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Author Topic: Hepl. Hazy edges!  (Read 2348 times)
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Penglass
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« on: January 26, 2014, 03:55:15 PM »

Hi I have just bought a 21" x 21" shallow square mould for slumping. I have cleaned my glass meticulously and followed the slumping schedule recommended by Bullseye, however, I am getting a slight hazing along the edges, it's not shiny, more as if someone had smeared something on it or lightly rubbed it with sandpaper. Does anyone know why this is happening and what I can do to prevent it. Thanks
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SilverGems89
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« Reply #1 on: January 26, 2014, 04:21:45 PM »

Sounds like devitrification to me, sorry I don't know what causes or how to avoid, but I am sure some searching will find an answer!
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jeannette
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« Reply #2 on: January 26, 2014, 05:36:42 PM »

It could be devit - did you grind the edge at all - sometimes this leaves a scummy mark as well. I was just researching this...
Here are some descriptions and solutions
http://warmtips.com/20051026.htm
http://glasstips.blogspot.co.uk/2009/08/devitrification.html
http://en.wikipedia.org/wiki/Devitrification

You can do a few things to try and get rid of it.
1 - User an etching fluid, re-fire to fire polish it
2 - Sand blast and do the same
3 - Make up or buy a debit spray and fire to polish it

I literally just had my first experience of this - off to try armour etch on the pieces and fire again.
So, no idea what will work well!
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Jeannette xx

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flame n fuse
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« Reply #3 on: January 26, 2014, 05:38:00 PM »

I agree, it sounds like devitrification. There are extensive and inconclusive discussions about it on the Bullseye Forum on their website - well worth a look.  I find that I get less devit if I use a cooler programme than BE recommend.
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Penglass
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« Reply #4 on: January 27, 2014, 05:30:18 PM »

Would you mind sharing your programme with me? I was wondering about that as the programme that came with the mould is slightly cooler and it says its for Bullseye.
Thanks everyone
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flame n fuse
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« Reply #5 on: January 27, 2014, 10:57:49 PM »

This programme was for a 36 cm diameter dish, with a 3 mm tekta base and a 3 mm layer on top of various colours and frit

To fuse it, the programme was
   Rate    Temp    Soak   Duration   Elapsed
Initial   100   100   10   1.17   1.17
Pre-rapid heat soak   200   677   30   3.39   4.55
Rapid   full   780   10   1.53   6.08
Rapid cool   full   600   10   0.53   6.61
Rapid cool 2   full   516   60   1.17   7.77
Anneal   50   300   0   6.00   12.61
Final cool   full   21   0   1.86   14.47
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flame n fuse
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« Reply #6 on: January 27, 2014, 11:03:49 PM »

sorry, hit send too soon!

then to slump it, .....
          Rate   Temp Soak Duration   Elapsed
Initial   125   250   10   2.17   2.17
Iniital   150   638   10   2.75   4.92
Rapid cool   full   516   60   1.43   6.35
Anneal   50   300   0   4.32   10.67
Final cool   full   21   0   1.86   12.53

sorry, the columns aren't well aligned. If it's not clear, I could PM you. This was done in a top-loading Kilncare kiln, which has elements in the lid.
Hope this helps. Julia
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Penglass
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« Reply #7 on: January 28, 2014, 08:20:56 AM »

Thank you Julia. I have a Paragon 8. I am still quite a Newbie but I thought the annealing temp for Bullseye was 482? What is PM?
Thanks,
Penny
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flame n fuse
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« Reply #8 on: January 28, 2014, 10:52:14 AM »

we played around with a lot of variations to programmes and this was the one which worked for us. You will also see that the maximum temperature which we take it up to in the fuse is a bit lower than recommended - we found this made quite a difference to the final finish of the piece. We now use this programme consistently (since 2009) for a lot of big and complicated dishes and find that it gives us a good finish and have had no problems with it. Hope this helps.
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Zeldazog
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« Reply #9 on: January 28, 2014, 12:53:00 PM »

I am still quite a Newbie but I thought the annealing temp for Bullseye was 482? What is PM?

Bullseye did some research, more to do with thick and/or large cast pieces and found that their glass will anneal at 482, which saves a little bit in production time, but they have stated that it's okay at 517 too.


Penny, did you do a full fuse first, how many layers is your glass, what temperature was that at, did you grind the glass, what schedule did you slump at?
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Zeldazog
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« Reply #10 on: January 28, 2014, 12:55:05 PM »

Oh, and anybody be careful of fire polishing after slumping - it's hotter than slumping temperatures, I tried to save a bit of time once as I needed to fire polish something after a full fuse, and so I risked pushing the slumping program a little - got a wobbly edged dish!!
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Penglass
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« Reply #11 on: January 30, 2014, 10:07:18 AM »

Hi. I fully fused a total of 6mm, didn't grind and fired everything to the schedule suggested by Bullseye. Julia suggested firing at a lower temperature on both firings so I might try that! Thanks
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flame n fuse
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« Reply #12 on: January 30, 2014, 11:51:34 AM »

let us know how you get on.
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