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Firepolishing to clear

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Firepolishing to clear

Postby k.russell.glass » Tue Mar 08, 2016 10:39 am

I've got a large piece to grind and fire polish. It is 2 sheets of colour on top of 3mm Tekta, but I am using the shelf side as the face because the detail is more crisp. BUT I have texture from the kiln shelf to deal with. So I plan to either use loose 600 grit and a small piece of glass to grind the full surface OR use my wet angle grinder with velcro pads - 200, then 400 grit on the full surface until I lose the pitting.
Then fire polish. All the fire polishing I've done in the past has just been to 1225F so I can slump at the same time, resulting in a nice matte finish.
But for this work I want as crystal clear surface as I can get, and it will remain flat. So... what temperature should I fire to, and do you have advice about what level of grinding I can get away with?
Thanks
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Re: Firepolishing to clear

Postby Twin Vision Glass » Tue Mar 08, 2016 7:28 pm

Hi Katherine,
I feel you should get as much of the particulates off as you can . So take it down so that you do not feel anything by touch or by eyeing it. Then just bring to a matt finish and I personally would take it to 1375 but that is just me. Put on clean kiln shelf, and put dams back in too with clean kiln wash on them. Go up 50 or 75 degrees per hour so you do not thermal shock.
I look forward to others chiming in and giving advice as well. What do others think.
Leslie Rowe-Israelson
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Re: Firepolishing to clear

Postby k.russell.glass » Tue Mar 15, 2016 7:13 am

So I ground the surface with 200, then 400, velcro pads on the wet angle grinder. This exposed a few bubbles, but I left no other marks on the surface.

I fired it:
75 F/hr - 1225F - 0 min hold
400 - 1350 - 30
AFAP - 900 - 60
100 - 700 - 1
200 - 70 - 0

The surface came out perfectly clear (!) but the bubbles that had opened up did not heal. And I lost my nice crisp beveled edges. So next time I would soak for 10 mins at top temp instead of 30, and perhaps fill the exposed bubbles with clear powder.
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Re: Firepolishing to clear

Postby Twin Vision Glass » Wed Mar 16, 2016 7:30 am

To fill holes you have to take to full fuse to make the glass flow together almost like healing!!! and frit should go to higher fuse or it will look milky as it also has to flow . So many things to remember. And you only took it to 1350 which it does not begin to melt yet completely as filling holes must make the glass move somewhat. So perhaps wait to the end process to polish edges if you are trying to do a few different fixes at once. :? sad though and sorry for all the trouble you had. But I bet it is still lovely! do we get a photo :)
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Re: Firepolishing to clear

Postby k.russell.glass » Thu Mar 24, 2016 5:11 am

Thanks Les! Okay, I won't add any clear powder at this temp. Waiting on more grinding pads before I can finish, then get it in for the fire polish. I will update when it comes out of the kiln.
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Re: Firepolishing to clear

Postby bill.seismic » Mon Nov 05, 2018 4:50 pm

This is my first post to this forum so I hope I'm doing this correctly. I have fired a tabletop, I'm away from the studio right now but I guess it's about 2 inches thick, 18 inches wide and 40 long. I scratched the surface while cold working (flipped it over on the table top side down and didn't realize some glass shards were on the surface) and would like to see if I could fire polish it back without losing the form of the piece, or the texture of the sides and shelf side. I know the goal is to create a firing schedule that does not thermal shock, and stays at a target temp of 1350 or 1375 just long enough to smooth the surface and not cause devit. I read that some say not to use fiber release papers between glass and forms but I feel that I'll lose texture if I don't, and I may lose the nice rectangular shape it I don't dam. Thoughts on a schedule and methodology appreciated. All except one 3mm layer is Tekta.

Thanks for the help! Bill
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Re: Firepolishing to clear

Postby marykaynitchie » Fri Nov 09, 2018 1:26 pm

You need to dam it, and you will need to bring it up to temperature much more slowly because the mass of glass is now thicker.

Mary Kay
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Re: Firepolishing to clear

Postby bill.seismic » Sat Nov 10, 2018 5:30 am

Thanks Mary Kay! How important is it to grind out the scratches? If I go to 1375 would you think that the scratches will heal? They are deep enough to feel when I run a fingernail across them.

Bill
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Re: Firepolishing to clear

Postby martykremer » Sun Nov 11, 2018 5:04 am

Bill- Consider "goosing" it to the higher 1400s for a quick hit of heat to the surface after a soak at 12-whatever. You've got the heat in the work to avoid shock and you just want the surface to flow, not the whole piece. You will have to dam.
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Re: Firepolishing to clear

Postby bill.seismic » Sun Nov 18, 2018 8:01 pm

Thanks Marty - makes sense!
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