Marni Turkel on mon 20 may 02
My black mat glaze uses a stain containing chrome and I want to
replace it with some combination of oxides that does not contain
chrome. I am firing c5 electric.
I can get a very good black in glossy glazes with iron and cobalt,
but all of my efforts so far on several different mat base glazes
yields varying shades of dark brown, nothing close enough to a black
to pass. 8% red iron oxide with 4% cobalt carbonate is the best so
far, but it is still a brown. I will try larger amounts of one and/or
both. Combinations of iron, cobalt and manganese have been less
successful than just iron and cobalt.
Before I knock myself out testing I thought I would ask if it seems
reasonable to expect a chrome-free BLACK in a mat base. This will be
used on vases and flower arranging containers so it needs to hold up
at least to mild acids--floral preservatives are acid and can affect
unstable glazes over time.
Any information to help me understand the issues or suggestions on
successful oxide combinations would be appreciated.
Marni
--
Marni Turkel
Stony Point Ceramic Design
2080 Llano Rd 1B
Santa Rosa, CA 95407
Phone: 707-579-5567
Fax: 707-579-1116
http://www.marniturkel.com
Paul Lewing on tue 21 may 02
on 5/20/02 6:25 PM, Marni Turkel at marni@MARNITURKEL.COM wrote:
> My black mat glaze uses a stain containing chrome and I want to
> replace it with some combination of oxides that does not contain
> chrome. I am firing c5 electric.
Marni, Mason also makes a chrome-free black stain (as well as a cobalt-free
black stain). Have you tried that. I use a lot of it to make a gray-blue
at a concentration of 6%. At higher concentrations, it tends to break up
into gray-blue with brown crystals, but it might make black inn another base
glaze.
And why don't you want chrome in your black glaze? Just curious.
Paul Lewing, Seattle
Marni Turkel on wed 22 may 02
Paul,
Thank you for the suggestion. I do use Mason's chrome-free black
stain in several glazes. It is usually interesting, but I've never
seen it produce a black.
I am working on changing my glaze palette. I have several glazes I
want to use that contain titanium and they are getting muddy or
"smokey" when there is chrome nearby in the firing, it doesn't even
have to be on the same shelf. I have been using a green glaze that
contains copper and I want to get rid of it because of leaching and
because it fumes an off-white glaze I sometimes use. This green glaze
is not affected by chrome and does not affect titanium-bearing
glazes. I am looking at a green from either chrome or a combination
of cobalt and titanium which would put it in a segregated category
and severely cut down my options for loading. It seemed that a
chrome-free black would make loading kilns much easier as it could go
in with either chrome or titanium and make it easier to fill a kiln.
I thought life would be easier if I could get more glazes that didn't
have to be segregated, but, of course, it is more complicated that I
expected.
Marni
--
Marni Turkel
Stony Point Ceramic Design
2080 Llano Rd 1B
Santa Rosa, CA 95407
Phone: 707-579-5567
Fax: 707-579-1116
http://www.marniturkel.com
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