Des Howard on tue 9 oct 01
John
I agree using a hydrometer in clay or glaze slips/slurries will
give you imprecise readings. But!
The imprecision is repeatable to a precise degree.
I guess it depends whether you are doing research for publication
or you just want the glaze, etc., to match up to the last time
you used the hydrometer to adjust the grams/cc or ozs/pint, whatever,
note I didn't say specific gravity.
For years we used a stumpy thermometer with the bulb
epoxied into a 9 mm shell case, stir the glaze, pop in the whatsit,
take a reading, add water, repeat until spot on the required reading,
who cares that the readings we took were gibberish,
it was repeatable gibberish.
Another example of repeatable gibberish is our glaze dip times,
I count silently, "hippopotamus 1, hippopotamus 2, hippopotamus 3,
hippopotamus 4, hippopotamus 5, hippopotamus 6", so does Trev.
For years I've said he dips for a count of 5,
he swears I dip for a count of 7. Check out "Rhythm of Life" in
New Scientist 4 Aug. 2001, all about internal metronomes.
Guess what? We both get the same thickness of glaze on the pot.
Regards
Des
John Hesselberth wrote:
> Hi Jim,
>
> You might reconsider whether or not you really want a hydrometer. If you
> are using it for clay or glaze slips/slurries, hydrometers are notoriously
> imprecise for suspensions. They work OK for single phase materials. Rather
> get yourself a 100 ml graduated cylinder and weigh 100 ml of your
> glaze/slip. It will be much more precise, just as accurate and just about
> as simple.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Bill Aycock on tue 9 oct 01
At 11:42 PM 10/9/01 +1000, you wrote:
>John
>I agree using a hydrometer in clay or glaze slips/slurries will
>give you imprecise readings. But!
>The imprecision is repeatable to a precise degree.
>I guess it depends whether you are doing research for publication
>or you just want the glaze, etc., to match up to the last time
>you used the hydrometer to adjust the grams/cc or ozs/pint, whatever,
>note I didn't say specific gravity.
>
>
My tests say this is hogwash. I was able to get a wide range of readings
with one container of glaze- no changes- by pushing the instrument down, or
lifting it up. Many glazes are thick (ie, high viscosity) enough to make
any flotation device useless.
BTW- the phrase "imprecision is repeatable to a precise degree." is pure
nonsense.
Bill- On Persimmon Hill, where symantics rules!
-
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
w4bsg@arrl.net
Des Howard on wed 10 oct 01
Bill
I'm sorry your tests did not work. The technique works for us in
our production glazes & is repeatable to a precise degree.
I am a better potter than I am a linguist
Des
BTW- semantics doesn't rule here but correct spelling does
D
Bill Aycock wrote:
> At 11:42 PM 10/9/01 +1000, you wrote:
> >John
> >I agree using a hydrometer in clay or glaze slips/slurries will
> >give you imprecise readings. But!
> >The imprecision is repeatable to a precise degree.
> >I guess it depends whether you are doing research for publication
> >or you just want the glaze, etc., to match up to the last time
> >you used the hydrometer to adjust the grams/cc or ozs/pint, whatever,
> >note I didn't say specific gravity.
> >
> >
> My tests say this is hogwash. I was able to get a wide range of readings
> with one container of glaze- no changes- by pushing the instrument down, or
> lifting it up. Many glazes are thick (ie, high viscosity) enough to make
> any flotation device useless.
>
> BTW- the phrase "imprecision is repeatable to a precise degree." is pure
> nonsense.
>
> Bill- On Persimmon Hill, where symantics rules!
> -
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Christena Schafale on wed 10 oct 01
I wonder if the explanation might lie in the fact that Des' glazes have, as
he reports, little or no clay in them. My experience suggests that the
"gelled" quality of high-clay glazes (or glazes with the late unlamented
GB) is partly responsible for faulty hydrometer readings. What do you think?
By the way, Des, why do you eliminate the plastic materials from your
glazes? And do you use something to keep them suspended without clay?
Chris
At 06:44 PM 10/10/01 +1000, you wrote:
>Bill
>I'm sorry your tests did not work. The technique works for us in
>our production glazes & is repeatable to a precise degree.
>I am a better potter than I am a linguist
>Des
>
>BTW- semantics doesn't rule here but correct spelling does
>D
>
>Bill Aycock wrote:
>
> > At 11:42 PM 10/9/01 +1000, you wrote:
> > >John
> > >I agree using a hydrometer in clay or glaze slips/slurries will
> > >give you imprecise readings. But!
