I.Lewis on thu 7 oct 99
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This has been an interesting strand and I have followed the scientific =
arguments
wondering what they are all about.
Some years ago I made a large batch of salt glazed Port Wine bottles =
complete
with wooden spigots. One came back with the complaint that it was weeping a =
very
fine sweet heavy Madeira. Now I know that South Australian wines, classed as
some of the best in the World, give wood spigots a hard time because of =
acidity
and I have always exchanged these immediately without a quibble.
Seepage was a new experience. Yes the pot was weeping a costly sweet sticky
exudation. I exchanged it. Filled the offender with water and sure enough, =
it
started to weep. So did the replacement. Gave the money back and did a swift
recall. No further problems.
Well, I=92ve been thinking about the oil lamp problem and read all the =
advice and
arguments. Sorry, I find the notions about molecule size and shape a bit
unconvincing. I find it difficult to comprehend how oil can get through the
fissures better than water does. I am unconvinced.
So I Put the Fish in the Water, so to speak.
Experiment. Cut two pieces of fine capillary tubing from the same length of
glass. Stuck ends in a light oil, peanut to be exact, and into rain water.
Observation. Water rose twice as far as the oil did up the same sized bore =
of
tubing. Substituted Kerosene. Same result except the kero did not rise as =
far as
the peanut oil.
Now, I am observing Capillarity in action. Capillary action is the result of
association of two forces, Surface Tension and Cohesion, simply put, pulling=
and
hanging on. Doing it against a vitreous material. So what price the theories
which have been aired. Aided by Gravity, these forces make the liquid flow
through confined spaces. They make the fuel flow up the wick as well=21
My solution to the problem. Simple and well known. If it is suspected that =
there
is the slightest chance that your glaze may at some time craze and =
recognising
that most stoneware clays may have some inter-communicating porosity, pour a
solution of sodium silicate into the pot and allow it to soak in well for a =
few
days. Let it to dry then test it for seepage. The problem should be cured. =
The
port bottle problem was solved with greater efficiency. Just stopped making
them, recognising that Salt and Soda glazes are high linear coefficient
materials and are prone to crazing. Also the clay merchant told me that the =
clay
would only fire to ninety eight percent density.
Sorry if that seems long winded, my style of thinking and writing.
All the best with the lamps.
Ivor Lewis.
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