Firing

Here is our firing schedule for our kiln-pressed glass:

Segment Ramp Target Hold
1 300° F / hr 1225° F 3 hours
2 FULL 1500° F 1.5 hours
3 FULL 900° F 2 hours
4 100° F / hr 700° F none

 

The long hold at 1225° F allows the glass to compress, eliminating much of the trapped air and helping the shelf to stay level as it drops.

The long (90 minute) fuse ensures that the glass is fully pressed so that the shelf rests on the fiber spacers.

Our annealing (from 900° F to 700° F) is fairly aggressive – that’s because our glass is exceptionally thin so there is little reason to be worried about heat differentials.

After 700° F, we can let the kiln cool naturally.  Thanks to all the extra mass provided by the weights, cooling will be very slow.  You can vent the kiln at 500° F and open it fully at 300° F without worrying about thermal shocking the glass (again – because it is so thin).  At 200° F, remove all the weights and shelf to allow the piece to finish cooling.  Be careful when taking out the weights – they will often be hotter than the ambient temperature of the kiln.

With the weights and top shelf removed, you should see something like this:

Kiln Pressed Glass

Congratulations!  You’ve completed your first kiln-pressed glass!

We aren’t stopping there, though.  Read on to see how we can continue to improve our project.