[ATM] Some small successes in glass and ceramic mirrors

[vorblesnak@peak.org]

Craig is a friend of mine down in Coos Bay. He does some basic ceramic
work, has a small electric kiln, and a large interest in ATM and my odd
projects. We talked about my failure with pyrex and ceramic and came up
with a punch list of test ideas he could run in his kiln.

He is working on a tile project right now and has some 05 clay he is
making the tiles out of. For Pyrex he bought a pie pan and tried to break
a circle out of the bottom... That didn't work. Using the shards from the
baking pan he laid out a series of test fires. I have enclosed his latest
missive to me. The pictures he is speaking of can be found at ...

http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Fusing/

It seems a thin coat of glaze is important, though we have not tried some
of the other suggestions received. It is interesting to note that even in
his test the Pyrex did not stick to raw ceramic. Enough of my prattle,
here is his note. David


Here again is the "before" picture --and note that the right hand shard
bears a pair (top and bottom) of my score lines.

Start if Run.jpg


After a run to cone #05 --about 1915 degrees F, my score lines finally
worked and the crack went through, but no where else do we see cracking or
crazing. the Pyrex and this commercial (low temp) tile appear to be well
matched as to COE.

Results 1.jpg


Also, the upper shard appears to have lost half of its shine, while the
bottom shard has lost all of it. This might be due mainly to
"devitrification", an annoying phenomena that occurs if regular glass
tarries for very long between 1100 and 1400 degrees. The temperature of my
nearly empty kiln was dropping off fast, so I gave it another shot at 1175
degrees, so as to pass more slowly through the annealing temperature (1040
degrees F), but that ran it up to 1250 degrees, which is the lower end of
devitrification. I think I should have just let it drop off.

Note also that the curved shard flattened right out and quite melded into
the lower flat shard, even though it retains enough relief to distinguish
between the two.

Results 2.jpg

That lower pair of shards slid right off --no adhesion at all, while the
upper shard is thoroughly welded via the transparent glaze I put on the
tile there. I could not get a knife blade under it anywhere.

The frit Pyrex stuck a little bit --to the underglaze printing there, but
it was no problem to budge it with my pocket knife --and some moved with a
fingernail. The sharp edges are all gone, but there's still unconsolidated
frit --or stuck together in twos and threes. It seems like it leveled less
than the big pieces.


And there you have it.


Craig



_______________________________________________
ATM mailing list http://www.atmlist.net/