Screen Printing multiple images on to Bullseye Cream Glass (000420-0030).
1) A description of the problem:
My project requires screen printing of 3 different coloured images using Sunshine enamel inks (Green, Poppy and Black) on top of each other. Each colour is fired separately using the following schedule:
This schedule comes from Jody Danner Walker’s book “Printmaking Techniques on Glass”.
The 3 mm glass is fired 3 times (for each colour) but on the second or third firings, a large bubble around 5 to 7 centimetres across and 2 to 3 millimetres high forms in the glass pushing that area up. This either prevents me from printing the last layer or using Bullseye Clear on the top to give it a bright shine.
This also happened to a 34 centimetre diameter plate on the third firing. I turned it upside down and refired it hoping to lose the bubble.
I also leave the inspection hole open during the firing to allow any ink gases to escape.
2) If possible, a digital image of the piece and the kiln is often helpful.
Here is a photo of the piece (approximately 42 centimetres by 30 centimetres). This was the second firing and the bump/bubble is circled.
Here is a photo of the circular piece (bubble on the third firing):
Here are the details of my kiln. It is an Evenheat kiln with the Set-Pro system and its internal dimensions are approximately 49 centimetres wide, 39 centimetres deep and 17 centimetres high. The element is in the top.
3) Style codes (i.e. 1101-30), production dates, and sheet numbers for all of the glasses in the project in question.
Bullseye Cream Glass (000420-0030). I don’t have the production dates but the purchase from the Australian supplier was within the last month (January 2018).
4) Design of the piece (dimensions, arrangement)
Bullseye Cream Glass (000420-0030) – single 3 mm piece approximately 42 centimetres by 30 centimetres
Kiln and firing info:
1) Description of the kiln (type, interior dimensions, controller, etc.). Describe location of elements.
Evenheat kiln with the Set-Pro system and its internal dimensions are approximately 49 centimetres wide, 39 centimetres deep and 17 centimetres high. The element is in the top.
2) Firing cycle for this project (including the annealing portion of the cycle)
Kiln Furniture and supplies:
1) What kind of kiln shelf are you using?
I use the original shelf that came with the kiln, approximately 45 centimetres by 35 centimetres by 2 centimetres thick. The shelf is 5 years old.
2) What are you using for a shelf or mold separator? (Thinfire, fiber paper, shelf primer, etc.)
Using Thinfire paper.
3) Where is it situated in the kiln during firings?
The glass is situated in the centre of the shelf.
4) Describe any additional kiln furniture used (dams, molds) and the separators used.
Posts - one for each corner of the shelf and they on the base of the kiln. These posts are 1½ centimetres high.
Do you have a hunch about what could be done differently to avoid the problem?
I have been very careful to have the shelf clean before applying the Thinfire paper. I have also cleaned the glass before screen printing it.
I have tried a lower firing schedule (700C and 15 minutes shorter) but this affects the surface of the ink. It is a matt finish rather than a shiny finish.
I have asked one of the Australian Bullseye suppliers for their advice. She suggested that it may be the shelf which is 5 years old, or the firing schedule temperature may be too high.
I have never experienced this issue with smaller pieces (approximately 20 centimetres).
Any help would be really appreciated.