TONICLAYS@AOL.COM on wed 3 apr 02
My friend Todd has a question for the reduction/copper red experts. "If you
are firing in a reduction kiln with a lot of copper reds would you ever see a
lot of greenish flame...does the presence of copper ever affect the color of
the flame or is the atmosphere just not in a true reduction?" If you can help
him, I will forward the answers. Thank you, Toni Smith in Ohio
Craig Martell on wed 3 apr 02
Toni wanted to know if:
>does the presence of copper ever affect the color of
>the flame or is the atmosphere just not in a true reduction?"
Hi:
Absolutely! Copper will produce a green flame at the spyholes.
later, Craig Martell in Oregon
iandol on thu 4 apr 02
Dear Toni,
Many compounds are to some degree volatile at top firing temperatures. =
If the vapour is entrained in the flue effluent and that contains carbon =
monoxide, there is a probability that a green colour would be visible in =
the burning envelope of the flame which issues from the stack.
My younger grandson is fascinated by this phenomena when we are firing =
one of my kilns. I thought it was due to copper but I do not always have =
copper bearing glazes in the kiln. Checked with the spectroscope and =
could not see the spectral lines for copper. So it could be Boron.
Hope that helps.
Regards,
Ivor.
Jocelyn McAuley on thu 4 apr 02
> At 07:57 PM 4/3/02 EST, you wrote:
> >My friend Todd has a question for the reduction/copper red experts. "If you
> >are firing in a reduction kiln with a lot of copper reds would you ever see a
> >lot of greenish flame...
>
> Yep, lots of green flame, whether you're reducing or not.
With all due respect to those who've answered this thread, I can't help
but wonder if we're just following "pottery folklore" in regards to the
copper-green flame phenom.
I too have been taught that the green flame upon reducing copper-reds is a
sign of copper exiting the kiln (a bad sign if you want reds). However,
I've found the green flame to be more of an occurance with non-copper
glazes (for example I had an Olsen full of a manganese gold and a
barium glaze most recently that was a spectacular green). I've been
reading a book recommended by Fa Shimbo called "the Physics and Chemistry
of Color, (by Kurt Nassau) that elaborates on flame colors given off by
certain minerals. Its a simple procedure to help elucidate the identity
of an unknown mineral is to heat it in a gas flame. This technique was
pioneered by Bunsen, and a chart of flame colors is included in the book
(this also explains the varying colors of firework displays). It's
reported that:
lithium gives off deep red
sodium ............yellow
potassium..........violet
calcium............orange red
strontium..........crimson red
barium.............yellow-green
thallium...........green
borates............green
arsenic, antimony,
bismuth, copper
and lead...........blue
I've never fired a load that was exclusively copper reds, unlike many on
this list...
Has any one experienced the green flame with a load of copper red glazes
only... with the results of red glazes resulting from that fire?
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Eugene, Oregon http://www.ceramicism.com
Snail Scott on thu 4 apr 02
At 07:57 PM 4/3/02 EST, you wrote:
>My friend Todd has a question for the reduction/copper red experts. "If you
>are firing in a reduction kiln with a lot of copper reds would you ever see a
>lot of greenish flame...
Yep, lots of green flame, whether you're reducing or not.
-Snail
Snail Scott on fri 5 apr 02
At 10:30 PM 4/4/02 -0800, you wrote:
>I've found the green flame to be more of an occurance with non-copper
>glazes
> Has any one experienced the green flame with a load of copper red glazes
>only... with the results of red glazes resulting from that fire?
I've never fired much copper red. I have noticed that I
got greener flames if there was more copper in the kiln
load, though. In raku firing, also, the greenest flames
come from loads which include copper-bearing glazes. It
may not be the only cause of green flames, but it
certainly is one.
One thing I do a lot of is bronze casting. Nothing in
the furnace but Everdur bronze (95% copper, 4% silica,
1% manganese) and the silicon carbide crucible, and the
flames are fabulously, intensely green.
-Snail
Jim Mason on fri 5 apr 02
Jocelyn,
I use a fair amount of copper red glaze in the cone 10 reduction firings at
the CC where I take classes, but of course there are many other glazes in the
same kiln. In fact, it would seem very unlikely to me that one would ever be
able to have a firing that excluded everything except copper. I frequently
see a rather intense green emission from the stack after the initial
reduction, when we attempt to adjust the atmosphere to essentially neutral --
neither oxidizing nor reducing. (I can send a photo of this to someone who
might want to post it on a web site.) I think that the best explanation of
this is Ivor's who saw no copper spectral lines in the flame, but may have
identified boron as the source of the color. Anyway, my copper glazed pots
fired this way have typically had a very nice deep red appearance.
Best regards,
Jim Mason
Gibsonville, NC - on another beautiful day!
In a message dated 4/5/02 9:28:33 AM Eastern Standard Time,
jocie@WORLDDOMINATION.NET writes:
<< I've never fired a load that was exclusively copper reds, unlike many on
this list...
Has any one experienced the green flame with a load of copper red glazes
only... with the results of red glazes resulting from that fire? >>
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