the consumer--ingesting manganese is
not a big problem--you will find it in every multivitamin tablet. The
safety problem with manganese is with fumes or dust and that only
affects the potter.
The problem with this glaze is that it is not durable in use. After
going through the dishwasher for a year or so it will have lost its
sheen and maybe some of its color. It is just not a good functional
glaze. For that matter any time you see the word "metallic" in a glaze
name it is probably not suitable for functional work. That effect is
achieved by overloading the glaze with colorants of one kind or another.
And any time you do that you are making an unstable glaze that will
leach all kinds of stuff and not hold up in use.
Regards,
John
On Monday, October 28, 2002, at 10:02 AM, Cat Yassin wrote:
> I've read most of the discussions on Manganese and my head is
> spinning! I
> have a C. 6 Metallic Black glaze by Mary Berringer from CM April 2001
> and I
> really like it. It has a nice coverage and is consistent and I like the
> effects I get when used under other glazes. I would like to use it on
> bowls
> and mugs sparingly but I'm concerned about the Manganese. Here is the
> recipe:
>
> Gerstley Borate 10.75
> Whiting 5.48
> Feldspar 78.86
> Kaolin 4.91
>
> Add: Cobalt Ox. 2.07
> Copper Carb. 4.14
> Manganese Diox. 4.14
>
> Thanks for any input! If this isn't recommended for functional ware,
> does
> anyone have a C. 6 Metallic Black that is comparable to this one?
http://www.frogpondpottery.com
http://www.masteringglazes.com
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