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.

 

annealing question

This is an interesting technique with beautiful results.  I am confused about the annealing.  What kind of glass are you using?  You say you are annealing between 900 and 700 degrees. I thought I understood shotgun annealing, and that the glass molecules lined up at a higher temp.  Could you clarify this for me please.

cecilia

annealing

Cecilia

The major annealing takes place during the 2 hours at 900 F, which is actually a pretty long time for a thin piece of glass.  The slow cool down between 900 & 700 F gets the piece safely past the strain point, about 850 F for Bullseye.

Piranga

Fused Glass, Wood, Beads, PMC, Ceramics

Usable and Wearable Art

Art for the Sake of Art

1st attempt-1st firing

Thanks for this tutorial. I've just completed the first firing with good results that could use refining so I'd appreciate feedback.  For those interested I am posting a photo in the gallery.  I started with a 6" diameter irid on clear base and stacked 3 more layers: color, clear, color.  I then filled the open areas with clear and followed the firing guide precisely with one exception:  I annealed at 950F per System 96 guidelines.  I used thinfire under and over (the kiln shelves were also primed) and had only one small spot of stickage. The fiber paper spacers I used measured about 5mm thick using calipers-enough for the top shelf to float above prior to firing.  The resulting disk was 8" and fairly symmetrical (what I expected thanks to the Pot Drop Calculator).  The first issue is my bad: using irid as the base.  I did it because I had a small piece available, it helps keep kiln wash and paper from sticking and it's pretty.  Of course the irid coating did not spread (it's an admittedly "duh" moment) so the 2" spread has no irid.  But I need help with the other two issues: 1)  the darker colors didn't spread as much as I'd like.  Would placing another layer of clear on top of the colored glass aid in this?  And, 2) the outlines of the clear filler glass are visible.  This may not be evident in the photo but is unsightly and I'm puzzled given the high temperatures and long hold times.  My plan was to add some reds and yellow in the 2nd firing and I may still do this. I certainly hope to hear back with suggestions.

 

breaking Shelf during prosses

This is my second attampt at this and both time I lost my bottom shelf to breakege from the pressure.

What am I doing worng I follwed the instruction to the T.

I never did get any answers I would stil like to know what i did worng

Both time my Glass press came out great but I broke my shelf and that is way to costly for me for creative art for seling.

This particular photo.

I don't understand the photo. Obviously around the perimeter glass has been pressed out. What are the three dark pieces in the middle? Like I said, I don't understand what I am looking at...why would the whole piece not look like pressed glass?

1st attempt post

Did you ever get a response to your questions? It was your picture I was asking questions about. I can see the edges of the different glasses, and would not like that either. You did explain about the three dark ones in the center, though. If there was an answer to this, is it private? I don't get it, why invite posts and not reply? I am missing something, right?

breaking Shelf during prosses

I am not the one who sent the picture, I believe there is a mix up in the link.

1st attempt post

Lindajo92:

If I understand your concerns and they were intended for my questions regarding ghost lines of glass pieces then yes, I did get an answer from Paul.  I had also posted in a separate area which is where his answer appeared.  I believe it is the first page of this tutorial.  He suggested a fire polish which worked on my second attempt.  I've removed the pictures of the first attempt from my gallery and replaced with the latest, successful piece.  Hope this helps and happy firings!

 

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