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Author Topic: devit  (Read 3035 times)
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jackiesimmonds
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« on: February 15, 2015, 05:50:49 AM »

I have made a number of pieces, some quite large, out of float glass, at the class I attend.  Every one has turned out fine.....fused, then slumped.
I recently collected a handkerchief vase, made from two pieces of float, with silver foil inclusions, and some powders.  It was GHASTLY, totally devitrified all over, really cloudy, and the edges were a horrible dark grey - quite uniform, but looking dirty!
My tutor said I should have painted it with Borax before slumping it.
 I was so stunned that she had never told me this before, and that she went ahead and fired my piece knowing full well that I had not treated it with borax.... I never thought to mention that all of my other pieces had been slumped without this precaution, and they were all fine.
 Stupid me.
It was draped over lots of used fibre blanket, sitting on a form.  I had done one the previous week, no problem, came out crystal clear. Do you think it was just that I had not cleaned the glass well enough.....or that something different was done with the firing schedule (which I have no control over).  I am now panicking, as I have lots of float to use up and am terrified I will ruin everything.

Incidentally..........I did not check it was non-tin to non-tin, but it did come out of the first fuse totally clear, no devit.  The devit only happened at the draping stage.

Any clues gratefully received
« Last Edit: February 15, 2015, 05:53:53 AM by jackiesimmonds » Logged
flame n fuse
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« Reply #1 on: February 15, 2015, 10:21:12 AM »

Can you post a photo? grey edges don't sound like devit
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jackiesimmonds
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« Reply #2 on: February 15, 2015, 11:31:56 AM »

Let's see if I can make the include photo thing work:

[/url]wierd vase by jackiesimmonds1944, on Flickr[/img]

 Undecided      Huh  sure I did this last time...uploaded to Flickr, opened, found the BBcode, resized to small,  copied, opened the image icon here, pasted the code in between. And tried just pasting into the text without hitting the icon, in case that was wrong.  

[/url]wierd vase by jackiesimmonds1944[/img]

[/url]wierd vase by jackiesimmonds1944, on Flickr[/img]



wierd vase by jackiesimmonds1944, on Flickr



ok got there in the end!      Maybe it is because it is a "sandwich".  But no green at all.  And just HORRIBLE.   I cannot believe it is essentially the same kind of glass.

and here is another one.  This one stayed nice and green, and did not have this cloudiness or grey edges but on reflection, might just be one sheet of glass, 6mm, with broken pieces added.  

float glass bowl by jackiesimmonds1944, on Flickr
« Last Edit: February 15, 2015, 05:00:36 PM by Zeldazog » Logged
tish
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« Reply #3 on: February 15, 2015, 01:05:19 PM »

ok can i just say i love the top one  beauty is different to different ppl i guess ....ok so its not what u wanted but to me it is very pretty
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Arwynd
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« Reply #4 on: February 15, 2015, 02:26:16 PM »

I love it too, reminds me of coral Smiley
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jackiesimmonds
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« Reply #5 on: February 15, 2015, 03:15:29 PM »

well, wadya know!    Actually, I like the shape............I just don't like the grey edge.  And it looks better in the photo than irl Cheesy   Would still like to know how NOT to get that again.
« Last Edit: February 15, 2015, 03:17:49 PM by jackiesimmonds » Logged
Zeldazog
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« Reply #6 on: February 15, 2015, 05:01:51 PM »

Re the photos, when you're grabbing BB code from Flickr, you *don't* need the image code - you don't need to add anything at all, Flickr gives you exactly the code you need.
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Zeldazog
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« Reply #7 on: February 15, 2015, 05:13:43 PM »

Did the float come from the same sheet?   Actually, I know it didn't, as you said the bottom piece is 6mm, and the top one is two layers, so not the same sheet.  Therefore not necessarily the same formula, or even glass manufacturer.

Because float/window/greenhouse glass isn't designed as an art glass, it does have different tinges.  My last few sheets of greenhouse glass were 'whiter' (less green tinge) than the previous batch I bought.

I like it, but I have no idea why one would de-vitrify more than another, as I am assuming they are both going through two firings.  Of course, as you mentioned, you have no control over the firing, so that could have made the difference, but it could also simply be the difference in glass. 

