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glaze and clay expansion

updated sat 10 sep 05


bill edwards on fri 9 sep 05

I have a minute before I leave for the shelter. Today
will be of shorter duration because I have to make
some pots or not pay my bills.

Most any glaze can be re-formulated for expansion
issues, it doesn't mean you are going to get exactly
what you got from the aesthetics of the glaze that may
have crazed in the past or it's very possible you get
that and more in some cases. Just keep that in mind!
The ideal is to get as close as possible and while I
or anyone else that does lots of calculating can
chemically stir you in the right direction, you must
test the changes and not take chances with large
batches regardless of who you believe to be the best
person for the job. It just doesn't work that way.

I have one clay I use a much higher expansion glaze
over than most. I use one other that has to have a
good deal less expansion but I know which glazes can
interact with one another to produce various results.
Keeping in mind if I am doing foodwares where I put
what and how its applied to reduce problems. Found
through experience and time and adjustments over

Clays sometimes change in consistency. How do we know
when? We have to ask. Glaze you make yourself can
change. How do we know when? You have to ask for new
analysis and if you do calculations, you imput the
newer analysis in your data banks and it changes the
composition through mathmatical means and spits out
the results that only you may understand if it's a
glaze you are used to working with on a particular
clay. There's no magic bullet but the science has
gotten much better and with people out there who work
at this hard, it gets better every day. Ron was right,
knowing the clay is a good start. Maybe we need to add
a clay analysis system into our methods but we can
complicate ourselves heavily trying to be
chemists/guru's/claybies instead of artists at times.
I do have the analysis for the clays I use but its a
full time job just keeping track of everything and
doing the house-hold chores and record keeping.
Sometimes we just have to believe that our suppliers
are doing the right thing and sometimes you can bet we
are not wrong. What worked for you last year may have
been the very 'KEY' you needed last year. Something
might have changed enough to throw the lock back on
since then. I was very lucky to find that my glazes
stood up for 3 years in outdoor weather of all kinds
and what you seen on my BLOG was those glazes except
for the washes and one experiment I had running. Over
the course of next month I will have 10-15 new
experiments all going on at the same time. I have them
ready on paper. I believe they will work just fine. I
learned what not to do at least. I am careful not to
over-use soluables for long term holding and large
batch mixing but I also find them neccessary under the
right set of circumstances. I did have one glaze that
wanted to show its butt but I know how to tame the
beast and use it in other ways.

Ulexite - Some of the newer materials used to sub GB
are based on this with a Sodium boron content. Your
getting a chemically similar material to GB that often
will spit and halo out around your materials.
Sometimes you will see other problems based on what
you added to your glaze to make it function to suit
you, sometimes it is going to work well for the long
haul and then suddenly turn around and bite you when
your in a rush to get to a show. Continue on in a
dogged fashion and test what you know you can use up
within a period of time if you are using certain
soluable materials. I believe this is why many see so
much shifting in several of the glaze recipes for
floating blue.

Off to the shelter. I needed some down-time myself and
this was a good workout to start my day.

Bill Edwards
Edmar Studio and Gallery
302 South Main St (Shipping)
POB 367 (Mailing)
Camp Hill, Al. 36850

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