Rosanne on mon 11 oct 04
Is nickel volatile and will it affect neighboring pieces in a kiln? I am
fairly new to crystalline and I've run across a question that I can't find
an answer for.
In the past I've had good success with Fa Shimbo's Vesuvius glaze. It is
usually a transparent ground with white crystals but in my last firing
every piece glazed with Vesuvius has blue speckles. I was testing a new
glaze that has nickel in it and I'm wondering if the spots are from the
nickel or if they came from contamination possibly from the sieve or
perhaps a brush that wasn't cleaned properly. The test plate with the
nickel was at the bottom of my kiln and I have an envirovent installed on
the kiln. One of the contaminated pieces was at the top of the kiln the
rest were in the middle. The crystals in my copper green glaze have a
violet =91hue=92 on the edges (very pretty but not what I was expecting)and =
I'm
wondering if that is from the nickel as well.
William Melstrom on mon 11 oct 04
Rosanne:
You might get better responses to your query by asking your question here:
http://crystalline-ceramics.info/bbs/index.cgi
From the info that you have supplied, it is hard to tell what is going on.
Are the speckles just stray colorant -- maybe cobalt? -- or are they
crystals? Not all crystals are well-shaped, they can often look like
"speckles."
Nickel can produce blue crystals. Nickel can modify other colorants. But,
in my experience, nickel is not particularly volatile, that is, it doesn't
"jump" to other pieces. See what others at the above forum think.
William Melstrom
www.handspiral.com
Is nickel volatile and will it affect neighboring pieces in a kiln? I am
fairly new to crystalline and I've run across a question that I can't find
an answer for.
In the past I've had good success with Fa Shimbo's Vesuvius glaze. It is
usually a transparent ground with white crystals but in my last firing
every piece glazed with Vesuvius has blue speckles. I was testing a new
glaze that has nickel in it and I'm wondering if the spots are from the
nickel or if they came from contamination possibly from the sieve or
perhaps a brush that wasn't cleaned properly. The test plate with the
nickel was at the bottom of my kiln and I have an envirovent installed on
the kiln. One of the contaminated pieces was at the top of the kiln the
rest were in the middle. The crystals in my copper green glaze have a
violet 'hue' on the edges (very pretty but not what I was expecting)and I'm
wondering if that is from the nickel as well.
Ivor and Olive Lewis on tue 12 oct 04
Dear Rosanne,
I take it we would be correct in making the assumption that your are
talking about Nickel Carbonate or Nickel Oxide?
Specks of colour seem to indicate contamination via your sieve.
Contamination due to volatilisation would give a general blush of hue
over a surface. It is doubtful that diffusion would cause sufficient
segregation to make a deposited vapour migrate to the crystal
boundaries.
Having a flow of air through your kiln would tend to mitigate the
effects of volatile compounds on the remainder of the load, though the
draft might not be strong enough to keep particulate matter in
suspension.
Nickel Oxide is highly refractory and I have seen it cause matting and
opacity when added, in excess, to an otherwise bright transparent
glaze. This seems to indicate that it has a limited solubility in a
silicate melt.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
william schran on tue 12 oct 04
Rosanne wrote:>usually a transparent ground with white crystals but
in my last firing
every piece glazed with Vesuvius has blue speckles. I was testing a new
glaze that has nickel in it and I'm wondering if the spots are from the
nickel or if they came from contamination possibly from the sieve or
perhaps a brush that wasn't cleaned properly.<
Sounds like contamination is the problem.
I also work with crystalline glazes, mixing small (100-200 grams)
batches at a time. I usually mix a larger amount of the base glaze,
sieve dry, then divide into the smaller amounts and add the colorants
to the smaller batches, add my gum solution and sieve again. After
sieving with colorant & liquid, I wash sieve & brush with soap &
water between batches.
But I think I'm going to change to using an old blender to mix the
small base/colorant/liquid batches. I think it will be easier to
clean up between batches. Need to be sure and get a blender with
glass top.
Bill
John Rodgers on tue 12 oct 04
william schran wrote:
>
> But I think I'm going to change to using an old blender to mix the
> small base/colorant/liquid batches. I think it will be easier to
> clean up between batches. Need to be sure and get a blender with
> glass top.
You might consider working wtih one of those hand held electric mixers -
the types with the single small blade. The can be purchased for $10-12
in many places, or maybe even cheaper if acquired at a thrift store or
the like.
I have a couple that I used for small batches of glaze. I also use them
to make small quantities of soap too.
I got the tip on using these from Lisa Skeen a few years ago.
Regards,
John Rodgers
william schran on thu 14 oct 04
John wrote:>You might consider working with one of those hand held
electric mixers -
the types with the single small blade. <
Hmmmm... we have one of them in the studio at school, I'll give it a
try with this hand mixer and with the blender - see which might work
better. I would imagine with a small quantity I'll need to find a
mixing container with a flat bottom - perhaps a pyrex measuring 3 cup
container.
Bill
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