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
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!
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!
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.
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
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
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
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
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.
Quote from: Penglass on January 28, 2014, 08:20:56 AM
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?
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!!
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
let us know how you get on.