Lee Love on sun 5 aug 07
On 8/5/07, Timothy Joko-Veltman wrote:
> A more technical method of determining wet glaze thickness is to
> measure its relative density.
This might not give you an accurate thickness of applied glaze
because of a number of variables, including type of clay body and
actual hardness of the bisque.
The most accurate way to measure glaze application thickness
is by scratching the glaze and actually measuring the thickness of the
glaze. Density can give you a ballpark place to start, but doing
tests on sample pieces of bisque first, and then the actual bisque
that is going to be glazed, is the most accurate.
In the beginning, you can label and record you scratch tests
and then compare your glazing to the test tile. It takes "eye
training" to become accurate, but it comes with time and experience.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Lili Krakowski on sun 5 aug 07
Cathy:
You write:
".... I don't want to make a mess of my first glaze
firing!...
1) I bisque fired to cone 06, and am finding that my glazes are not
absorbing well.
2) I want to apply two colors of glaze to a square plate that I made.
I do assume that the best way to do this would be to first dip the plates in
the black glaze,
then use some sort of wax to mask the edge of black I want to protect, and
then use a
brush to paint on the yellow glaze."
My first reaction was/is: So, do you want to make a mess of your second
firing?
I am not being cruel, I am being bluntly honest. If you are going to pot
then you are going to have terrible firings.
Both archives and weepy potters at the Ramshead Pub will tell you that
perhaps 5% of disasters are Acts of God, things that happen. The rest are
the result of impatience, inexperience, and the refusal to take things one
at a time.
Having said that you don't tell us what your glaze temperature is. If it
c.6 then c.06 seems ok as a bisquing temp. If you are doing earthenware
then 06 is too high, and I would ask the dealer what you are to bisque at.
If St Teresa of Avila said that more tears are shed for answered prayers
than for unanswered ones, I say more tears are shed by Newbies from
confusing the cones that start with 0 and the ones that don't.
Hermann Seger who invented cones started out with Cone 1. They started at 1
and went UP (hotter). He then found he needed cones that were "cooler" than
1 so he made the cones prefaced by 0--such as c.01,02 etc. These get
COOLER, they go DOWN as their number rises.
So. C.2 is "hotter" than c.1, and c.6 is hotter than c.2. On the other
hand c01 is hotter than c.02, and c02 is hotter than 06. (I gave myself a
headache typing this.)
If you find that the body does not absorb properly you may be bisquing too
high for it. On the other hand you may have mixed your glaze too thin.
Ivor spoke of single cream and double cream the other day....in US terms
light cream and heavy cream, though I do not know how fat % compare,)
Not all glazes are ideal at the same thickness....so a dime seems really
thin to me. The thickness between a nickel and a quarter more likely.
Now as to your second question. You are on the right track. The suppliers
sell different wax emulsions and the archives will tell you some potters use
acrylic painting mediums. The wax emulsions work well. Applying them
properly, especially if you want sharp edges, takes practice. You might try
making a newspaper stencil to block out the part you do not want to paint
yellow. AND you have to remember that a double coat of glaze is a double
coat--if you have a very fluid glaze it may form a sort of puddle effect. No
idea. Just watch out. AND TEST.
I strongly strongly strongly suggest that you make tests first. That you
make yourself some test tiles and test your ideas on them first. That you
keep records of how thickly you applied the glaze to the tile, how thick the
glaze itself was, and so on.
That for double application you use flat test tiles (leave a good margin
unglazed, or make them with a little rim) and try different applications
first.
Welcome to the club, welcome to the Pub. Good luck
Lili Krakowski
Be of good courage
Tom at Hutchtel.net on sun 5 aug 07
Subject: Newbie glaze questiions
> Cathy:
>
> high for it. On the other hand you may have mixed your glaze too thin.
> Ivor spoke of single cream and double cream the other day....in US terms
> light cream and heavy cream, though I do not know how fat % compare,)
Cathy, one of the traditional test for the thickness of the glaze in the
bucket is to dip in a finger to cover the nail. You should still be able to
see the outline of the nail, but if you can see any detail, the glaze is too
thin. Let it settle and take some water off the top.
