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looking for cone 04 glaze with depth

updated sat 16 sep 06

 

Ryan Forrey on fri 15 sep 06


Hello,


I've been testing a few glazes recently to be applied on an earthenware
clay body. I'm starting with a basic clear and adding zircopax to
opacify, then adding oxides and stains. These glazes are intented to be
sprayed on, so most of the results so far have been very flat almost like
spray paint. I know it's hard to get the disired affect at such a low
temp. Can any one give me some advice or glaze recipes for some glazes
with some depth and crystal growth. I imagine rutile and TI would help.

Thanks,

Ryan Forrey
Greenfield Village Pottery

Laurence Lavagne on fri 15 sep 06


bonjour, I think also that it is very difficult to get any sort of life
out of low fire glazes. I make lines of dinnerware using 06 glazes, I use
either clear that I stain with Mason Stains or commercial color glazes
like the Duncan. What I do is that I apply on the green ware(dry) some
underglazes that I then carefully rub into the piece with a sponge or a
very fine steel wool to create a sort of uneven background then I bisque
at 04, then I brush my piece with different colored glazes(like a green
and a blue) making sure that I do not mix them too much to keep some
variations of colors. This technique is time consuming and add some
manipulation to the green ware but it is the only way I found up to now to
have something with some nice bright colors and a little depth. I am right
now trying to see if I can speed up the process in dipping my pieces and
keep an ok result...will see. hope this will help.
laurence

Stephani Stephenson on fri 15 sep 06


Ryan
it can be done at cone 04

at cone 04 you will be likely using powerful fluxes such as frits
some common ones are 3134, 3195,3269, 3124, also 3110, etc,etc,
other fluxes used at that temp have traditionally included Gerstley
borate, lithium, calcium ,sodium , magnesium as an auxilliary flux,
and other or boron fluxes.
(read material on safety issues and solubility issues, etc.)
a frit or combination of frits often makes up as much as 85% of a glaze
at that temp so

if I were starting from scratch I would first do button tests of all
of the different frits and major fluxes just to observe their fired
qualities
than I would do grid tests, something I myself don't do often enough
my own preference being Ian Currie's method
to see how silica and alumina affect the visual quality of the fired
glaze.
you may discover a good glaze by doing a grid test with the base
fluxes in your current glaze
one value of the grid method is it can boil down 100 hours of testing
into , say 20 hours of testing
with organized, understandable results.

as you do the' hands on' 'I can see it with my own eyes' approach ,also
look at the formula, to try to understand what you are seeing by
studying the glaze composition via glaze calculation.


slow down your cooling rate in the kiln, to allow for crystal
formation

clay body has an enormous effect on how the glaze behaves. how about
using slips under the base glaze?

try substituting the clay in your glaze. for example, instead of
Kaolin, try subbing a % ball clay or red clay or native clay

trace elements such as phosphorous, those other unidentifyable trace
elements in wood ash, gerstly borate,unrefined materials ....
the bane of chemists, they can add that visual "je ne sai pas quoi"?
(my french is rusty, help Eduoard !)


colorants and % of colorants also affect glaze quality.

materials that come to mind which play a role :

Titanium and Titanium bearing compounds.
small amounts of lithium, under 5%, if you choose. try to resist the
temptation to use too much lithium.I have to say this because it it can
be very active visually but leads to problems with glaze durability,
solubility, fit(shivering), and read health considerations.
zinc
calcium
boron compounds
coloring oxides




aside from this, and this is an issue which I do not feel I have I
have the all encompassing knowledge or vocabulary to speak with
authority on

there are so many complex interactions....and enough resources out
there to explain better than I , but I'll try to hash this out (good
practice) and welcome any advice on this myself....

the way I visualize it is : getting depth with a glaze seems to me to
involve not only chosen materials but percentages and ratios of those
materials
and that is where it gets complex.

for example, when you read up on mattes you read about silica mattes,
alumina mattes, magnesia mattes and calcia mattes... they all have
different qualities.
one way of putting it is you saturate or over saturate a solution
with an element, enough that it precipitates out upon cooling rather
than remaining bonded or in solution, or it forms crystalline
compounds and those precipitate out of solution on cooling. Those
undissolved or precipitated compounds are what visually affect
light transmition and reflection as you view the glaze . That is
what gives you a true matte (rather than underfiring), and what also
affects 'depth' or 'complexity' in a glaze.
the precipitated compounds can
also provide visual interest.
Also , the other thing about 'depth' I think has to do with how where
elements and compounds are deposited on the clay form and surface.
if the glaze 'breaks', for example, some compounds are carried away
into the low spots while the glaze is quite fluid, into the pools and
furrows of the surface, while other , materials in the clay or glaze
which are not dissolved and carried away are left on the high spots
...(perhaps due to their particle size and weight, perhaps they are
grainy or other materials in the clay body itself which interract
with the glaze and are then are exposed visually where the glaze is
thinner)
so there is a physical element , say a kinetic , as well as a chemical
element and a temperature element .
I cannot explain crystal formation or phase separation or any of that
technically, to any degree that resource materials in text and online
can, but

meterials melt not only at different temperatures but at different
times and t different rates .At different concentrations they form
different compounds and precipitate out of solution in different ways
,rates and temperatures.
(If that explanation isn;t as clear as a dry underfired matte I don't
know what is......)
so it , to me , is the material itself , a combination of the
materials, the %, the clay and the firing and cooling rate.

I have an aventurine glaze for example that is nothing but a very fluid
frit(low or no alumina), and something like 10% iron oxide. On slow
cooling ,this glaze gives me luscious metallic copper penny
flecks/crystal/sparkles, like one of those fleck saturated car paint
jobs, it's kind of maroon where thin, and not a particularly useful
glaze really but the sample is one you can pull out and drool over....
any way, my point is... you can get a million glazes using iron and
fluxes ...

I 'd love to take a full on year to study this
good luck in your venture







Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com

Edouard Bastarache Inc. on fri 15 sep 06


Hello,

some of my C/04 glazes on this blog :

http://04glazes.blogspot.com/


Later,



Edouard Bastarache
Le Franšais Volant
The Flying Frenchman

Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.pshcanada.com/Toxicology.htm
http://www.flickr.com/photos/30058682@N00/
http://thepottersshop.blogspot.com/

Bruce Girrell on fri 15 sep 06


Ryan Forrey wrote:

> I'm starting with a basic clear and adding zircopax to
> opacify, then adding oxides and stains.

Laurence Lavagne wrote:
> I use ... clear that I stain with Mason Stains

What's the common element here?

It is my experience that stains produce the most lifeless of colors. If you
want to color a clay body, they're fine, but for a glaze you get color but
no depth.

Stephani has already covered most of the bases. A Currie grid can be labor
intensive, but provides the opportunity to discover glazes that you would
have never thought of trying.

For colorants, copper can produce a complete rainbow of colors at ^04
depending on what you do with it. Cobalt, of course, will be blue no matter
what you do with it. Iron in oxidation will give you some nice reds and
browns. I'm not sure whether you will get much activity out of the rutile at
that temperature or not. It may depend on the fluxes.

All in all, try various oxides and forget the stains.

Bruce Girrell