John Sankey on sun 15 apr 07
I want to build a semi-gloss food-safe true black for ^6, to
go on standard white stoneware. I'd prefer one that gives a
solid colour when thin, rather than thick.
The primary choices for black gloss additives seem to be:
red iron oxide (typically 10%)
manganese oxide (up to 4%)
cobalt oxide (1-2%)
chrome oxide (1% or less)
Some say that RIO is a frit at ^6, not a colorant.
I'm limited to the standard firings of my group kiln: bisque ^06
and glaze ^6 - no experiments possible with temperature.
Does anyone have any suggestions as to any of these?
Donna Kat on thu 19 apr 07
On Sun, 15 Apr 2007 07:50:04 -0400, John Sankey wrote:
>I want to build a semi-gloss food-safe true black for ^6, to
>go on standard white stoneware. I'd prefer one that gives a
>solid colour when thin, rather than thick.
>
>The primary choices for black gloss additives seem to be:
>
>red iron oxide (typically 10%)
>manganese oxide (up to 4%)
>cobalt oxide (1-2%)
>chrome oxide (1% or less)
>
>Some say that RIO is a frit at ^6, not a colorant.
>
>I'm limited to the standard firings of my group kiln: bisque ^06
>and glaze ^6 - no experiments possible with temperature.
>
>Does anyone have any suggestions as to any of these?
>
Our studio black glaze and many others use Red Iron Oxide (~7%) and Cobalt
(~1.5%) for the colorant. We also use RIO at 15% to make a Earth red
glaze (Toby's/Randy's Red). Again see frogpondpottery site for an
excellant black cone 6 glaze. These are for Oxidation firings. I avoid
Manganese and it isn't needed. Same for Chrome Oxide.
John Sankey on fri 20 apr 07
"So trial with Cobalt oxide and Red Iron oxide, giving blue and
orange, might be a good place to start... If Iron oxide gives a
greater red response with a selected base glaze add a small
proportion of Chrome oxide. If it tends towards yellow, Manganese
dioxide, which can give a purple response would be an appropriate
choice."
This is exactly the info I need! Do you know of a link to info on
the colours of the various common oxides in a glaze? Dare I
dream, spectral curves even?
My group's kilns are electric, so sort-of oxidizing.
John Sankey
Steve Slatin on fri 20 apr 07
The color effect of the different oxides differs depending
on the base glaze. To get a good idea of what the
different
color effects will be in different concentrations in
different
classes of base glaze, get yourself a copy of "Glazes Cone
6"
by Bailey.
It has wonderful pictures, and good sample glaze recipes.
Class-act ClayArter Alisa Clausen has some pages (check the
archive for details) with excellent samples. She does
great,
thorough, comprehensive testing.
Hope this helps.
-- Steve Slatin
Steve Slatin --
Well, he came home from the war
With a party in his head
And a modified Brougham DeVille
And a pair of legs that opened up
Like butterfly wings
And a mad dog that wouldn’t sit still
---------------------------------
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Ivor and Olive Lewis on sat 21 apr 07
Dear John Sankey,=20
There is information about adsorption spectra in W. Weyl, "Coloured =
Glass" This is now a very old book but he was the authority last =
century. Covers all the popular colourants.
Ivor
John Sankey on sun 22 apr 07
Ivor Lewis: "There is information about adsorption spectra in W.
Weyl, "Coloured Glass". This is now a very old book ..."
It's been reprinted twice, the latest in 1999. But, the lowest
price I can find is US$93 even for a used reprint copy :-(
Michael Bailey, "Glazes Cone 6" is a bit better at $30, but I'd
like to know how precisely it answers my colorants questions
before ordering it.
Seems a shame that, with all the pottery material available on
the web, no one has summarised basic oxide colours here. (At
least, I haven't been able to find it.)
Steve Slatin on sun 22 apr 07
John --
I understand your frustration expressed in the clip, below.
You haven't been able to find it because it isn't actually
possible to do it.
The colorant oxides aren't all that goes into glaze color.
The acidity of the glaze is significant. The opacity of
the glaze is significant. The interaction of one colorant
oxide with another is significant. The color responses of
the G I ions is significant (that is, two glazes
that are otherwise identical but one contains more sodium
and the second more potassium but have otherwise identical
constituents will be different). Likewise Group II
ions (calcium, strontium, etc.)
The mix of Group I to II ions is significant (say sodium
to calcium as the probably most common example).
Each of these things changes the color in a layer of glaze
with otherwise identical constituents.
The existence of a second layer (often found in boron-rich
glazes, where there's a visible separation between a
silica-rich layer and a boron-rich layer) is also significant.
That's why Bailey's book is useful. You may be able to
search a few pages on-line to get some idea of whether it'd
be useful to you. If you want to see, for example, the
effect of 1, 2, or 3% of an oxide on a calcium-rich or
potassium-richor sodium-rich base, Bailey's excellent.
To get a start, though, you can check June Perry's website
(Shambhala pottery) -- she has a summary of color and
mixing instructions for oxide washes that can be a good starting
point.
-- Steve Slatin
--- In clayart@yahoogroups.com, John Sankey
wrote:
>
>
> Seems a shame that, with all the pottery material
available on
> the web, no one has summarised basic oxide colours here.
(At
> least, I haven't been able to find it.)
