Steve Slatin on thu 18 aug 05
Any interested readers --
Possibly the most important thing I learned from the
previous round of tests is that it isn't necessarily a
good idea to mix rutile wash at 50/50 with 3134 for
cone 6. All of the tests -- Ti-only, RIO only, and
milled rutile were better (to my eye) at lower
concentrations.
My test for last week was using 3134 and Ti at a 2/1
ratio, which put it in the range where the Ti shows
physical migration similar to that with rutile washes,
but without the formation of the highly reflective
crystals within the glaze.
Again, I put it over the clear liner glaze on Seattle
Pottery's 'Sea Mix-5.' I marked increasing
concentrations of RIO; with the following results (RIO
concentrations identified as % of Ti in wash):
1/2% opaque, flat, sort of a winter-butter color, a
few dark flecks visible with magnifier, surface very
smooth
1% similar color, more flecks visible with magnifier
1 1/2% color somewhat darker, some flecks clearly
visible without magnifier
2% many very dark, large patches, visibly darker
overall, can feel surface irregularities (possibly not
mixed as well as it should have been)
2 1/2% Base color now like a mailing envelope, lots of
darker flecks, but smaller than the 2% area, a few
small areas seem to have micro-crystals, but they are
concentrated together into matte 'lands' often with a
dark brown speck at the center, but cannot feel
surface irregularities as well as previous test
3% Very much like previous, but more specks
3 1/2% base color now visibly darker than a mailing
envelope; some areas starting to show marked
crystallization, but it remains concentrated with
ultra-small crystals, again can feel irregularities in
surface
4% base now taking a decidedly orangey tinge, in a few
areas the Ti-influenced migration takes on a bit of
gold color, but there are no sparkly crystals like
rutile gives in the wash, tactile effect as previous
Well, that was last week. The joy of a small kiln is
you get to fire it a lot ...
I used a different shape tile, otherwise everything
was the same, and continued with --
5% Under magnification, the tan/gold areas appear to
be coagulating, the texture can be readily felt. The
white which I attribute to the Ti runs farther down
the new tiles than the tan/gold, which I attribute to
the RIO
6% The tan/gold is nearly solid, but even the unaided
eye can see voids. With magnification, at the 'line'
where the tan/gold ends you can see very small bits of
it 'riding' the white down. (I suspect gravity in the
melted stage.)
7% As the previous test, but the color of the matte
area is turning quite brown.
8% A sort of over-cooked toast color overall, the
texture of the matte area is markedly abrasive, even
the unaided eye can clearly see the tan/gold color
appear lower down where the RIO effect ends and the Ti
effect appears alone.
Even the darkest areas in the test above are not as
dark as the clearly brown areas in a true rutile wash.
My next round of tests I will either try adding a bit
of zirconium (or possibly alumina) to see if it
changes things, or perhaps try to 'seed' the mix with
something crystalline and very regular in structure
that melts high enough so it'll remain solid in the
mix. Not ulexite, that melts too low, maybe some
finely-ground hematite or ilmenite ... ilmenite would
change the chemical composition less, but hematite
could possibly substitute for some of the RIO ...
something to think of as I drop off to sleep.
Several other folks have told me they are
experimenting as well. I look forward to more input.
-- Steve S
Steve Slatin --
Drove downtown in the rain
9:30 on a Tuesday night
Just to check out the
Late night record shop
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