Susan L. Ross on sat 8 nov 97
Would anyone out there mind sharing with me how to use a hydrometer?
Thanks a mil :-)
Su
Potting in Piedmont, CA
After a refreshing rain...
RubySuMoon@aol.com
Greg Lamont on sun 9 nov 97
Hi Su,
Here's what I've learned about hydrometers, so far. Others may correct me
if I'm off base here. They're good for testing the specific gravity of
solutions to be sure they're properly composed and mixed. In the case of
glazes--that the water content is where it should be--not too thick or too
thin. Hydrometers can be used to measure consistency from batch to batch by:
1. Pour a quantity of thoroughly mixed glaze into a deep enough container
(I use a 2 liter pop bottle with the neck cut off),
2. Wet the hydrometer with water and gently drop it into the glaze. Here
in the studio, our glazes are diluted to a reading in the hydrometer of
between 1400 (1.4) and 1600 (1.6)
That said, here's what glaze guru Pete Pinnell told me at a workshop a year
or so ago. The problem with hydrometers is that they're designed for
measuring solutions not suspensions. Glazes, terra sigs, etc. are
suspensions. His method is to:
1. Take a see-through container--I use a clear plastic cup--and carefully
measure out 100 grams of water on your gram scale.
2. Using a fine-tip permanent marker, carefully mark the level of the water
on the cup, then empty and refill to that mark with glaze.
3. Reweigh and note the difference, then divide by 100. The difference is
the amount of solid material in suspension in the glaze. If, for example,
the glaze-filled cup weighs 140 grams, that would be 1.4. If it weighs,
say, 180 grams (1.8), that might mean the glaze is too thick and would need
to be thinned out. If it weighs 1.2, the glaze might be too thin and need
to be allowed to settle and some of the excess water drawn off. It's a more
time-consuming method, but, I'm told, more accurate. You might try using
this method the first time a paarticular batch of a glaze is mixed, then,
when you've found the viscosity that's right for your application methods,
measure it withthe hydrometer and use the hydrometer's measurement to
compare future batches.
Hope this helps,
Greg
At 05:27 PM 11/8/97 EST, you wrote:
>----------------------------Original message----------------------------
>Would anyone out there mind sharing with me how to use a hydrometer?
>
>Thanks a mil :-)
>
>Su
>Potting in Piedmont, CA
>After a refreshing rain...
>RubySuMoon@aol.com
>
Vince Pitelka on sun 9 nov 97
>Would anyone out there mind sharing with me how to use a hydrometer?
>Su
>Potting in Piedmont, CA
Su -
This depends on what kind of hydrometer you have, and what you are going to
use it for. The hydrometer must be one intended for use in liquids ranging
from the weight of water up to twice the weight of water. A winemaker's
hydrometer will not work, because it measures liquids lighter than water.
With a mixture of ceramic materials in suspension, if the specific gravity
is any higher than twice that of water, viscosity and friction prevent a
floating hydrometer from working anyway. In use, the clean, dry hydrometer
is simply immersed in the liquid, and then released to find it's level. The
scale is read exactly at the point where the hydrometer emerges from the
liquid once it has stopped bobbing. With a thicker mixture it is sometimes
hard to read the scale, but once the hydrometer stops bobbing and finds its
level, you can lightly mist the scale where it emerges from the glaze/slip
with a bit of water, and it will clear up the scale without altering the
reading.
From previous discussions on the list it is clear that there is a lot of
variation in available hydrometers. Some just have a number scale which
does not relate to actual specific gravity. Some would say that is best,
since it is hard to get a really accurate specific gravity (weight per
volume in comparison to that of water) measurement with a hydrometer unless
you know your instrument very well. With a hydrometer which has a number
scale, you simply measure the RELATIVE specific gravity of a known entity -
such as a slip or glaze which works well, and then use the hydrometer to
achieve the same relative specific gravity in subsequent batches.
My own hydrometers were purchased out West at least 20 years ago. I bought
one, and the first time I used it I shook it off, and broke it. The
experience taught me that in order to work, the glass in the upper portion
of a hydrometer must be VERY thin. So I ordered two more of them, and I
still have both of them (this is one standard way to defeat Murphy's law.
Have an extra of everything.). They have a simple number scale on one side,
and on the other side a scale which relates to the weight of water. In
other words, when immersed in pure water, the hydrometer levels at 1.0. In
a liquid twice as heavy as water it should level at 2.0. It doesn't always
work that way, however, because of the friction involved with a thicker
liquid. But I have had excellent luck using my hydrometer in slips and
glazes ranging from 1.1 S.G. to 1.8.
Good luck.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
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
cen00541@mail.wi.centuryinter.net on sun 9 nov 97
I have come to rely on the use of my hydrometer to such an extent
that at this time I wouldn't even consider glazing without one. It's
use is very simple:
1. Mix and screen your glazes as you normally would.
2. Wet the hydrometer with water and gently release it into the
glaze.
3. Read the number from the scale on the hydrometer.
If your glaze has been mixed to a consistency that has given you
good results continue to mix the glaze material/water ratio to
achieve the same reading on the hydrometer. Thinning the glaze by
adding more water will result in a lower reading on the scale,
conversely removing some of the water content will raise the reading.
Most of the glazes that I use give readings that fall somewhere
between 1450 and 1400. This gives me a good mix for a double dip or
double pour glaze application.