This is only a very rough rule of thumb, and will vary glaze to glaze, but
it is a starting point without going to instruments and weighing for
specific gravity/density.
Tom Wirt
Timothy Joko-Veltman on sun 5 aug 07
On 8/5/07, Tom at Hutchtel.net wrote:
> Cathy, one of the traditional test for the thickness of the glaze in the
> bucket is to dip in a finger to cover the nail. You should still be able to
> see the outline of the nail, but if you can see any detail, the glaze is too
> thin. Let it settle and take some water off the top.
>
A more technical method of determining wet glaze thickness is to
measure its relative density. This is actually easy to do, and in my
opinion will give you more reliable and repeatable glaze thickness.
Get a graduated cylinder (or even just a measuring cup), weigh it (or
set the tare on your scale with the cylinder/measuring cup on it.
Then pour out a fixed amount of the well-stirred glaze into it.
Always use the same amount. 100ml is most convenient, but 1 cup would
work just as well, so long as you always work with the same measure
(put it aside and mark it you so never forget). Record the weight.
If you used 100ml, this number is the "specific density" the jargon
for its density relative to water. If you used a different measure,
you can still find the specific gravity, but it's a bit more
complicated. As I said, record this weight. On the test tile is not
a bad idea. If you wish to test a lower density, add some water to
the glaze, stir it up, and repeat.
Once you've found the density you like for a particular glaze, stir
the glaze and weigh it each time before you use it, and if you find it
is too high (because probably a bit of water evaporated off) add water
a little at a time until you get the right thickness. I suppose this
might sound like a pain in the buttocks, but you will be able to glaze
knowing that the wet glaze is very close to exactly the same
thickness/density it was last time you used it.
Regards,
Tim
artist0267 on mon 6 aug 07
Thank you all for your help. I have actually ordered a hydrometer, which I =
think will really
help me tell how much water to add to my glazes. I think I just bought way =
too little dry
glaze, and then added way too much water!
I don't think I overfired the bisque, since I am going to glaze fire up to =
cone 5--so the
bisque should be fired to cone 06. I'm quite sure that is correct. Please t=
ell me if I am
wrong.
Nobody did tell me what to do about how to apply the wax over the unfired g=
laze when I
want to abut the second color next to the black. Do I want to end the wax r=
ight at the
place where the black ends, or do I want the yellow to overlap the black a =
little bit so that I
do not have any bare clay at the seam.
Thank you,
Cathy
--- In clayart@yahoogroups.com, Lili Krakowski wrote:
>
> Cathy:
>
> You write:
>
>
> ".... I don't want to make a mess of my first glaze
> firing!...
>
> 1) I bisque fired to cone 06, and am finding that my glazes are not
> absorbing well.
>
> 2) I want to apply two colors of glaze to a square plate that I made.
> I do assume that the best way to do this would be to first dip the plates=
in
> the black glaze,
> then use some sort of wax to mask the edge of black I want to protect, an=
d
> then use a
> brush to paint on the yellow glaze."
>
> My first reaction was/is: So, do you want to make a mess of your second
> firing?
>
> I am not being cruel, I am being bluntly honest. If you are going to pot
> then you are going to have terrible firings.
> Both archives and weepy potters at the Ramshead Pub will tell you that
> perhaps 5% of disasters are Acts of God, things that happen. The rest ar=
e
> the result of impatience, inexperience, and the refusal to take things on=
e
> at a time.
>
> Having said that you don't tell us what your glaze temperature is. If i=
t
> c.6 then c.06 seems ok as a bisquing temp. If you are doing earthenware
> then 06 is too high, and I would ask the dealer what you are to bisque at=
.
> If St Teresa of Avila said that more tears are shed for answered prayers
> than for unanswered ones, I say more tears are shed by Newbies from
> confusing the cones that start with 0 and the ones that don't.
>
> Hermann Seger who invented cones started out with Cone 1. They started a=
t 1
> and went UP (hotter). He then found he needed cones that were "cooler" t=
han
> 1 so he made the cones prefaced by 0--such as c.01,02 etc. These get
> COOLER, they go DOWN as their number rises.
