Jim Tabor on fri 28 feb 03
Kurt Hord's post on spodumene substitute was wonderful for those without
glaze calculating software and comfort to those with it. Aside from
being math challenged, the calculation tedium is too much of a
distraction from other pressing priorities I have like making clay,
glazes, and firing kilns for 70 students a day. In my stacks of all the
notes and glaze books collected in 3 decades are pages of the process to
do what Kurt described in his post. I abandoned the practice in favor of
line and triaxel blends with way too many test tiles as I have just
realized the value of glaze calculating software. Although I bought
Hyperglaze early in it's release (early/mid '90's), I toyed with it and
didn't make the connection as needed. Richard Burkett has been great to
bring his program (HyperGlaze) and other support to the pottery
community and deserves to be a saint in the clay church. The
opportunity to explore the new GlazeMaster program by John Hasselberth
has me excited.
I got tests from the kiln today that were exactly what I was looking for
from the numbers. Using Hammer's alumni/silica ratio for the cone 1 temp
range, and expansion around 70, as established by other working glazes
on my claybody, the range from vitreous engobes to satin matts and egg
shell matts were perfect. I was impressed.
When I went to school to make the glazes, I discovered I was out of frit
3195 and had to go back to the computer to adjust for the target balance
of silica, alumina, and magnesium on the matts. Juggling the talc,
dolomite, frits 3124, 3134, and silica gave me the target numbers and
the mix worked great!! Previous testing methods with triaxel blends have
resulted in several more firings for the same results. My Ceramics II
students are working on their invented glazes and using Hamer's numbers
as a guide in the GlazeMaster program. I'll let you know how they do in
the next 2 weeks.
The GlazeMaster program was easy for me to figure out in the first beta
version without any documentation. I explored all the options within an
hour and was making new glazes. The material database was limited but
covered most things I have in stock. On the Main Menu options, I like
the one with the glaze and material listed because you can look at the
properties of a material next to the glaze for consideration as an
inclusion in the glaze and calculate the adjustment for the numbers
needed in the target. Adjust the amount or change materials and
recalculate until they meet your need. Types of fluxes that impact color
are a consideration but you need to also consider the alumina/silica
ratio for stability at the temperature you are firing. Consult Hammer.
His limits "should" be a part of glaze software but I haven't seen them
included as a reference.
Digatalfire.com has a great database and calculating programs to also
consider. There are others I have not looked at but as a tool for glaze
development, get a program!!
Jim Tabor
Carol Tripp on sat 1 mar 03
Hi Jim,
Twice you mention Hamer's limits but I can't seem to find them in my copy.
I am sure this is a case of missing the obvious but could you please give
the heading and location of the list? Thanks very much.
Best regards,
Carol
Dubai, UAE
Where I am off to explore the Dubai Art Centre glaze chemical store room to
see what's available.
Jim wrote, in part:
>Using Hammer's alumni/silica ratio for the cone 1 temp... Types of fluxes
>that impact color
>are a consideration but you need to also consider the alumina/silica
>ratio for stability at the temperature you are firing. Consult Hammer. >His
>limits "should" be a part of glaze software but I haven't seen >them
> >included as a reference.
>
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Jim Tabor on sat 1 mar 03
Hi Carol-
Hammer's book is at school and I will be there for a few hours this
afternoon. If you look near the back, with tables and references, you
will find it. I'll email you with the page# when I get back. Look on
John Hasselberth's site noted below for a wealth of info on the topic.
He covers the history of limits and includes limit tables.
http://www.frogpondpottery.com/glazestab.html
Off to test more glazes,
Jim Tabor
Carol Tripp wrote:
> Hi Jim,
> Twice you mention Hamer's limits but I can't seem to find them in my copy.
> I am sure this is a case of missing the obvious but could you please give
> the heading and location of the list? Thanks very much.
> Best regards,
> Carol
> Dubai, UAE
> Where I am off to explore the Dubai Art Centre glaze chemical store
> room to
> see what's available.
>
>
>
>
> Jim wrote, in part:
>
>> Using Hammer's alumni/silica ratio for the cone 1 temp... Types of fluxes
>> that impact color
>> are a consideration but you need to also consider the alumina/silica
>> ratio for stability at the temperature you are firing. Consult
>> Hammer. >His
>> limits "should" be a part of glaze software but I haven't seen >them
>> >included as a reference.
>>
>
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