George Koller on mon 29 sep 03
Hi Again Gang,=20
Thank you Ivor, and thank you Tom Buck for info/advice.
When we dispense "higher" concentrations of Iron to our Cone 04=20
zinc oxide opacified base white glaze we start to see what I now
think is "micro-crystalline" growth. (One day we had never seen
this before, the next day we "need it". We are hooked, whatever
this is we are seeing.)
...What we see is a "maze" of light green "lines" usually about
1/4" long and often at right angles to each other. White gaps b
etween. Rather subtle - not big radiating "classical" crystals at=20
all. And this is what we want.
What I'd like to do is compile a list of things we can do without
starting a major research project to encourage this to happen. =20
Here is what I have picked up so far:
1. Zinc oxide is a good media
2. Higher concentrations of metal colorants (Iron, Copper, =
Cobolt...) may help
3. Cooling cycle is most critical.... lots of advice.... but look =
to slow down
cooling starting at something like 100d F below melting point.
4. Thicker glaze coating is better. (from FA's site)
5. Titanium dioxide might encourage crystal growth (not sure at =
about at cone 04)
=20
6. Not sure yet but Laguna and BigCeramicStore seem to have =
standard glaze bases
that are designed to support crystal growth - maybe Macro and =
Micro?
7. I added some Pottasium DiChromate to several test tiles and this =
changed the
crystal shape as well as changed the color to a darker green. =
I am encouraged to=20
experiment with just a percent or two of Copper also to our Fe =
(which is now=20
being dispensed as a Ferric Ammonium Citrate solution at 45g / =
100CC).
8. What we are seeing may be called Aventurines. See =
Parmalee/Harman for more
information / review.
9. (Boosting the red iron oxide content of a reliable Tenmoku style =
recipe=20
up to 15 % or more can get you some very nice Blue Haematite =
crystals.
.....gk note: probably na to low temp?)
10. Tony Hanson's site has an eBook version of the book: "Crystal =
Glazes: Understanding the process
and materials" by Fara Shimbo. However, when I down loaded =
it (?) it was only 10 pages - mostly
an intro and the index. Not sure what happened but eBook =
concept strikes me as a really good one -=20
you are getting a "subscription" to future updates - not just =
a static book. (Ahhh those cutting=20
edge Canadians.)
=20
This is where I am right now except for some additional too vaque for me =
to put into words info from
the archives ie maybe 4 years ago a good clayart thread on this with a =
Ron Roy response or two) =20
Will appreciate additional advise.
Note: We are looking to keep this all at cone 04 for now. We are =
looking to do this on
a regular and predictable basis.
Many thanks for assistance,
george koller
sturgeon bay, wi - door county
northport, mi - leelanau county
two great places separated by 100 miles of great lake.
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