Snail Scott on sun 10 oct 10
As some of you know, I teach at an institution with
severely limited dry mixing facilities. Due to budget cuts,
I have sworn off buying any premade wet underglazes/
engobes, but want the students to have some experience
with their use.
I presently mix colored slips from a dry clay premix plus
oxides, and to produce an engobe for bisque application
I am combining two parts clay with three parts calcined
clay. This seems to give the optimum compromise between
shrinkage and brushability, but it's still not good. It tends
to flake off if even a little too thick owing to the raw clay
component, but using more calcined material gives poor
brushability. I am hoping to increase the calcined clay
component, and perhaps calcine some of it hotter than at
present (to reduce shrinkage), but improve the brushability
with additives.
Working from a normal recipe of materials is impossible, as
I am not permitted to have more than a few on premises.
So, I'd like to use just one additive, preferably not a dry one
(in order to minimize dust), but I won't be picky.
Before I go buying stuff to experiment with, I'd like to hear
some suggestions based on experience. Glycerine? Propylene
or ethylene glycol? CMC or other gum? Any other suggestions
for improving brushing properties, bearing in mind the need to
keep materials and dry mixing to a minimum?
Thanks,
-Snail
William & Susan Schran User on mon 11 oct 10
On 10/10/10 11:27 PM, "Snail Scott" wrote:
> Working from a normal recipe of materials is impossible, as
> I am not permitted to have more than a few on premises.
> So, I'd like to use just one additive, preferably not a dry one
> (in order to minimize dust), but I won't be picky.
>
> Before I go buying stuff to experiment with, I'd like to hear
> some suggestions based on experience. Glycerine? Propylene
> or ethylene glycol? CMC or other gum? Any other suggestions
> for improving brushing properties, bearing in mind the need to
> keep materials and dry mixing to a minimum?
Snail,
I mix all of my crystalline glazes with a solution of CMC, as these glazes
contain no clay and it is difficult to keep them from flaking off bisque as
they dry. I mix about 25 grams dry CMC with 1 quart of water. I usually jus=
t
add the CMC to water and let sit a couple days, then shake up to mix. I use
this solution instead of water. I brush on the glaze in several layers,
often up to 4 coats and never have it flake off. This might work for your
engobe application.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Jeanie Silver on tue 12 oct 10
Dear Snail
It seems like you are up against it...if you had even a rudimentary
inventory of ingredients I could send you the formula for slip that I have
used for 25 years in many different applications, temperatures and
atmospheres on 6 or 7 different clays. If you want it, I will send
it....but as to additives for greater handling qualities, my experience is,
the simpler, the better. The thing that I have found to be the best for
greater brushability is-soak your brushes in water for a few minutes before
you start, then squeeze water out and fully load your brush. Use the brus=
h
as much as possible at an angle approaching 90 degrees. Work decisively,
not tentatively, and use soft hake, calligraphy or soft watercolor brushes.
Bristle brushes are not good except for coarse hakeme type
applications...hope this helps
Jeanie in Pa.
Lis Allison on wed 13 oct 10
On October 12, 2010, you wrote:
> It seems like you are up against it...if you had even a rudimentary
> inventory of ingredients I could send you the formula for slip that I
> have used for 25 years in many different applications, temperatures
> and atmospheres on 6 or 7 different clays. If you want it, I will
> send it....
Ooooh, too tantalising! Any chance you would post your recipe to the list?
Lis
--
Elisabeth Allison
Pine Ridge Studio
website: www.pine-ridge.ca
Pottery blog: www.studio-on-the-ridge.blogspot.com
Garden blog: www.garden-on-the-ridge.blogspot.com
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