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JUST RAKU
The Newsletter for Raku Artists and Raku Art Lovers
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May 2005
Issue #31
Published by
Gary R. Ferguson – Raku Artist
http://www.garyrferguson.com
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In This Issue
* While the Smoke Clears
* Fading Glazes Feedback
* Getting "that" Copper Matte Color
* Paragon Kiln FAQ Document
* Naked Raku Pictures
* Vanadium Stain vs. Vanadium Pentoxide
* Lasting Kiln Shelves
* Raku Web Links
* Workshops, etc.

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* While the Smoke Clears *

Yeah, I know. It's not May any more. Yes, this newsletter
is WAY late, but I figure better late than never, right?

I've changed the format of the newsletter a little bit,
which I think will help me get the issues out a little
easier and faster. Plus you should be able to tell what's
in each issue a little easier as well. Let me know what you
think.

One thing I wanted to make sure and tell you is CafePress
is having a sale. You get $10 off any order of $30 or more
until Jun 14, 2005. So hurry! Just use coupon code GRDAD05
(that is a zero-five) during checkout at any of my stores:

Just Raku Logowear http://www.cafepress.com/justraku
Got Raku http://www.cafepress.com/gotraku
Raku Secrets http://www.cafepress.com/rakusecrets

I appreciate your support – plus you get to save some coin.

As always, I look forward to your feedback, suggestions,
questions, and article ideas at:
editor@garyrferguson.com

Gary R. Ferguson
- Raku Artist –
pottery@garyrferguson.com

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Here is an easy (and free) way to support this newsletter.
Open a new eBay account by clicking on the link below and
select "register" at the top of the screen. Then look for a
deal and bid. Your support is greatly appreciated!
http://www.qksrv.net/click-411938-2202639
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* Fading Glazes Feedback *

Chris R. had the following feedback on the issue of fading
colors of some Raku Glazes.
---
Tom Buck in Ceramic Review Issue #159, May/June 1996, on
which the following is based, discussed the question of
"fading" glazes in an article.

The rainbow colors on a copper-matt pot are caused by
firstly reducing the metal oxides in the glaze back to
metal and, secondly, allowing that shiny metal surface to
oxidize slightly, which produces the light interference
that gives us the color effect we seek.

If the exposed metal surface is not protected, then it will
be subject to further oxidation - in the case of copper, it
may even oxidize all the way back to black copper oxide, as
your contributor has seen.

In other Raku glazes, the overall result is a porous ultra-
thin layer of colored glass on or near the glaze surface
whose complexes are open to attack by airborne oxygen,
moisture, and sulfur compounds. Put simply, the reduced
glaze is too porous and/or too easily affected by the
environment.

The original Raku glaze cut-and-try approach led to this
problem, since good glass does not come from impure calcium
borate (Colemanite/ Gerstley borate) and/or hydrated sodium
borate (borax). Neither one of these borate materials by
itself, nor any combination of the two together, will form
a long-lasting surface. Also, it takes more than 20%
Nepheline Syenite to provide enough silica and Alumina to
make the glaze durable.

A look at the Seger formulas for most Raku glazes shows why
they may change. They often lack sufficient silica (quartz,
flint or, chemically, silicon oxide, SiO2) to form a
durable glass. Many are also deficient in alumina (aluminum
oxide, Al2O3), which toughens glass and helps to seal the
glass surface.

Even Branfman's book http://www.garyrferguson.com/branfman
gives the same "80/20" borate glaze recipes of the 1960s
(with minor changes) although, to his credit, he also lists
newer balanced glazes that use frits in their mix (both
borate and alkaline frits).

So what is the answer to the fading problem? Seal the
glaze, either by using a varnish of some sort (but keep it
out of sunlight) or by making the glaze a viable glass by a
combination of intelligent alteration of the glaze
chemistry and LOTS of testing. Glaze chemistry is
fascinating and, once the initial concepts are grasped, not
too difficult to understand. Learn about it now. You'll
have to when the Gerstley Borate runs out anyway!
---
So it really boils down to the fact a copper matte glaze is
not "glass" enough to maintain the colors for extended
periods of time.

