search  current discussion  categories  glazes - chemistry 


updated mon 8 mar 04


Vince Pitelka on fri 8 may 98

Not meaning to start the same old argument about the accuracy of
hydrometers, but I found a beauty in the VWR Scientific catalog - their
webpage is - phone is 800/932-5000. It is reasonably priced,
and is designed specifically for testing small volumes of heavy liquids.
The hydrometer is 6.5" (165mm) long, has a s.g. scale from 1.00 to 2.00, and
costs $19.97 each - cat. #34640-207.
- Vince

Vince Pitelka -
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166

Bill Aycock on mon 8 oct 01

The question of Hydrometers keeps coming up. If you are working with
Terra-Sig, take Vinces advice, which is for a lower range device. If you
are working with glazes- DO NOT use a hydrometer.

In reply to some questions some years ago on Clayart- I made some
recommendations, based on Lab experience. I was called on it, so- I made a
large series of tests. The short answer is that a glaze that is thick
enough for most applications will NOT measure well on a hydrometer.

I used several different types of glaze, from so thin they settled, to some
that almost gelled. Any that were workable by dip, brush, or spray, could
be tweaked to give a wide range of specific gravity values with a
Hydrometer. in other words- the reproducibility of the measurements was zilch.

The same glazes could be measured very easily with a paper cup and beam
balance. Simple process- fill the cup with water- weigh it- dump the
water- fill the cup with glaze- weigh it. The ratio of the two weights is
the SpG. You can get a LOT of paper cups for the price of a Hydromeer that
wont do the job as well, or at all.

Bill - on Persimmon Hill, where fall has arrived. The next show will be the
annual fermented persimmon party, wherein the Raccoons get looped and drive
the dogs wild.
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr

artimater on mon 8 oct 01

Or you stick your hand in there .....If it coats your fingernail and =
looks like think cream when it pores it's about right, right?

"I only indulge when I've seen a snake, so I keep a supply of =
indulgences and snakes handy"

Tony Ferguson on tue 9 oct 01

I use the glove test--stick your finger in--if you can
see your finger prints--it's too thin--of course if
you don't have any because you just robbed a bank or
you throw with pee grog like me, then you're out of

Tony Ferguson Duluth, MN

Tony Ferguson
Shino & Ash Stoneware & Porcelain, Raku
(218) 727-6339

claybair on tue 9 oct 01

Rush's fingernail test may not work for all glazes.
The glazes I have used have a range from the light cream coated fingernail,
to regular milk with visible fingernail, to skim milk. So you can go the
trial and error and testing route or hydrometer route.
Scientist or seat of the pants.

Gayle Bair... a seat of the pants girl but if I ever see someone demo a
hydrometer I might be converted!
Bainbridge Island, WA

Or you stick your hand in there .....If it coats your fingernail and looks
like think cream when it pores it's about right, right?

"I only indulge when I've seen a snake, so I keep a supply of indulgences
and snakes handy"

Send postings to

You may look at the archives for the list or change your subscription
settings from

Moderator of the list is Mel Jacobson who may be reached at

Patti Kratzke on tue 9 oct 01

If anyone is still looking for a hydrometer, Seattle Pottery actually has
two kinds: one that is supposed to work for both glaze and slip, and one
that's specially for slip. I got the dual-use one (cost around $20) and
I tested the calibration with known substances, and it was fairly
accurate. The just-for-slip one costs a bit more, perhaps $25. They
have a web site to order from (again - no I
don't work for them - they're just great folks!), and they ship, in case
you're not in the area (although I'd hate to have the thing break in
transit). They might also be able to tell you if anyone in your area
carries these. My problem has been when I work in small quantities,
getting the slip into something that makes it to be deep enough for the
hydrometer to not hit bottom! So I might try the weighing method myself
in those situations.

Patti Kratzke
Kingston, WA
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:

lili krakowski on sun 7 mar 04

Whether you should use hydrometers or not depends on a number of =
things...For instance I have used them only in group classroom =
situations where people who do not have the feel of a proper consistency =
for a particular glaze in their fingers need help in diluting or trying =
to dry out glaze buckets. I have used h. for slips.

(Modestly she adds that in July/August 2002 PMI she had a little article =
on hydrometers)

I like to take a narrow pill bottle about 3 inches long and place a =
weight in it. A little stone, cement, small chards, fishing weights. I =
place the cap on and adjust the weight to where the bottom of the cap =
sits just atop the fluid when the fluid is the right consistency.

I then glue the weights in, being careful to double check the glue does =
not add weight--and glue the lid on. Mark each pillbottle with the name =
of "its" glaze.

Also fun is to make clay beads with the hole big enough to be "threaded" =
on a chopstick or an old knitting needle (thrift shop)

Glue a bottom bead (the retaining one) in place. When the glue is dry, =
add beads atop, till the chopstick sinks respectably into your glaze. =
Mark the spot with a notch. Voila. Glue all the beads into place. =
Ideally you will have glazed one bead with the glaze in question, be =
able to identify each hydrometer by its glaze bead.

Lili Krakowski

Be of good courage