At My Wits End - Part Two

[Randy W]

Well, I gave it another go and tried a couple of new things.
This time I put talc on a properly prepared and dried shelf. I laid two strips of single strength ( 3/32" ) on the shelf and ran a straight edge across them to level the talc and make it an even thickness. Then I placed a 14" circle of clear 96 COE glass on top of the talc. Then I set up my pot melt and fired away. I went AFAP to 1675°. I peeked at 1400° and my base piece had broken into about 15 pieces cause of thermal shock. D'OH!
I should have known better, just wasn't thinking. I let it cool and tried the next day.
The next morning I picked up the pieces, vacuumed up the powder and started over. Got it all set up again and this time only heated up at 500° per hour. The base piece didn't break this time. I checked it at about 1550° and there were a number of one inch bubbles in the base piece. The pot was already flowing so I just let it go. I new it wasn't going to turn out right but figured I could still learn something.
I took the piece out this morning and here's what I have.

http://f1.pg.photos.yahoo.com/ph/74dodg ... /my_photos

The talc came off the back of the piece with just a brush on the end of the shop vac. But there is a thin layer of talc that did fuse right to the glass. After I cleaned it off I could see where the bubbles were. All 22 of them. And where ever a bubble came through to the surface, it brought some talc with it. ( see pictures 3 and 4 )
The back of the piece has a number of veins running across it. (pictures 6 and 7 ) An interesting effect but not what I wanted. The talc also turned brown, is that normal ?
I changed my firing schedule and annealed slower.
500° per hour to 1675°, hold 2 hours.
AFAP to 1100°, hold 1 hour.
60° her hour to 600 °, off.
I over annealed on purpose just to make sure I covered all the ranges.

I'll wait a few days to see if any cracks appear. Then I'll sandblast and see what happens. I'm using worn out 80 grit garnett at 55 PSI.

Randy

[Tom White]

Randy, was your talc raw pottery talc (gray in color) or had it been fired (calcined) as hot as you anticipated firing your pot melt? When using mica flake inclusions between layers of glass I got excessive bubbles until I calcined the mica to 1900F in a cone 05 greenware firing with a load of low fire earthenware ceramics. After that it fired with minimal bubbles. My work with potmelts has been with 30 gram loads in a 6 x 6 x 6 quickfire tabletop kiln for producing jewelry cab pieces. I use half a christmas ornament or half an easter egg with a 3/8" hole in the bottom supported on an inverted cup with a hole in the bottom to support my mini pot about 2" above the shelf. My best release has been 15% EPK kaolin, 85% finely ground alumina hydride @ 100 grams in a pint container with 4 fl oz of a 10 grams of CMC gum per pint of water solution as part of the liquid to provide green strength before firing. I use an airbrush to apply 4 to 6 thin coats to my shelf. I fire pot melts onto this shelf surface with minimal sticking to the glass. I fire until no more glass will drip from the pot. After rinsing and scrubbing with a red Scotchbrite pad I use a Dremel 120 grit flap sander on the back surface to remove the very light coating of kilnwash which sticks to the glass at that temp and leaves the surface feeling slightly gritty. I showed some of these to Sara Creekmore when she and David were in Houston for the Quilt Show. When I have squirted a heavy layer of this kilnwash directly onto the shelf I have observed some wrinkling or veining on the back of the glass where the honey consistancy glass moved the extra thick layer of kilnwash while the glass was soft. I wil try to scan and post some of my small potmelts in a day or so.

Best wishes,
Tom in Texas

[Candy Kahn]

I loved the title of your picture album "Stupid Pot Melts" - made me laugh and I love a good laugh.

candy