Ben Shelton on sun 30 jul 06
Traditionally I have relied on specific gravity of the glaze slop, time and
trial and error to arrive at a methodlogy for applying glaze at the correct
thickness. I have seen posts by Mel and many others outlining the same
methodology.
I am wondering if there is a measuring method that approaches the question
from the opposite angle by measuring the actual thickness of the glaze once
applied???
I have been testing some shino type glazes and there are some real
interesting effects possible with multiple layering and resist techniques. I
just wondered if measuring the applied glaze layer would be helpful in this
case?
Ben
Hank Murrow on sun 30 jul 06
On Jul 30, 2006, at 5:06 AM, Ben Shelton wrote:
> I am wondering if there is a measuring method that approaches the
> question
> from the opposite angle by measuring the actual thickness of the glaze
> once
> applied???
DEar Ben;
You might try the method I use with my shinos which are very sensitive
to thickness.
I make graduated notches on one of the unsolicited credit cards that
come every week in the mail. Smaller notches to one end, larger towards
the other end. When you scrape the freshly glazed piece with the
notched edge of the card, the thickness is revealed. You can number the
notches so you have a reference thickness for your glazes.
Cheers, Hank
www.murrow.biz/hank
Lee Love on sun 30 jul 06
On 7/30/06, Ben Shelton wrote:
>
> I am wondering if there is a measuring method that approaches the question
> from the opposite angle by measuring the actual thickness of the glaze once
> applied???
Ben, the scratch test is a traditional method.
Measuring with a hydrometer, as you may have guessed, does not take
into account all variables and does not measure actual glaze
application thickness.
To help you train your eye, also use a test tile. Make sure
the tile is the same clay, bisque firing and thickness of the actual
pot. When you scratch the pot with your nail and you get a thickness
you think will work, dip and scratch the tile too. Number and
document both. Keep the tile. If it turns out well in the
firing, you now have an example of the thickness you are trying to
achieve.
I think glaze thickness variation is what makes shinos
interesting. But I don't like the really thick applications that are
currently popular here in Japan.
I am throwing mogusa clay right now. It is what shino was
traditionally put on. It is a porous clay, and is very light for its
thickness. I would like to develop a substitute folks could try
back home. I am guessing some very fine organic material would be
useful.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Ben Shelton on sun 30 jul 06
That is what I was wondering. It seems that for any given number of
variables such as bisque temp, clay porosity of different bodies, time in
the bucket etc you are trying to get a specific amount of glaze on the
surface. It seems that a test for that variable might help to narrow down
the search for proper application.
Several paint companies also make such test cards to test the application
thickness of their paint products. These cards are sometimes made of
stainless or aluminum and you drag them on a fresh coat of the paint and see
which notch the paint reaches. That is the coating thickness.
I also have seen mass used to determine glaze application. Put is weighed,
glazed, then weighed. Calculate to find a percent change in mass based on
the original. Compare to test results for a standard percent mass change.
I think we have some of those cards at work for one of the products we sell.
I'll see if I cant bag one and give it a try. It seems a really FAST on the
fly way to test.
Thanks, Ben
Lee Love on mon 31 jul 06
On 7/31/06, Ben Shelton wrote:
> That is what I was wondering. It seems that for any given number of
> variables such as bisque temp, clay porosity of different bodies, time in
> the bucket etc
Hydrometeres are only accurate at constant temperatures. I think I
saw 69*F. If they are a hollow tube, they are also effected by the
barometeric pressure.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Edouard Bastarache Inc. on mon 31 jul 06
Lee,
I use the nail of my right 5th finger to scratch
glazed pots
in order to appreciate the thickness of the glaze.
See, 5th finger is not only useful to drink tea.
Later,
Edouard Bastarache
Le Français 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/potier/172943983/
http://www.flickr.com/photos/potier/172941969/
catjarosz on mon 31 jul 06
Hi All,
I have not been following this one because I have been off Clay Art for a
few weeks. ( Had a fabulous show yippeee) but I have been chasing that
correct glaze application for yrs and yrs as it really affects everything to
do with my pots.
I basically turned into a control freak... Yes I know Clay has a way of
making us humble but for what its worth I try to control as much as
possible.
I do put self supporting 05's in every peep hole. This helps a lot but
I have 29" shelves so the middle part is a bit cooler and you have to try
and recognize bisque temp by color. Because I use a white stoneware clay
body I know that the pinker it comes out( from the middle) the more open the
body and more glaze it absorbs for the same hold count.. The whiter it
looks the less..
