Joyce Lee on tue 10 oct 00
I don't mean to insult all those of you who may know a great deal about
many glaze testing methods when I'm only familiar with a couple ....
but, just in case one that Robin Hopper delineates has escaped you, do
you ever use the (can't remember the method's name right now) one where
you use a base glaze and add colorants (oxides, carbonates or stains) in
escalating percentages to it? Like 2.5% 5%, 15%, 25%, etc.... except
with cobalt or copper reds where the percentages never run so high. One
base glaze plus additions of cobalt, chrome, rio, rutile etc could yield
easily 25 test tiles and more, especially if you then work with layering
or feathering the glazes together on additional tiles.
In his book, "The Ceramic Specturm" .... on page 135 Chapter 15 'Color
Testing, Mixing and Blending'... Robin demonstrates how to use 100 grams
of base glaze ... then form 10 grams of colorant into a small pile;
finally the pile of colorant is flattened into a rectangle with a
fettling knife (or other tool) and divided into sections, each section
representing a percentage, so that you don't have to weigh each of those
small amounts.... not a precise nor scientific method, but very workable
for those of us who are not gurus and never will be.
Hopper's descriptions of triaxial blendings and crossblendings is
simplified also, which allowed me to get over the fear of mixing
chemicals and understand some of what I'm doing.
Again, my intention is not to insult your intelligence nor experience,
but to offer information that helped ME to those of you who are inspired
by Alisa's great contributions to try some testing yourselves... but are
put off by the detailed and generous programs that are available. Some
gurus don't quite understand just how ignorant of process a few of us
are ...... namely, me. I recall clearly how confusing even this
simplistic approach seemed when I first tackled it ... if a glaze didn't
come in a Brown Bag, I wanted no part of it. Then I discovered
RECIPES... wow! just like cooking, a concept I understood .... find a
good, experienced cook and get their recipes .... then a clayarter
recommended Hopper's book..
Joyce
In the Mojave
Craig Martell on sat 14 oct 00
Joyce, in a very diplomatic fashion sez:
>I don't mean to insult all those of you who may know a great deal about
>many glaze testing methods when I'm only familiar with a couple ....
>but, just in case one that Robin Hopper delineates has escaped you, do
>you ever use the (can't remember the method's name right now) one where
>you use a base glaze and add colorants (oxides, carbonates or stains) in
>escalating percentages to it?
Hello Joyce:
I used to do the above before I became an afficianado of volumetric
blending. I was introduced to the volumetric method thru Ian Currie's
first book.
> In his book, "The Ceramic Specturm" .... on page 135 Chapter 15 'Color
>Testing, Mixing and Blending'... Robin demonstrates how to use 100 grams
>of base glaze ... then form 10 grams of colorant into a small pile;
>finally the pile of colorant is flattened into a rectangle with a
>fettling knife (or other tool) and divided into sections, each section
>representing a percentage, so that you don't have to weigh each of those
>small amounts.... not a precise nor scientific method, but very workable
>for those of us who are not gurus and never will be.
Get real Joyce, you don't have to be a "guru", whatever the hell that is,
to do all sorts of glaze tests and blends and do them well and
accurately. Anyway, I've used the above method long ago and it works OK
and will certainly give you a ballpark idea of color gradients and
saturation points. Now, getting back to my volumetric dissertation, I do
this with syringes. Mix two 100 gram batches of a glaze base. To one of
these, add 10% of a colorant and add nothing to the other one. Mix and
screen the two batches. Then, using a graduated cylinder that measures
liquid in millilitres, adjust both batches to the same volume. Then, using
a 10cc syringe you can do the blends. Place 11 small cups on your
immaculate work table. You already have the 10% test mixed. Next, place
9cc's of the 10% batch in a cup with 1cc of uncolored glaze. Now you have
a 9% colorant batch blended. Then you go to 8cc and 2cc and so on. You
can do as many colorants as you want, 2, 3, or 4. You can use line blends,
triaxials, and quads to blend colorants into glazes and slips for
testing. You get a lot of information with a small amount of weighing,
mixing, and sieving. This is a very accurate method.
I'll shut up now so you can get back to your testing.
later, Craig Martell in Oregon
Ron Roy on wed 18 oct 00
First I want to make it clear - There are real advantages to the imperical
method of mixing materials together - In fact I often give glaze revisions
in this way because it is a faster way of getting the answer.
It is also true that the oxide approach (calculating molecular formulas) is
no less valuable. In fact - for solving glaze problems and substituting
materials it is better and - you get valuable (essential is a better word
to me) information on fit and durability which does not come with any
mixing technique.
It is important to know your materials and what they contribute to the
final clay or glaze and the analysis of those materials is the way to
understanding.
Trying to get important information from just looking at a glaze is fast
becoming old fashioned.
RR
> but are
>put off by the detailed and generous programs that are available. Some
>gurus don't quite understand just how ignorant of process a few of us
>are ...... namely, me. I recall clearly how confusing even this
>simplistic approach seemed when I first tackled it ... if a glaze didn't
>come in a Brown Bag, I wanted no part of it. Then I discovered
>RECIPES... wow! just like cooking, a concept I understood .... find a
>good, experienced cook and get their recipes .... then a clayarter
>recommended Hopper's book..
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
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