> > >The imprecision is repeatable to a precise degree.
> > >I guess it depends whether you are doing research for publication
> > >or you just want the glaze, etc., to match up to the last time
> > >you used the hydrometer to adjust the grams/cc or ozs/pint, whatever,
> > >note I didn't say specific gravity.
> > >
> > >
> > My tests say this is hogwash. I was able to get a wide range of readings
> > with one container of glaze- no changes- by pushing the instrument down, or
> > lifting it up. Many glazes are thick (ie, high viscosity) enough to make
> > any flotation device useless.
> >
> > BTW- the phrase "imprecision is repeatable to a precise degree." is pure
> > nonsense.
> >
> > Bill- On Persimmon Hill, where symantics rules!
> > -
>
>--
>
>Des & Jan Howard
>Lue Pottery
>LUE NSW 2850
>Australia
>Ph/Fax 02 6373 6419
>http://www.luepottery.hwy.com.au
>
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Martin Howard on wed 10 oct 01
Christena is probably right from my experience.
As I use a lot of cat litter, Bentonite/Montmorrilonite, in my homemade
glazes, those glazes are very difficult to assess with the hydrometer.
So,I use the weighing method for those.
It is very accurate, as far as my homemade hydrometer is accurate! for those
bought glazes that have virtually no clay in them.
But the finger method is also very useful.
Another quick method is to use a flattish cooking utensil with lots of holes
in it for stirring the glaze. I have one in each bucket of glaze and slip.
After stirring I tap this stirring tool on the side and about half the holes
clear. That means it is OK. Most remain blocked means it needs more water.
Most have cleared means leave the lid off awhile for some water to
evaporate.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
This web-site is about to be updated.
Bill Aycock on thu 11 oct 01
I think you misunderstood- my tests worked very well- they just proved that
the instrument was poor for this application. If you are happy with your
use- thats fine. You must use fairly thin glazes with no floculation
tendancies.
If you read my original post- I was satisfied with the use of a hydrometer,
until I was questioned, seriously, by a very good potter. In order to
justify my claims- I made tests. Enough to prove that I was very wrong. I
convinced myself that there were several repeatable methods of getting the
measures I wanted, none of which used flotation.
Sorry about the spelling- I had just had a virus scare, and the company,
'Symantec' (Norton) was much on my mind.
Bill
At 06:44 PM 10/10/01 +1000, you wrote:
>Bill
>I'm sorry your tests did not work. The technique works for us in
>our production glazes & is repeatable to a precise degree.
>I am a better potter than I am a linguist
>Des
>
>BTW- semantics doesn't rule here but correct spelling does
>D
>
-
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
w4bsg@arrl.net
Des Howard on thu 11 oct 01
Chris
Our two main production glazes both Cone 12R, require a nil added
alumina content, hence no clay. These glazes are made up & used
thickly so the tendency to settle is much less. We can usually dip
several pieces before a restir is needed. The glazes do settle solidly
over weeks, tho' not as much as say, a frit containing glaze would.
I have added calcium chloride solution to the glaze slop in the past,
but, as I couldn't discern an appreciable difference the trial was
discontinued. No other suspenders are used. The glazed pots have a
very friable surface, which we have learned to accept,
without too much trauma.
The Cone 10R celadon has a 70% local rhyolite content,
there is an appreciable amount of quite plastic kaolinised material
present in the deposit causing the glaze to crawl off the bisque pot
in drying after thick dipping. So, we calcine the rhyolite.
No suspenders. This glaze we have taken to dipping thickly then
spraying on an extra layer. Next trial for this glaze is to dip
thickly, re-bisque & then another thick dipped layer.
The Cone 10 temmoku has a high uncalcined rhyolite content,
no clay & is dipped thinner, no drying crawling. The Cone 12 temmoku
has a plastic clay content, & is dipped thinner, no drying crawling.
The shino glazes have a 14% clay addition, again thinner glaze layer,
one does have PVA glue added to it , but as a frothing agent,
not as a suspender.
Our other current glazes, copper reds/purples, have
around a 5% clay content, medium-thick glaze layer.
Glaze dip times remain the same, slop weights vary.
Des
Christena Schafale wrote:
> I wonder if the explanation might lie in the fact that Des' glazes have, as
> he reports, little or no clay in them. My experience suggests that the
> "gelled" quality of high-clay glazes (or glazes with the late unlamented
> GB) is partly responsible for faulty hydrometer readings. What do you think?
>
> By the way, Des, why do you eliminate the plastic materials from your
> glazes? And do you use something to keep them suspended without clay?
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
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