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Part Sheet plate problems

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Part Sheet plate problems

Postby jstahl956 » Wed May 09, 2018 6:24 pm

Started out making River Rock part sheet (PS). It turned out good. Made another part sheet using tekta with 2mm stringers in following colors: 0100, 0116, 0126 & 0009. Those came out good too.

Plate project.
Firing schedule used for making plates from part sheet pieces
400F 1225F 1:30
600 1490F :10
AFAP 900F 1:00
150F 700F :0

Fired plates to schedule above and had issues with all three. Hazing or cloudy through all the part sheets.

Have watched the 3 different subscription videos on making part sheets and plates. Also have watched video an understand the bubble squeeze.

The one video states that part sheets are prone to devit on the side that rests against the shelf. I sandblasted the shelf side with 220 AO sand, scrubbed and cleaned with both soap and water then alcohol like we do everything that I sandblast. Here is where where maybe the issue lies. The bumpy side or non shelf side was faced down and the shelf side (having been sandblasted) was placed face up between the capped Tekta.

Glass used for plates.
#1: 1164 border around river rock PS. Capped w/ 1100 Tekta. 8" x 8"
#2: 0100, 0321 around river rock PS. Capped w/ 1100 Tekta 10" x 10"
#3: 0100, 0104 around PS made with stringers. Capped w/ 1100 Tekta 16" x 4-1/2"

#1 Cloudy window through all part sheet. Champagne bubbles on border. This one is really not bad other than one bubble that is a little large. The cloudy part sheet looks pretty good with the blue transparent border.
#2 Had some clear window thru PS but majority was cloudy. Splotchy.
#3 Stringer PS is very cloudy and there are bubbles that almost appear to have small cracks radiating out from them. Majority of the larger bubbles are on top of the black 0100 stringer. Not sure why that is?

I thought the bubble squeeze at 1225 for 1:30 would have been enough but evidently not. Maybe on plate this big should shoot for 2 hours. As for the hazy areas, maybe I shouldn't have sandblasted them and had that part capped with Tekta?

Part sheet plates pre fire RS.jpg
Pre fire
Part sheet plates pre fire RS.jpg (17.95 KiB) Viewed 2827 times

Part sheet plate RR Blk pmk2.jpg
Part sheet plate RR Blk pmk2.jpg (22.76 KiB) Viewed 2827 times

Any help our suggestions would be greatly appreciated. Not sure if they are repairable at this point.
Part sheet plate stringer RS.jpg
Part sheet plate stringer RS.jpg (19.6 KiB) Viewed 2827 times
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Re: Part Sheet plate problems

Postby marykaynitchie » Fri May 11, 2018 8:38 am

I think your theory about the cloudiness seems plausible.

Re the stringer part sheet, the positions of the bubbles suggest that the air between the sheets did not have time to escape before the edges softened and sealed. A slower ramp up would help--perhaps 250°F instead of 400°F.

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

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