Vitrograph Cane

[Warren Weiss]

Yesterday I pulled cane from my vitrograph kiln for the first time. About the last 50 % came out hollow. I used a 6" d x 4 1/2" high clay pot with the hole reamed to 1/2". I used my Paragon kiln controller to set the temp. at 1650 F. The pot was filled with a stack of about 2" squares of glass using 2 layers of clear and 7 squares of each of 4 colors separated with clear. The stack reached the top of the pot. The kiln lid was raised about 2" with fiber blanket for clearance. As the glass melted it must have spread out to the edges of the pot. I guess at some point the hole must have not had glass over it and fed from the sides forming a hollow tube. Does anyone have suggestions on how to avoid 50% glass "straws?"
Thanks.
Warren

[Morganica]

How are you stacking?

[Warren Weiss]

Hi,
Stacking straight up. As the pot diameter increases toward the top, there is much more side space near the top. The squares are uniform in size.
Thanx,
Warren

[Haydo]

Not sure when I started doing this, but I lay one piece of dense white at the bottom of the pot to cover the hole and then proceed to jam pack the pot with glass right down to waste fragments to fill the gaps. My thinking is that maybe the white being a stiffer glass will support the mass of glass above while it melds, it's also at the coldest part in the pot. When I'm ready I prompt it to move by using a torch and pointy nose pliers. I normally only get the tubular glass toward the very end of pour when the pot has a fifth left, depending on size of aperature. All big pieces of glass that goes into my pots are vertical. With bigger holes in the pot alot of the tubes can be kept for other work.
peace, haydo

[Valerie Adams]

I only get straws at the end of a pull. For murrine, I load my pot with circles that are loaded flat into the pot, adjusting the size to fit the shape of the pot. For cane, I load the pot with 1" square homemade billet chunks that I've pre-fired from sheet glass.

My top temp is about 1525°, ramped at 300° per hour.

[Warren Weiss]

Thanks. I think the "trick" is making the circles larger to match the slope of the pot. It might work if I stack uniform size squares and then place 4 stainless steel plates to "box in" the squares. That would cut the capacity of the pot, but would keep the color sequences and desired change overs consistent.
Warren

[Morganica]

uhm...

[Morganica]

The trick seems to be leaving as little airspace as possible in the pot, so that it's essentially a solid chunk of glass. I took a glass in vitrograph stringer years ago, and we just piled in scrap glass, willy-nilly. We got a tiny hollow in the stringer almost immediately. The tighter the pack, the longer it took the hollow to appear.

I took Nathan's vitrograph cane class last year, and noticed right away that, like Val, he packs the glass into the pot as tightly as possible. If you start by packing the cubes around the edges and cut to fit, you'll get it tighter. Or you can look for a straight-walled container.

Actually, I love the straws if the walls aren't too thin (I dumpster-dove at the end of Nathan's class to grab all the straws the rest of the class was discarding). You must be a little more careful with them--you can't use murrini choppers, you need to saw them apart--but you can set them up like murrini in a flat blank and fill the holes with frit, stringer, rod, etc., to get different effects. Or you can use the thicker-walled straws as beads in jewelry; just grind and polish the ends and you essentially have furnace glass beads.

[Cheryl]

if you use the hollow cane, you will get air bubbles and the cane looks irregular - straight then blobby, straight then blobby. I agree with Cyn; the tighter I pack my pot, the less hollow stringer I get. I get hollow stuff only at the very end.

[Warren Weiss]

Thanks Cynthia and Cheryl. That is what I suspected was happening. The more I think about it, the more I like the idea of boxing in the squares with stainless steel. There will be no air in the pack and colors and change overs will be in register. Also, squares are a lot faster to cut than circles and a lot denser than scrap packing.
Warren