"Dog-Boning"

While in the interim between the club's Fall Festival and next Monday's X-mas party (where official duties are I basically just attend and say a few words), I have been back working with glass. The pieces needed for me to finish the latest wind chimes for gifts are ready for assembly, one needing some wood finishing for the top support (saguaro rib) and the other with a circular top needing its plan for putting it together.

I had a good supply of glass left in large pieces, along with a request to teach wind chimes to fellow club members. With the newest diamond drill bits performing up to my standards, I was ready to take advantage of the hiatus by finishing cutting and baking pieces of glass to finish off the supply. 

Or so I thought. But the person asking me to take over the class she'd been teaching also donated a huge amount of large glass pieces to the club to work with for the classes. The original reason wind chimes had been developed as a class was a way to get rid of quantities of donated glass. The club had been doing glass fusion in small pieces for jewelry so far, but for that you MUST know the COE of the glass, aka coefficient of expansion. Glass expands and contracts during heating and cooling. It is after all, a liquid, just a mostly very slow moving one. It's long been noted that 100-year-old houses with equally old windows in them have glass that's thinner at the top, fatter at the bottom. It flows. Downhill. Wherever that piece of glass on a flat horizontal surface thinks that is.

We speed that process along at kiln temperatures. The glass goes into the kilns with cut edges, sometimes ground ones with the right equipment. But in the kilns, glass has a mind of its own as to where it is going to flow while it melts,  expands, and contracts. It flows, sometimes more, sometimes less. Sometimes comically, cartoonishly. A straight cut piece can curve into a crescent. Another piece won't move at all, won't get a top gloss, just sits and hardens, keeping any jagged bit that was left unless ground down later.

With all those different reactions, the second rule of glass fusion is to NEVER EVER mix pieces with different COEs. (The first is everything you need to learn about safety.) If you put a 90 on top of a 96 and hope they fuse together, most likely they will shatter upon touch once cooled. Or a 96 on top of a 90. It's not guaranteed, but very likely, so why waste time, glass, and the energy to run a liln to risk it?

Donated glass almost never comes into the club with any COE notations. We buy ours from a manufacturer's catalog to be sure, and mark it immediately before setting it out for sale. We can't combine unknown with unknown, so have to find uses for single pieces of it. Wind chimes are great for the task. We might also do slumping, where a large piece of glass sits on top of a coated, hollowed out ceramic form and slumps down into it, making a candy dish, candle holder, or whatever else the form was designed for. 

But even with flat cut single pieces, you get whatever the glass gives. Sometimes it's "dog-boning", forming whole new shapes. A long rectangle might contract in the middle and expand on the ends, like a dog bone. Hence the name.

The blue piece in this photo is a very mild version of this, barely enough to notice. The purple and cream again is very mild in reshaping itself, but also shows how, with known matching COEs from purchased glass, one piece laid on another can just sink in smoothly. Note that the "smoothly" part is not guaranteed, sometimes they just stick to each other and maintain height differences. The three green pieces are extreme examples of dog-boning.  The two with narrow necks and wide opposite ends originally were trapezoids, slight difference in width top versus bottom. The bottom left one was cut in a diamond shape. Everything shown had four straight line cuts before coming out of the kiln. You learn to live with a level of chaos. That, or go do something else.