>
> So. C.2 is "hotter" than c.1, and c.6 is hotter than c.2. On the other
> hand c01 is hotter than c.02, and c02 is hotter than 06. (I gave myself a
> headache typing this.)
>
> If you find that the body does not absorb properly you may be bisquing to=
o
> high for it. On the other hand you may have mixed your glaze too thin.
> Ivor spoke of single cream and double cream the other day....in US terms
> light cream and heavy cream, though I do not know how fat % compare,)
>
> Not all glazes are ideal at the same thickness....so a dime seems really
> thin to me. The thickness between a nickel and a quarter more likely.
>
> Now as to your second question. You are on the right track. The supplie=
rs
> sell different wax emulsions and the archives will tell you some potters =
use
> acrylic painting mediums. The wax emulsions work well. Applying them
> properly, especially if you want sharp edges, takes practice. You might =
try
> making a newspaper stencil to block out the part you do not want to paint
> yellow. AND you have to remember that a double coat of glaze is a double
> coat--if you have a very fluid glaze it may form a sort of puddle effect.=
No
> idea. Just watch out. AND TEST.
>
> I strongly strongly strongly suggest that you make tests first. That yo=
u
> make yourself some test tiles and test your ideas on them first. That yo=
u
> keep records of how thickly you applied the glaze to the tile, how thick =
the
> glaze itself was, and so on.
> That for double application you use flat test tiles (leave a good margin
> unglazed, or make them with a little rim) and try different applications
> first.
>
>
> Welcome to the club, welcome to the Pub. Good luck
>
>
>
>
> Lili Krakowski
> Be of good courage
>
> _________________________________________________________________________=
_____
> Send postings to clayart@...
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@...
>
Frank Gaydos on mon 6 aug 07
Cathy,
I mix all our galzes at the Community College of Philadelphia.
I just add water till it is the thickness of milk.
I also dip my fingers in the glazes and it is just right if I see the hair
on my fingers, but the rest of my finger is covered..
Good luck
Frank
----- Original Message -----
From: "artist0267"
To:
Sent: Monday, August 06, 2007 4:28 PM
Subject: Re: Newbie glaze questiions
Thank you all for your help. I have actually ordered a hydrometer, which I
think will really
help me tell how much water to add to my glazes. I think I just bought way
too little dry
glaze, and then added way too much water!
I don't think I overfired the bisque, since I am going to glaze fire up to
cone 5--so the
bisque should be fired to cone 06. I'm quite sure that is correct. Please
tell me if I am
wrong.
Nobody did tell me what to do about how to apply the wax over the unfired
glaze when I
want to abut the second color next to the black. Do I want to end the wax
right at the
place where the black ends, or do I want the yellow to overlap the black a
little bit so that I
do not have any bare clay at the seam.
Thank you,
Cathy
--- In clayart@yahoogroups.com, Lili Krakowski wrote:
>
> Cathy:
>
> You write:
>
>
> ".... I don't want to make a mess of my first glaze
> firing!...
>
> 1) I bisque fired to cone 06, and am finding that my glazes are not
> absorbing well.
>
> 2) I want to apply two colors of glaze to a square plate that I made.
> I do assume that the best way to do this would be to first dip the plates
> in
> the black glaze,
> then use some sort of wax to mask the edge of black I want to protect, and
> then use a
> brush to paint on the yellow glaze."
>
> My first reaction was/is: So, do you want to make a mess of your second
> firing?
>
> I am not being cruel, I am being bluntly honest. If you are going to pot
> then you are going to have terrible firings.
> Both archives and weepy potters at the Ramshead Pub will tell you that
> perhaps 5% of disasters are Acts of God, things that happen. The rest are
> the result of impatience, inexperience, and the refusal to take things one
> at a time.
>
> Having said that you don't tell us what your glaze temperature is. If it
> c.6 then c.06 seems ok as a bisquing temp. If you are doing earthenware
> then 06 is too high, and I would ask the dealer what you are to bisque at.
> If St Teresa of Avila said that more tears are shed for answered prayers
> than for unanswered ones, I say more tears are shed by Newbies from
> confusing the cones that start with 0 and the ones that don't.
