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Segment melt of pattern bar blocks hazing?

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Segment melt of pattern bar blocks hazing?

Postby jstahl956 » Sat Jan 06, 2018 9:55 am

Hopefully someone can help with what I'm seeing here in this glass. Im not sure if it is devit or possibly from cutting with the tile saw or wrong schedule. Have only been doing glass work for under a year but doing plenty of projects and experimenting. Sorry for the long post but trying to give all the details.

Anyway here is how this became what you're looking at.

Started out making 4 different flow slabs all at 3/4" thick of various lengths and widths. They all looked good coming out of the kiln and even after cutting up three of the four. So not thinking it is from the flow slab melt. Here is the flow slab schedule I used and have used before for flow slabs of similar thickness.Fahrenheit temps.

300 1225 :45
600 1525 1:30
AFAP 900 3:00
45 800 :01
81 700 :01
AFAP 70 :00

Kiln is an Evenheat Studio 24 with side and top elements.

Cut these pieces up on Dewalt tile saw into 1" wide strips that were 3/4" thick. The blade is the 10" Husqvarna Superlok I bought from HIS Glass. Very good cuts.

After cutting each piece, it was laid in water and then cleaned again at the sink with soap and water and individually dried. Before putting in the mold for the plate melt they were cleaned again with alcohol. I did not sandblast the pieces as I have not had a problem with this on another projects. Did a lot of research and it's about 50/50 out there on whether or not to sandblast.

This particular flow slab and plate in question is from the following BE glass material
0345 "steel jade"
0207 "celadon"
0132 " driftwood grey"

Sorry but did not get a photo of the arrangement of blocks to make this plate but it was laid out in a snowflake pattern. Basically a cross but also rows in between the 90 degree cross at 45 degrees.

The shelf used is mullite with BE kiln wash on 1" kiln posts and the mold I made from Insblock 19 fiberboard that was sanded, cleaned and coated in BE shelf primer (4 coats) with 1/8" fiber paper around border. The mold circle was cut to 10-1/4" so I would end up with a 10 circle. The fiberboard mold was 12" x 12" x 1-1/2".

Schedule for 10" circle plate with 1125 grams of glass to achieve a 3/8" thick plate is as follows.

300 1225 :45
600 1525 1:30
AFAP 900 1:30
100 700 :0
AFAP 95 :0

Overall everything looks pretty good but you can see some slight hazing and lines that look like clear film laid over the glass but just the outlying edges of the clear film. Almost all of these are on (or over top of) the "0132 "driftwood grey" color. It is not noticeable until held under fluorescent lighting.

So my question is after all the details is what caused this? Glass, schedule, tile saw cuts or something different?
My next question is how do I fix this? I am thinking of sandblasting the whole top layer with Alumina Oxide 120 to get get rid of these areas.
Do I then re-fire the whole piece (back in the dammed mold) or after sandblasting it, putting it in the bowl slumper and achieving a fire polish.

I have sandblasted pieces but not done a fire polish finish on any pieces so while I know this won't destroy the piece, trying to go about do the right thing asking question thus saving time trying several other things.

BE site and subscription to videos have been a tremendous help in the learning process.
Attachments
pattern bar plate 2.jpg
pattern bar plate 2.jpg (47.73 KiB) Viewed 4625 times
pattern bar plate.jpg
pattern bar plate.jpg (40.76 KiB) Viewed 4625 times
jstahl956
 
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Re: Segment melt of pattern bar blocks hazing?

Postby jstahl956 » Sat Jan 06, 2018 9:59 am

Here is a picture of the piece overall.
Attachments
Pattern bar plate 3.jpg
Pattern bar plate 3.jpg (105.95 KiB) Viewed 4624 times
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Re: Segment melt of pattern bar blocks hazing?

Postby marykaynitchie » Wed Jan 10, 2018 9:58 am

Wow, nice work! I think that the unglossy surface on the driftwood gray is devit. Sandblasting should do the trick, or you can sift clear powder over the whole disc and fire it flat with a shorter time at process temperature (10 minutes is what we would aim for in melting powder onto the surface of an even 6 mm tile of glass.)

The driftwood gray might be less forgiving of off-gassing from fiber paper, compared to the other styles. Just a theory.

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

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bit.ly/BEVID
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Re: Segment melt of pattern bar blocks hazing?

Postby jstahl956 » Thu Jan 11, 2018 9:36 am

Thank you for the feedback. I'll try sandblasting and re-fire it. Planning on slumping into the 12" 8732-mold.
jstahl956
 
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Re: Segment melt of pattern bar blocks hazing?

Postby jstahl956 » Wed Jan 17, 2018 7:45 pm

Segment bowl 3.jpg
Segment bowl 3.jpg (10.09 KiB) Viewed 4471 times
Segment bowl 2.jpg
Segment bowl 2.jpg (39.2 KiB) Viewed 4471 times


Sandblasted the piece with 220 AO and re-fired. Did not add clear powder after SB. All the hazing went away and the only film part I noticed was at the center cross in the Driftwood grey and it was minimal.

Slumped into the 8732 mold and it turned out pretty good. There was a small amount of pulling of what look like stretch marks on the outer part of the bowl. I didn't get the slump schedule anywhere special and used one I thought would work relying on my limited experience. Maybe that was the problem, LOL.
Anyway, it turned out acceptable and will keep it.

Slump schedule I used was
400F 1225F 20min
AFAP 900F 1:30min
150F 700F :0

Thanks again for all the help.
jstahl956
 
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Re: Segment melt of pattern bar blocks hazing?

Postby marykaynitchie » Thu Jan 18, 2018 9:35 am

Thanks so much for taking the time to document your process and share the results! Looking good!

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

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