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If you are interested in making a little extra money for
taking on-line surveys, click on the link below. Go to
http://www.surveysavvy.com/?id=1424287 and click on 'Join'.
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* Getting That Copper Matte Color *

How do I get "that" copper matte color! I get this
question all the time, like the following:
---
I live in Portland and went to the big Ceramic show last
weekend at the Expo Center. I was checking out this Raku
booth and I really liked the glaze they used. I asked them
what is was, and he said it was copper sand with some or
all of the cobalt taken out and more copper added. I'd
love to get that recipe. I'm sending you a few pics of
another local artist who does the exact same glaze. It has
lots of magentas and purples and blues, and isn't glossy -
more like satin. Maybe you can tell me what it is if you
recognize it. I know they reduce in pine needles, which I
can't find any right now. Hope you can help me. Thanks in
advance!
---
Unfortunately, I'm never much help in these cases because
one thing I have learned about Copper Matte glazes, is it
is not so much the glaze formula as it is the application,
the firing process, and/or the reduction technique. The
exact same glaze can look wildly different depending on the
thickness of the glaze application, how it is fired, and
how it is reduced. Even if you knew all these, you will
likely still not get the same result every time. No potter
ever does.

So my recommendation is to try a couple of glazes either
from my website (http://www.garyrferguson.com/rakuglaz.htm)
or my ebook (http://www.rakuglazes.com) with various
techniques and see what you get and take good notes as to
what you do which may help you with future firings.

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Raku: A Practical Approach by Steven Branfman
The "nuts and bolts" how-to book of Raku
Order 30% off at: http://www.garyrferguson.com/branfman
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* Paragon FAQ Document *

Paragon has a 71-page Microsoft Word document of frequently
asked questions (FAQ) on electric kilns. There appears to
be many other useful documents on this site as well.
http://www.paragonweb.com/catalog.cfm?type=manuals

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Amazon sells more than books! Help support this newsletter
by using the following link:
http://www.garyrferguson.com/amazon
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* Naked Raku Pictures *

Here are some wonderful pictures of Naked Raku, both the
process and the finished product.
http://www.fromthepines.net/wally/

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"It's all your fault.......I was up all night reading "Raku
Secrets". I have been Rakuing for about ten years, and
still so much to learn. Your Raku Secrets gave me a lot of
new insight. Thanks so much". - Elaine S.
http://www.rakusecrets.com
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* Vanadium Stain vs. Vanadium Pentoxide *

I've had some question to the reference to Vanadium Stain
for the Yellow Crackle on my website and whether this is
the same as Vanadium Pentoxide.

The recipe is as follows:

Yellow crackle

Gerstley Borate 80
Cornwall stone 20
Vanadium stain 3-6

I do believe Vanadium Stain is different that Vanadium
Pentoxide. They are listed as different chemicals for
example on the following pottery supply website:
http://www.milehiceramics.com/glaze_chemical_prices.htm

The formula for Vanadium Pentoxide is V2O5 and the Vanadium
Stain is a Mason stain that is a combination of Vanadium
Pentoxide and Tin. So I would assume you could use
Vanadium Pentoxide and some Tin Oxide in place of Vanadium
Stain.

Heck, it is Raku – give it a shot!

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Raku Pottery by Robert Piepenburg
The must have "Bible" of Raku
Order at: http://www.garyrferguson.com/piepenburg
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* Lasting Kiln Shelves *

One reader wrote: How long do your kiln shelves last? I'm
finding they crack after about 10 firings. I've tried both
full and half shelves, same problem. Do you bisque fire
them in an electric kiln before using them in the Raku
kiln? How far up from the floor are they set? My torch
enters from the side (not bottom) and I'm using four 6"
posts. Do you use soft brick as shelf support? Any advice
to cut down on breakage would be most appreciated.
---
Well, I've been using the same kiln shelf for 3 or 4 years
now. It's not real big, about 12 inches across and I set
it on 3 pieces of soft brick. My burner comes in the side
below this shelf. The soft bricks have broken and crumbled
over time and have been replaced, but I never had a problem
with the shelf.

I do set all my pieces on stilts and not directly on the
shelf, which is probably a benefit.

I also take about one hour to fire to temperature. If you
fire extremely fast I could see this as a potential problem
as well.

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Alternative Kilns & Firing Techniques – James C. Watkins,
Paul Wandless http://tinyurl.com/72aaf
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* Click Away *

My eBay Listings http://tinyurl.com/tn08
Just Raku Blog http://justraku.blogspot.com
Just Raku Logowear http://www.cafepress.com/justraku
Got Raku? http://www.cafepress.com/gotraku
Just Raku Archive http://www.JustRaku.com
Fact Hive http://www.facthive.com

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Raku – John Mathieson http://tinyurl.com/3f5yh~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

* Workshops, etc. *

None Currently

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Raku: Investigations Into Fire by David Jones
Order 30% off at: http://tinyurl.com/8m5x
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JUST RAKU (C) Copyright 2002-2005 Gary R. Ferguson

P.S.