>
> Hermann Seger who invented cones started out with Cone 1. They started at
> 1
> and went UP (hotter). He then found he needed cones that were "cooler"
> than
> 1 so he made the cones prefaced by 0--such as c.01,02 etc. These get
> COOLER, they go DOWN as their number rises.
>
> So. C.2 is "hotter" than c.1, and c.6 is hotter than c.2. On the other
> hand c01 is hotter than c.02, and c02 is hotter than 06. (I gave myself a
> headache typing this.)
>
> If you find that the body does not absorb properly you may be bisquing too
> high for it. On the other hand you may have mixed your glaze too thin.
> Ivor spoke of single cream and double cream the other day....in US terms
> light cream and heavy cream, though I do not know how fat % compare,)
>
> Not all glazes are ideal at the same thickness....so a dime seems really
> thin to me. The thickness between a nickel and a quarter more likely.
>
> Now as to your second question. You are on the right track. The
> suppliers
> sell different wax emulsions and the archives will tell you some potters
> use
> acrylic painting mediums. The wax emulsions work well. Applying them
> properly, especially if you want sharp edges, takes practice. You might
> try
> making a newspaper stencil to block out the part you do not want to paint
> yellow. AND you have to remember that a double coat of glaze is a double
> coat--if you have a very fluid glaze it may form a sort of puddle effect.
> No
> idea. Just watch out. AND TEST.
>
> I strongly strongly strongly suggest that you make tests first. That you
> make yourself some test tiles and test your ideas on them first. That you
> keep records of how thickly you applied the glaze to the tile, how thick
> the
> glaze itself was, and so on.
> That for double application you use flat test tiles (leave a good margin
> unglazed, or make them with a little rim) and try different applications
> first.
>
>
> Welcome to the club, welcome to the Pub. Good luck
>
>
>
>
> Lili Krakowski
> Be of good courage
>
> ______________________________________________________________________________
> Send postings to clayart@...
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@...
>
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Terrance Lazaroff on tue 7 aug 07
Kathy;
Once you have gone about mixing your glazes and then recording the density
and or looking at your finger, remember you have to document your signs of
when the glaze is going to be just right.
The best method I found to determine the thickness of glaze is buy using
the same system used by photographers when working in the dark room trying
to determine the best time for the best contrast. They expose portions of
the photo paper about an inch at a time allowing a set time for each
exposure. They then choose the exposure time of the strip showing the best
contrast.
In glazing you make a series of tall 6 to 8 inch cylinders, let them dry
and then bisque them.
When you have strained your glaze, (I usually strain my glaze three times
through 99 grid screen) and recorded the statistics, take one of the
cylinders and dip it about an inch into the glaze mix and count one one-
thousand, two one-thousand and then continue to push the cylinder down into
the glaze another inch repeating the two one-thousand count and then push
another inch and count again, doing this four times or until you make a
cumulative count of eight one-thousands.
If you push the cylinder approximately one inch each time you will have
four one inch bands of different thickness glazes. Standing the cylinder
upright for firing you can see that the band at the top of the cylinder had
a count of eight one-thousand as it was in the glaze from the start, the
next band down would be six one-thousand, the next four one-thousands and
the bottom one would be two one-thousand. I leave a large thickness of
unglazed cylinder at the bottom so that there will be a safety should the
glaze be too fluid in the firing.
Fire this cylinder and look at the results and you will be able to
determine how long to dip your future pots into the glaze when it is at the
same density or weight as it was when the test cylinder was taken.
Terrance
Visit Terry's web site at http://clayart.ca
John Sankey on tue 7 aug 07
Lee Love: "The most accurate way to measure glaze application
thickness is by scratching the glaze and actually measuring the
thickness of the glaze. Density can give you a ballpark place to
start, but doing tests on sample pieces of bisque first, and then
the actual bisque that is going to be glazed, is the most
accurate."
I agree totally with Lee. If you want to control glaze thickness,
measure glaze thickness if you can, not a secondary property like
specific gravity of a glaze solution. See
http://sankey.ws/pottery.html
about 90% of the way down the page for an accurate way of doing
it.
--
(Add 'Byrd' to the subject line of your reply to get through my spam filter)
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