Bill Karaffa
Firemouth Pottery and Gallery
4384 Hwy.51 N
Boulder Jct. Wi 54512
Studio: 715-385-2889 Gallery: 715-385-2810
Bill Karaffa
Firemouth Pottery and Gallery
4384 Hwy.51 N
Boulder Jct. Wi 54512
Studio: 715-385-2889 Gallery: 715-385-2810
Ray Carlton on mon 10 nov 97
hi sue a hydrometer tells you the density of material in water//for our
purposes how much glaze is in a given volume of water or how much will
stick to a pot in a given amount of time. in other words how thick the
glaze is.
it is usefull to keep the glaze consistency hmmm consistent so you get the
same thickness of it on your pot each time you dip. it is very simple to
use/ you just put it gently in your favorite glaze and read the number it
stops at. Next time you make up the glaze add water until the hydrometer
reads the same and presto your glaze is the same every time
cheers
At 05:27 08/11/97 EST, you wrote:
>----------------------------Original message----------------------------
>Would anyone out there mind sharing with me how to use a hydrometer?
>
>Thanks a mil :-)
>
>Su
>Potting in Piedmont, CA
>After a refreshing rain...
>RubySuMoon@aol.com
>
>
raycarlt@valylink.net.au
Ray Carlton
McMahons Creek Victoria Australia 3799
Bill Aycock on tue 11 nov 97
Last year, when this thread came up, I ran a series of tests to back up my
(then) position about hydrometers and specific gravity. I proved, to my
satisfaction, that I was VERY WRONG. What I did then was called
"crawfishing", in Louisisana, where it means backing up, usually fast.
Simply- the results of my tests showed that a hydrometer was VERY
MISLEADING for the range of specific gravities of most glazes and slips.
When you are in the range of values of Terra Sigilata, as Vince makes, they
work pretty well, but for suspensions above about 1.2, 1.3, they are not at
all accurate.
I could get readings that ranged over a wide span, depending on how fast or
slowly I inserted the instrument. the use of fluculants or de-floculants
only exagerated the effect..
The method recommended by Jonathan (weighing a standard container) works
very well. However, one caveat about his posting- ** Do NOT trust that "a
pints a pound, the world around" **- weigh the container you use with
water, and with your slip or glaze, to be sure YOUR pint is what it is
supposed to be. If you want real accuracy, weigh your container empty, then
with water, then with your suspension. Subtract the weight of the
container from the other weighings, to get the weight of the water and the
stuff you are interested in. The ratio of those weights is what you want,
and it doesnt matter whether its a pint, a cup, or a gallon, so long as
both volumes are the same.
and- KEEP NOTES-- it helps next time.
Bill - weighing ponderous matters, on Persimmon Hill.
Bill Aycock --- Persimmon Hill --- Woodville, Alabama, US 35776
--- (in the N.E. corner of the State) ---
W4BSG -- Grid EM64vr --
baycock@hiwaay.net
Erin Hayes on tue 11 nov 97
I can't remember who started this hydrometer thread, but I wanted to add
my wholehearted approval of their use.
It is especially helpful when you have glazes that perform best when
they are at very specific densities. We have a turqouise matt that is
divine at 1.7 (kinda gloppy) and a clear that only behaves at 1.3 (kinda
thin). With a hydrometer, we can measure the specific gravity of the
glaze when it is behaving really well, and benchmark the glaze. From
that point on the guesswork is taken out of the equation - always a
plus.
Erin.
Roger Korn on thu 13 nov 97
Vince wrote:
...So I ordered two more of them, and I
>still have both of them (this is one standard way to defeat Murphy's law.
>Have an extra of everything.).
I have about four tape measures. When I can't find any of them, I buy a new
one. The next day, I will immediately find the other four.
>... But I have had excellent luck using my hydrometer in slips and
>glazes ranging from 1.1 S.G. to 1.8.
When my wife returned from Vince's Ancient Clay Workshop, she wanted a
glaze hydrometer. I showed her how to calculate SG by weighing a known
volume, but it was cumbersome for her. I got a glaze hydrometer and somehow
my own glazes got a lot more consistent. Funny, how making a process a
little easier can yield a lot better results.
Roger, in North Plains, OR where the leaves are falling into the reduction
containers.
M Richens on thu 13 nov 97
In article <346746CB.4B482C89@ctc.edu>, Erin Hayes
writes
>----------------------------Original message----------------------------
>I can't remember who started this hydrometer thread, but I wanted to add
>my wholehearted approval of their use.
>
>It is especially helpful when you have glazes that perform best when
>they are at very specific densities. We have a turqouise matt that is
>divine at 1.7 (kinda gloppy) and a clear that only behaves at 1.3 (kinda
>thin). With a hydrometer, we can measure the specific gravity of the
>glaze when it is behaving really well, and benchmark the glaze. From
>that point on the guesswork is taken out of the equation - always a
>plus.
>
>Erin.
Hi Erin,
This is where hydrometers fall down. The slip has to be _FULLY_
deflocculated and runny. If you have set it rigid with Calcium Chloride
at a 1.45 SG then you won't get the hydrometer in to measure the SG
accurately.
Max
--
Max Richens max@richens.demon.co.uk +44 (0) 1925756241
Enamel Consultant - Ceramist - Analyst programmer
Software for Batch Formulation and Millroom control.
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