k.m.whipple@ATT.NET on mon 2 sep 02
I'm hoping someone can walk me thru the steps of trying
to salvage a bucket of glaze--at this stage in my clay
life, i can't afford to ditch such a quantity of
materials.
The glaze is Ron and John's Bright Sky Blue, and for
clarity, here is the recipe:
G-200 Feldspar 20 (i subbed custer)
Frit 3134 20
Wollastonite 10
EPK 20
talc 11.5
Silica 18.5
Cobalt carb 1%
Rutile 6%
RIO .5%
My notes from the mixing are no help, i crossed my I's
and dotted my t's meticulously. The first batch came
out fully melted, but not the right color--more
greygreen than blue, tho it did go smoky/baby blue
where overlapped with white. I found some discussion on
R & J's site that suggested this might have happened
because i cooled the kiln too slowly for that glaze, so
on the second go round, i didn't fire down, just let
the sitter turn the kiln off. This second round is
probably the ugliest thing i've ever seen: incredible
crawling and a truly yucky, pasty olive patched with
splotches of insipid powder blue where it was thicker--
which is where it crawled worst, of course---ick.
So:
*is custer so different that G-200? my notes/research
say they are both potassium spars and can be
substituted.
*i diagnose that i must have left out some flux
(that crawly underfired look...); does that sound right?
*but might my rutile also be at fault for the color
problems? (my tests for Spearmint glaze also turned out
goose-poop ugly)
I have nearly all of a 5000 gm batch of this glaze left.
How does one begin trying to fix such a thing: i am
thinking i will have to measure out the liquid volume,
break it down into something i can work with, like cups
and quarts, and make some tests, a teaspoon more of
silica or spar or frit per 1/2 cup...if i get some
tiles that look good, extrapolate the quantities back
into the bucketful.
Any and all help will be greatly appreciated--
Kathy
Brooker, Fl
Lily Krakowski on mon 2 sep 02
WHAT YOU NEED FIRST is some strong coffee or some strong ice tea.
Then, as my mother would have suggested, wash your face with a nice cold
washcloth. And take it from there.
When you say first batch and second batch that suggests a MIXING error.
Sounds like you put in a lot more of something--maybe rutile --than you
should have. Or left something out entirely.
ALSO POSSIBLE that you did not sieve the whole 5000 gram batch--I find
stirring has limited success and always sieve--(see below) and something
vital stayed at the bottom.
Sieve the entire batch. Sieve it twice if you have any doubts.
Remove a quart or so, and DRY IT THOROUGHLY. An old roasting pan from the
thrift shop, lined with a piece of sort cloth (elderly roasting tins often
have rust spots--is a good wide surface for drying. Or you can use large pan
sugggested below.
Now weigh out small amounts of the dry stuff. Mix one up plain with water
and see if that does it--i.e., you did not mix well.
If you want wait till you have tested that test tile, before you "do"the
others.
Now--this is the more annoying part. You have six basic ingredients. Weigh
out NEW glaze OMITTING ONE INGREDIENT ENTIRELY. Your first batch would omit
the feldspar, the second batch omit the frit etc. You then mix the new
batches with what you have weighed out of the old. Each of these mixes
would have 1/2 of one original ingredient. Where you left out the feldspar
you would have 1/2 the feldspar and so on. Testing these will give you a
clue as to what you left out, or put too much of in.
since these tests will not have colorant added you also will learn whether
you overdid colorant.
Truth to tell this is a bit boring, although I have had to do it many times.
However. Next time you commit yourself to 5 K of any glaze be a dear and
weigh out each ingredient, put it in a plastic bag (1 gallon food storage
ones) and reweigh before dumping in bucket of water. As I need to weigh out
big quantities in batches, I use smaller bags--actually saved vegetable bags
from the supermarket--and then reweigh each. I.E. I will weigh out 3 five
hundred gram bags and one 350 gram bag of Whatever and reweigh before I
combine.
Let us know....
