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updated sat 20 mar 04


Susan Setley on wed 17 mar 04


In a message dated 3/17/04 4:16:12 PM, djhoward@HWY.COM.AU writes:

> Craig
> The whole point is that it does not have to be universally true
> & reproducible in anothers lab.
> This is the viewpoint of the scientist, I take the viewpoint of the
> engineer,
> can I get it to do the same thing, here, tomorrow, next week.
> When direct experience flies in the face of authority at any level I give
> authority the flick.
> Des

I think the argument that because a hydrometer is not a tool all people can
use in all circumstances, it has no use, is not valid.

It seems to work very well for my work to develop good terra sig. I think it
was Vince who suggested I get one, and it was a good suggestion.

If it does not measure everything perfectly, then I'll use something else. In
the studio where I work (and do all of my glazing) we have not needed any
measurements for the glazes. We were just taught what the glaze is supposed to be
like. Some do better a little thinner; a few do better a little thicker. They
all have to be thinned a little for the sprayer, but we do that in such small
amounts that there wouldn't be any way to measure it anyway.

I think for those producing glazes commercially, they should know exactly
what they have. But there are multiple ways to judge for others. My only
experience with a hydrometer is for terra sig, and for that purpose -- I like it.

Susan Setley on thu 18 mar 04


In a message dated 3/18/04 10:40:02 AM, Taylor_Hendrix@BAYLOR.EDU writes:

> Carol:
> You are right.=A0 It matters not a whit what you use for the measurement
> as long as you can reproduce it the same way every time.=A0 You could make
> your own ceramic container for glaze slip weighing too.=A0 It doesn't
> matter if it's really a pint or not.=A0 The problem would only be those
> numbers are not portable.=A0 You couldn't make suggestions to someone
> trying to reproduce your results for example.=A0 This is not an issue for
> many.=A0 Of course one of the benefits of standardized measurements is
> that an inch is an inch is an inch is about 2.5 centimeters.
> I say use what works for you.=A0 Heck use a fish float if you don't want
> to buy a hydrometer and you fish.=A0 Be warned thought that when your dog
> chews up the float, you will have to do all your numbers over again.
> Sigh.
> Taylor, in Waco

That's how it's working for me. I made a ceramic column, and I use the=20
hydrometer to measure the density of terra sig, the only surface mixture I m=
ake at=20
home. It has run very true... Vince said the minimum density for terra sig i=
1.15. My first batch was 1.05. I had a known 'good' commercial batch. I coul=
not see any difference using a 'dip the finger' test, but the commercial sta=
where you put it, and mine was runny.

I eventually evaporated it down to 1.1 -- and it was still too runny. That's=
probably all I'll ever use it for, but given the amount of work that goes in=
a piece with a terra sig surface -- it was well worth the $15.

Susan Setley on fri 19 mar 04


In a message dated 3/19/04 10:10:39 AM, craigedwards@CHARTER.NET writes:

> Hello Ivor: I agree with you that accuracy and precision are goals when
> using measuring tools. The main point that has been brought up for using
> a hydrometer instead of a graduated cylinder is not accuracy and
> precision however but convienence and quickness. It's one of those good
> enough types of things.
> It seems that 20 seconds is what is wanted for an acceptable time, using
> a graduated cylinder it takes me about a minute--I get an accurate
> reading. Far to long a time to be acceptable.

That's a completely unfair putdown. Some of us didn't even KNOW there was
another way, and believe it or not, what has been described here as a substitute
won't even work with everyone -- for instance, because they work with small
amounts, as I do.

We made a very interesting discovery based on my "good enough" (not lazy)
approach: while my terra sig is thin, when pieces were accidentally bisqued too
high, the commercial terra sig peeled off but mine did not. We think mine is
thin not because there was too much water but because the particles may be
extremely fine. It may have been a happy accident, and if that is true, I would
rather have more information about it. But since I only make about 1/2 gallon at
a time, methods that require floating jars in buckets won't work, while a long
piece of weighted glass in a tall cylinder will.

It's not laziness, and it's not impatience. Honestly, must we all be so

I'm sorry Snail, but "anyone who doesn't do it my way is lazy" is not a fair

Susan Setley on fri 19 mar 04


In a message dated 3/19/04 10:14:28 AM, rolybeevor@CHRISTISON.COM writes:

> A digital thermometer may give a rather unreliable (several percent off a
> true reading) and unreproducible (another thermometer will give a differen=
> temperature) reading of temperature in a kiln, but it has good
> discrimination so it can tell you whether the kiln is getting hotter or ha=
> stalled, precise but inaccurate in your terms.=A0

Exactly. Sometimes they stall out. Even if the thermometer doesn't give you=20
the temp to the exact degree, it will still tell you the kiln isn't climbing=