Regarding it coming out clear after the first fusing, if it is devit, that does get worse over multiple or longer firings.  There's an artist who deliberately holds his work for extended periods to bring on vitrification.  Devitrification is actually crystals forming - so the more firing involved, the more they grow. 

Or did you use glue?  Too much glue can give off a black residue.  OR maybe a reaction with the silver foil. 


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shafeenan
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« Reply #8 on: February 16, 2015, 02:10:02 AM »

Well I think they are both beautiful.  No-one but you knows anything went wrong and if you are selling, bet it won't matter!
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jackiesimmonds
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« Reply #9 on: February 16, 2015, 02:27:20 AM »

thanks everyone, most appreciated.

Zeldadog....you are right...the glass came from a local glazier, ordered in advance and collected ready-cut.  So I have no idea if the 3mm pieces were cut from the same sheet. No I did not use glue.....and yes, perhaps it was a reaction with the silver foil.... 

I am glad, in a way, that it might have been the glass, rather than anything I did or did not do, such as the business about painting with borax.      I does make me feel I should pay the extra and work just with Bullseye, which can be refired a number of times without any problems - Warm-glass said it can be refired up to about 6 or 8 times! (tho having said that about cost, the last lot of float cost virtually the same as BE!  Averaged out at about 7-8 per sheet!)  Although I do like a frosted look and often do use the college sandblaster, I prefer to choose where I want to use it and when.   If all of my float pieces came out like this, I would not use float at all - it is a matter of personal choice, and while I LOVE the green look of float, I definitely do not like this greyness.

INCIDENTALLY

I looked at the Warmglass forum and found this, an answer to a very similar problem posed:
"It is not devit, but tin bloom. When you compress the tin side, it fogs up only where it is compressed. So, the solutions are either to layer up so there is a tin side down and air side up, or try using borax or spray A, and fire at least to 1400F for your slump. Float can handle that."      I shall need a mnemonic to remember this...I am hopeless about stuff like this..."tin down, air up".  Ah...found it ...consonants down, vowels up.....

one guy said having had problem after problem with float, he is giving up on it.  It is too inconsistent.

 I  plan to suggest to the tutor that she gives us a "crib sheet" about the use of float, including something about the use of borax, (although one of the WG answers said that borax does not always help) and what happens with tin or not tin.  Now that will make me popular..............

Then, I shall use Bullseye when I have used up all my float.
« Last Edit: February 16, 2015, 02:40:49 AM by jackiesimmonds » Logged
flame n fuse
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« Reply #10 on: February 16, 2015, 03:32:00 AM »

To add to Zeldazog's comments. I wonder what the used fibre blanket had been used for and whether something was burning off that. In defence of tutors, it must be really difficult to set a kiln programme which suits everyone, when people are using different types of glass and size of pieces. I've attended classes where everyone was using either system 96 or bullseye, which are both designed for fusing, and there were still programming problems. Even bullseye will devit sometimes (read their forum!!) I find cobalt blue one of the worst.

Cleaning the glass thoroughly is very important, and edges sometimes have lots of minute cavities, which may be contaminated by material from the cutting blade, these seem to attract devit.
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Zeldazog
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« Reply #11 on: February 16, 2015, 03:47:45 AM »

Jackie, try greenhouse glass, it's much cheaper and doesn't have a tin side.  I paid 3 per sheet of 24" square. 

I forgot to mention about it could have been tin bloom, sorry - although it looks quite consistent!  (one of the reasons I buy greenhouse now, no need for a tin-side detector; I only tend to use float if I have offcuts to use or am using a coated glass specifically)

As Julia says, it can be difficult to find a firing program to suit all.  On the course that I first learned about glass fusing, our tutor got some of us involved in kiln washing shelves, loading and programming the kiln, etc; it helped such a lot in understanding the whole process.


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jackiesimmonds
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« Reply #12 on: February 16, 2015, 06:25:23 AM »

I will certainly look out for greenhouse glass, thanks for the tip.   And I do realise that there can be all sorts of difficulties for the tutor - having a mix of beginners and more experienced is always difficult, and having kilns to take all kinds of glass must be a bit of a nightmare too.  I am sympathetic to all of that...just would like to know WHY I ended up with this result.

Must say...I had been wondering about what the fibre blanket had been used for before, it must make a difference.  But apparently, it is necessary to use it....   I shall experiment at home without.

thanks everyone for the input.

so much to learn, so little time.......I think this is rapidly becoming my motto!
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