The Hydrometer I rinse under warm/hot water before I put it into the glaze
tub. Every time I do this.... I do believe the temp of your glaze affects
the results. You also need to try and feel the glaze and see what it looks
like on your hand / arm .
Lastly is the thickness of your work... I tend to throw my mugs and
goblets thinner than other pots and they take forever to dry along with a
scary scaly look to boot.. I have tried finger buffing and not finger
buffing and they come out fine either way..
Another factor is the size and manageability of the piece... Don't
underestimate that part.... if its big and heavy and glaze pools where I
cant shake it out as well or as fast I need to have a different plan of
action than one I do have better control over.
Which brings up another variable.. HOW you glaze the piece.. Do you have
liner glaze ... are you pouring or dipping just the outside and will you
have overlaps etc.. phew how on earth can you control EVERYTHING !!!
Its not easy and is one of the reasons it takes a lifetime to learn a
glaze...And I don't know that you can control EVERYTHING all the time.. but
every time you glaze hopefully you learn something new that will help. I
am sure I have left out plenty more variables . type of glaze is important
too.. forgiving or every drip shows up... that takes a different plan of
action..
Cat Jarosz in HUMID NC mountains.. spinning on head cause she is gonna
get NEW WINDOWS in her studio soon... Has a huge dumpster filled with
junk and could use it a few more times for all the car parts... the dump
truck project is almost all gone... bless my hubbys heart LOL... and
getting ready for the FIRST Leicester Artists Fall tour being held
Aug.19-20th.... I heard the web site is up and running...
www.cometoleicester.com (828)683-2459 ps that's pronounced Les-ter
not Lie -caster or Lee - sester.. Think England and not hooked on
phonics..
www.catjarosz.com
www.guildcrafts.com/cat/
V)''(V woof & >^..^< mew
(_o_)
\||/ chicks with beards rule!!
Russel Fouts on tue 1 aug 06
Hank,
>> I make graduated notches on one of the unsolicited credit cards
that come every week in the mail. Smaller notches to one end, larger
towards the other end. When you scrape the freshly glazed piece with
the notched edge of the card, the thickness is revealed. You can
number the notches so you have a reference thickness for your glazes. <<
Could you post a picture of one of these somewhere?
Thanks
Russel
Lee Love on tue 1 aug 06
On 7/31/06, Edouard Bastarache Inc. wrote:
> I use the nail of my right 5th finger to scratch
> glazed pots
> in order to appreciate the thickness of the glaze.
> See, 5th finger is not only useful to drink tea.
With your "pinky"? I use my index finger, because that is how I
saw it done at my teachers workshop. I cover the scratch with a dab
of glaze, usually on my pinky finger.
I had tea with my friends in England, every day about 3o'clock.
When we were out, we always got it with scones and Cornish clotted
cream and jam. They call it clotted cream because of what it does
to your arteriies, right? *Haha!* I was told, in Cornwall, you
put the cream on the scone first, and then the jam. But in Devon,
you put the jam on first and then the cream.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Ben Shelton on wed 2 aug 06
Here is what I have done.
I came to the conclusion that measuring the thickness of the dried layer of
glaze would be my benchmark and I should try to develop an application
method to duplicate an established result. We will see if this holds true in
testing.
Here is what I have done.
I had several bisqued "tiles" that I planned to put under glaze and clay
tests to catch any drips and runs. They are made of the same clay body that
I use and were cut into slabs and dried between drywall so thay are fairly
flat and equal in thickness. I waxed the edges and labeled them with red
iron oxide. Glaze was then applied varying from thin to thick and allowed to
dry. The glaze was scraped off down the middle of the tile about 3/16" wide.
I used my dial caliper to measure the thickness at various points along this
scraped trough and wrote them on the tile in iron oxide. Most varied from
0.008"~0.025"
Now I can fire them and get a better idea of a glaze thickness of
application to shoot for. I can then adjust my application methods to yield
a desired thickness of application (in theory as long as the firings are
consistant)
Anyway, that's what you get when you cross an over analytical science type
with a love for clay and glazes.
I'll keep you posted when the test tiles get fired.
Ben
Lee Love on wed 2 aug 06
Way to go Ben! Let us know how your new method turns out.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
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