Crucible cast - Take 2

After isolating a temperature and aperture through testing, the actual project firings have begun.  The goal is to create a slab of glass that can be used for a future sculpture collaboration project as well as a large flat disc that can be formed into some type of lighting piece.

The kiln that I'm using for this project is a side fire Skutt, so I'm going to do two crucible melts at the same time, stacked with shelves.  The bottom of the kiln is lower in temperature than the top, so I'll load the thin disc on the bottom and the thicker slab on the top. 

Here is the large saucer kilnwashed and loaded with supports and a pot of glass.  The center of the glass is large chunk tempered, the blue frit is trickled in around the edge.

 

After firing:

And the final product:

 

The top shelf will be loaded with the slab set up.  I was trying for streaks of blue through a clear base, so I used a square pot with the side broken out and loaded the clear glass in the center with turquoise frit down both sides.

 

  

After firing:

 

The final result:

 

Conclusion:

The slab is successful and can be taken to the next step of the process.  The glass for the blue disc had some impurities in it that I missed, which came back to haunt me.  Some of the disc can probably be used, but a new round of firings are in order, perhaps with different colors. 

Recycled Glass Pot Melt Tests

One of the things about recycled glass that everyone who uses it knows is, you have to test everything.   Twice.  And then do it all over again, since your results could have been a fluke and the worst time to realize that is after you've spent a very long time on something.

So.  In preparation for some cast sculptural work that's coming up, I decided to do some potmelt (crucible) casting tests.  The factors I need to isolate are:  glass particle size, aperature size and temperature.

The most obvious way seemed to test three aperature sizes and three glass sizes at the same temperature.  This would allow me to isolate one factor at a time.

The glass I used was:  ground clear window glass larger than 16# and smaller than 1/8", ground clear window larger than 1/8", smaller than 1/4" and large chunk tempered glass.  All three were mixed with one third by weight of ground Bombay Sapphire bottle glass.

Next I used 9 terra cotta pots, all of the same size, drilled 1/2" holes in the bottom of three, 3/4" holes in the bottom of three and 1" holes in the bottom of three.  Next step; loaded one of each size with one of each glass mixture.

I set them all up in my side-fire kiln (a.k.a. the EZ bake).  Based of past experience, I knew that 1700 wasn't hot enough.  I decided to try 1850 for 15 minutes.

 

Here are the pots post firing (the bottom shelf, the remainder were on another shelf).  With the exception of that center pot, it looks like we got pretty good drainage of the crucibles.  The center pot:

This pot contained the smallest particle size (16# mesh) and the smallest aperature (1/2").  This is very useful, because it gives me a baseline for the bottom end of the success spectrum.

The next step is to look at the resulting melts and see which other combination would suit our purposes the best.

 

This is the smallest particle size (16#) through the 3/4" aperature.  The result is shiny and smooth, but not translucent.

Med size (>16# <1/8") clear through the 3/4" aperature.   The results are very shiny, with some translucency.

Large chunk (~1/2") tempered glass through the 3/4" aperature.  Very translucent and shiny.  

So, the conclusion here is that we need to use about a 3/4" aperature or larger.  Any of the glass particle sizes will work with that aperature, but each gives a very different result.  Next step in the casting process is mold making and further temperature refinement based on increased quantity of glass.