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making hydrometers

updated fri 3 jan 03


Carol Tripp on tue 31 dec 02

I've got the Aussie directions for making an hydrometer. Thanks Roger and
Des. Local straws are too skinny so I stole one out of a drinks canister
and stuffed slingshot shot into it but it sank to the bottom of the bucket.
This is a heavy straw. I cut two of the shots off. By this time, the straw
didn't look like the instructions so I was going to pack it in when I
remembered Brad Sondahl has directions too!
So I have used his making method and the Aussie straw idea and now I can
measure glaze thickness with more than just my finger.
Ah, Clayart. What one can learn.
Best wishes for the New Year.
Dubai, UAE

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Roger Graham on thu 2 jan 03

Further to Carol's post from Dubai, re construction of a home-made
hydrometer. If you want to use the calibration chart offered with the
"Australian" version from Des Howard's website, the hydrometer must be a
simple straight-sided cylindrical shape (like a drinking straw, or a wooden
dowel if need be). Any extra weights added must be inside, not bumpy bits
sticking out from the bottom, like sinkers or steel screws etc.

Not that the hydrometer will work any better, one way or the other. Just
that the calibration chart was made up for a straight cylindrical shape, or
at least for a shape which has constant cross-section area all the way down.
No bumps. No fat bits.. The actual specific gravity figures from the chart
won't be accurate otherwise.

The original version was built around a McDonald's straw, but there's
nothing special about these (except that they're common, and robust). A
thinner straw works just as well, of course, but you'd need less weight in
the bottom. Just fiddle with the amount of lead until the straw sinks a bit
over half way in plain water. Everything else is the same

Roger Graham, near Gerringong, Australia