>
>
Steve Slatin --
Took a hundred dollars off a slaughterhouse joe
Brought a brand new michigan twenty-gauge
Got all liquored up on that road house corn
Blew a hole in the hood of a yellow corvette
---------------------------------
Ahhh...imagining that irresistible "new car" smell?
Check outnew cars at Yahoo! Autos.
Kathy Stecker on sun 22 apr 07
This website below has quite a few color combinations under stains and
oxides I believe it's June Perry's? but can't find an actual name on the site.
Also look in the Mason stain charts in one of the ceramic catalogues ( I'm
looking at Axner's right now for example) or possibly on Axner's online? or
google Mason Stains? On the chart I'm looking at it shows the elements used to
produce their stains. It's at least interesting to see the 4 different
combinations for their blacks. Interesting that their colors all seem to have Chromium
for their greens-anyone know why they don't have copper greens and blues?
_http://www.angelfire.com/art2/shambhalapottery/_
(http://www.angelfire.com/art2/shambhalapottery/)
Kathy Stecker
Winter Springs, Florida
USA
************************************** See what's free at http://www.aol.com.
Ivor and Olive Lewis on mon 23 apr 07
Dear John Sankey,
My answer was given to satisfy a request for graphs of adsorption or =
transmission spectra of glaze colourant materials. Weyl addresses that =
issue. At $US 95 it would be good value but not necessarily for a =
potter.=20
If it is just a case of knowing which metallic oxides and carbonates =
then there are many textbooks that give such information, including the =
variations in hue and saturation due to the effects of various =
ingredients or absence thereof.=20
<to know how precisely it answers my colorants questions before ordering =
it.>> See if you library can get for you on interlibrary loan if they do =
not stock it.
<web, no one has summarised basic oxide colours here. (At least, I =
haven't been able to find it.)>>
On the Web, try Wikipedia. If it does not give the "griff" it may have =
the leads.
All the best,
Ivor
stephani stephenson on tue 24 apr 07
I use Mason stain 6600 'best black' for a rich, true, consistent black colorant in my glazes.
Stephani Stephenson
---------------------------------
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Ric Swenson on wed 25 apr 07
I agree....Mason Stain 6600 Black is the best.Ric
=20
=20
=20
> Date: Tue, 24 Apr 2007 19:34:35 -0700> From: revivalsteph@YAHOO.COM> Subj=
ect: Re: Black Colorants> To: CLAYART@LSV.CERAMICS.ORG> > I use Mason stain=
6600 'best black' for a rich, true, consistent black colorant in my glazes=
.> > Stephani Stephenson> > > ---------------------------------> Ahhh...ima=
gining that irresistible "new car" smell?> Check outnew cars at Yahoo! Auto=
s.> > _____________________________________________________________________=
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Ron Roy on thu 26 apr 07
Hi John,
One of the finest books for studio potters is The Potters Dictionary of
Materials and Techniques by Frank and Janet Hamer - a little pricy but
there are many references to how colouring oxides react with differ kinds
of glazes.
That book is the first on my recommended books for potters list - you will
never regret having it.
RR
>--- In clayart@yahoogroups.com, John Sankey
>wrote:
>>
>
>>
>> Seems a shame that, with all the pottery material
>available on
>> the web, no one has summarised basic oxide colours here.
>(At
>> least, I haven't been able to find it.)
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Alisa Clausen on thu 26 apr 07
On Thu, 26 Apr 2007 12:32:35 -0500, Ron Roy wrote:
>Hi John,
>
>One of the finest books for studio potters is The Potters Dictionary of
>Materials and Techniques by Frank and Janet Hamer - a little pricy but
>there are many references to how colouring oxides react with differ kinds
>of glazes.
>
>That book is the first on my recommended books for potters list - you will
>never regret having it.
>
>RR
My Hamer and Hamer never goes back on the bookshelf. It has a permanent,
pushed around but never removed, place on my desk. I use it all the time
and always read something either new and useful or an important reminder.
I also think it is my number one reference. I hardly ever remember that
it is alphabetic and find so much stuff along the way looking up what I
needed.
Best regards, Alisa in Denmark
Ron Roy on thu 26 apr 07
The oxides used for this stain are Chrome, iron, cobalt and nickel.
There is a chrome free - #6616 with cobalt, iron and manganese.
And # 6650 is cobalt free using chrome, iron and manganese.
RR
>I use Mason stain 6600 'best black' for a rich, true, consistent black
>colorant in my glazes.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on fri 4 may 07
Dear John,
Strange, I find that ice crystals gradually grown in one of our freezers =
rather than sublime away, but the other one is self cleaning, aided by a =
flow of warmer air every few hours.
Yes, I agree, there is always some pressure from the surface of any =
material, even from gold at room temperature, due to thermal agitation. =
So, as I hinted, many of the things we employ might be volatilising as =
temperature climbs.
But to get Green sesquioxide to change into some red compound must =
involve some form of chemistry, possibly the formation of some sort of =
metallic chromate. Chrome oxide CrO3, the stuff that is reputedly =
carcinogenic is a red crystalline solid with a melting point of about =
150 deg C which decomposes at about 250 deg C.
Was Gerstly Borate implicated in the spray of particles around kilns a =
long time ago?
Thanks for responding.
Best regards,
Ivor
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