BELOW; for this kind of screening, make yourself a big sieve. Build a box
like frame out of 3x1 board, cover the bottom with silkscree fabric--I use
the kind they sell for glitter. Stretch the fabric tightly epoxy it on.
For a big box put a thin crosspiece of lath across the middle. I suggest
you shellac or polyurethane the wood beforfe adding the screen. Use such a
screen over a kitty litter pan--a new one, or Kitty will get mad--or a
plastic baby bath--something with a bigger opening than a dishpan or a 5
gallon pail
k.m.whipple@ATT.NET writes:
> I'm hoping someone can walk me thru the steps of trying
> to salvage a bucket of glaze--at this stage in my clay
> life, i can't afford to ditch such a quant00ity of
> materials.
> The glaze is Ron and John's Bright Sky Blue, and for
> clarity, here is the recipe:
>
> G-200 Feldspar 20 (i subbed custer)
> Frit 3134 20
> Wollastonite 10
> EPK 20
> talc 11.5
> Silica 18.5
> Cobalt carb 1%
> Rutile 6%
> RIO .5%
>
> My notes from the mixing are no help, i crossed my I's
> and dotted my t's meticulously. The first batch came
> out fully melted, but not the right color--more
> greygreen than blue, tho it did go smoky/baby blue
> where overlapped with white. I found some discussion on
> R & J's site that suggested this might have happened
> because i cooled the kiln too slowly for that glaze, so
> on the second go round, i didn't fire down, just let
> the sitter turn the kiln off. This second round is
> probably the ugliest thing i've ever seen: incredible
> crawling and a truly yucky, pasty olive patched with
> splotches of insipid powder blue where it was thicker--
> which is where it crawled worst, of course---ick.
> So:
> *is custer so different that G-200? my notes/research
> say they are both potassium spars and can be
> substituted.
> *i diagnose that i must have left out some flux
> (that crawly underfired look...); does that sound right?
> *but might my rutile also be at fault for the color
> problems? (my tests for Spearmint glaze also turned out
> goose-poop ugly)
>
> I have nearly all of a 5000 gm batch of this glaze left.
> How does one begin trying to fix such a thing: i am
> thinking i will have to measure out the liquid volume,
> break it down into something i can work with, like cups
> and quarts, and make some tests, a teaspoon more of
> silica or spar or frit per 1/2 cup...if i get some
> tiles that look good, extrapolate the quantities back
> into the bucketful.
>
> Any and all help will be greatly appreciated--
>
> Kathy
> Brooker, Fl
>
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Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
Marianne Lombardo on mon 2 sep 02
Not that this will help rescue anything, but I think I vaguely remember
either Ron or John saying something about this recently. Something about
some bad rutile going around.
Marianne Lombardo
Omemee, Ontario, Canada
> *but might my rutile also be at fault for the color
> problems? (my tests for Spearmint glaze also turned out
> goose-poop ugly)
Ron Collins on mon 2 sep 02
Hi Kathy...I know how frustrating to have a 5000g. bucket, but although I'm
no expert on much....I think that your adjectives referring to the Mastering
Cone 6 Glazes are a little harsh. People do small test batches, and while
they may not come out exactly like the full bucket, they let you know if you
are on the right trail. Many variables, such as your type of clay, how
clean was your bisque, was the glaze dried a day or two before firing, there
are many other things to work out before you get your groove going. I like
my Waterfall Brown even better than the photo of theirs, but I've been
playing with it a lot....but at first, just small batches. These glazes are
starting points, not all work for all situations, and many variables come
into play when trying for dependable, consistent looks. Glazing is so
frustrating, and personally, I hate the whole process of it, but testing,
it's necessary if you want to be success..,,,,there is a lot to understand
in their book, but certainly a great deal of information is there, but you
have to get out of chapter six for a while. Good luck to you......and by
the way....keep a bucket of mystery glaze to dump all your tests, both good
and bad....there was a well known potter a few months ago with an article
and a beautiful photo of her casserole glazed with her mystery glaze....so
there's hope for that bucket......Melinda
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