Ripple between glass sheets trapped air

[Kitty]

ive been cleaning out old glass around here, stuff that wasnt suitable for the jewelry i make, and have made a bunch of smaller plates. the BE periwinkle opal had a slightly wavy texture, and i wondered if it would be a problem fusing. i decided it would be ok if i had a soak around 1235F so the top piece of thin BE would sort of settle down onto the wavy surface. well, i was wrong. you can see the air bubbles in the troughs between the "waves." how to get rid of them? i thought drilling pinholes might work, although it would be quite a few pinholes. the orange plate is 3mm periwinkle on the bottom, 1.5mm orange on top. i know it usually should be 2 sheets of 3mm, but this is an exercise in cleaning out old stuff, so i used one piece of 3mm and one piece of thin. the other picture is 2 pieces 4-1/2" square, periwinkle bottom, yellow top. had the same trapped air problem, but it's less noticeable on the smaller ones. i'm open to any ideas, including sawing them up for pattern bars. it's a lesson in learning to flatten sheets before fusing, i guess. they dont look square in these pictures, but they are. it's a cheesy little webcam. kitty.

[charlie]

ive been cleaning out old glass around here, stuff that wasnt suitable for the jewelry i make, and have made a bunch of smaller plates. the BE periwinkle opal had a slightly wavy texture, and i wondered if it would be a problem fusing. i decided it would be ok if i had a soak around 1235F so the top piece of thin BE would sort of settle down onto the wavy surface. well, i was wrong. you can see the air bubbles in the troughs between the "waves." how to get rid of them? i thought drilling pinholes might work, although it would be quite a few pinholes. the orange plate is 3mm periwinkle on the bottom, 1.5mm orange on top. i know it usually should be 2 sheets of 3mm, but this is an exercise in cleaning out old stuff, so i used one piece of 3mm and one piece of thin. the other picture is 2 pieces 4-1/2" square, periwinkle bottom, yellow top. had the same trapped air problem, but it's less noticeable on the smaller ones. i'm open to any ideas, including sawing them up for pattern bars. it's a lesson in learning to flatten sheets before fusing, i guess. they dont look square in these pictures, but they are. it's a cheesy little webcam. kitty.

go slow when you have non-flat glass. something like:

whatever to 1150
soak 30
50/hr to 1250
soak 15
500/hr to 1480
anneal

and you'll still get some bubbles.

[Kitty]

TY charlie. i was sort of close to what you suggest, but i guess i should have gone even slower: i did this:

300 to 1235, H 20
500 to 1500, H 10
etc.

i was hoping the soak at 1235 would let the top flex enuff to meet up with the bottom, but it was wrong.

if i get anymore glass like this again, i'll flatten the sheets before using them.

[Tony Smith]

Kitty, hold longer at your top temp... I've been getting away with a 20 minute hold at 1480 for System 96 to get a relatively smooth surface, but I had done a test and held for as long as 90 minutes to get the pesky little bubbles to smooth out completely.

Tony

[Kitty]

tony, did the bubbles come thru the surface? you can see in my pix that there are sort of trench marks with bubbles in those trenches. i wish i had flattened the bottom sheet before i put this stuff together. ah me.

[Tony Smith]

Hi Kitty,

No, the bubbles didn't come to the surface... in fact they are still there, just flatter/smaller/less noticeable which on opals isn't as much of a problem as a surface that looks like it has the mumps.

Tony

[Kitty]

oh, i see. thanks for clarifying!
that'll give me an idea should this happen again.
i'm using up glass that i've had for years that doesnt sell as jewelry, and this particular opal periwinkle was the culprit, both sides. one side had trenches, and the other side was pretty heavy cat's paw, which produced it's own bubbles, but less unattractive that the orange ones. the second plate has them sort of evenly distributed. not that i would ever try to achieve such a result....

[Brian and Jenny Blanthorn]

ive been cleaning out old glass around here, stuff that wasnt suitable for the jewelry i make, and have made a bunch of smaller plates. the BE periwinkle opal had a slightly wavy texture, and i wondered if it would be a problem fusing. i decided it would be ok if i had a soak around 1235F so the top piece of thin BE would sort of settle down onto the wavy surface. well, i was wrong. you can see the air bubbles in the troughs between the "waves." how to get rid of them? i thought drilling pinholes might work, although it would be quite a few pinholes. the orange plate is 3mm periwinkle on the bottom, 1.5mm orange on top. i know it usually should be 2 sheets of 3mm, but this is an exercise in cleaning out old stuff, so i used one piece of 3mm and one piece of thin. the other picture is 2 pieces 4-1/2" square, periwinkle bottom, yellow top. had the same trapped air problem, but it's less noticeable on the smaller ones. i'm open to any ideas, including sawing them up for pattern bars. it's a lesson in learning to flatten sheets before fusing, i guess. they dont look square in these pictures, but they are. it's a cheesy little webcam. kitty.

Yo Kitty

What is happening is once U trap the bubbles then they expand n the glass gets softer so compounding the problem

The solution is a slow temp rise B4 the glass softens n mayB a soak as well

This alowes the air 2 escape n any air trapped has less air in it

I only use flat glass so the problem is less

I dont recall in this thread chads small bits of glass on the 4 edges

This will help the centre 2 go first

I go 50 c hour to 700 c then 20 c hour till done

U will probablly need 2 start bellow 700

And as said I expect U will still get bubbles

Brian

[Lionel]

Secret tip number 1 - How to NOT trap bubbles between sheets.

1. Cut 1/4" strips of clear BE or your fusable.
2. Cut 1/4" squares from your 1/4" stips.
3. Place them all on fiber paper and melt at 1450 for 20 minutes
You should have little round dots - you can kill your kiln after the
melt because there is no annealing required.
4. Place the CLEANED round dots between the layers in each corner
1/2" in from all edges.
5. RA1=450 to 960 hold 60 for 2 layes
RA2=900 to 1450 hold for 30
RA3=1500 to 960 hold for 60
RA4=70 to50 hold for 60
If you hav an all IFB kiln - Kill Power
If you have a Fiber kiln - RA5=70/HR to 200 then off

This causes the middle to drop first and the corners last.
No chance to trap air.

All kilns run a little different - you will need to play with this - but it works.

[Lionel]

oops

RA4=70 to 850 hold for 60

[Jackie Beckman]

Secret tip number 1 - How to NOT trap bubbles between sheets.

1. Cut 1/4" strips of clear BE or your fusable.
2. Cut 1/4" squares from your 1/4" stips.
3. Place them all on fiber paper and melt at 1450 for 20 minutes
You should have little round dots - you can kill your kiln after the
melt because there is no annealing required.
4. Place the CLEANED round dots between the layers in each corner
1/2" in from all edges.
5. RA1=450 to 960 hold 60 for 2 layes
RA2=900 to 1450 hold for 30
RA3=1500 to 960 hold for 60
RA4=70 to50 hold for 60
If you hav an all IFB kiln - Kill Power
If you have a Fiber kiln - RA5=70/HR to 200 then off

This causes the middle to drop first and the corners last.
No chance to trap air.

All kilns run a little different - you will need to play with this - but it works.

In my experience, if you place the chads 1/2" in from the edge, you'll trap air and actually cause bubbles right around them. The way Brock teaches this is to place the chads directly at the edge of the piece. Also, when I've made them, I run the kiln up afap to 1500 or even 1525 to get them round, then off.

I don't understand the 60 minute hold at 960 on the way up. Are you trying tto equalize the temp at that point, or what? I usually do that at a higher temp, but perhaps your way works equally as well.

Generally 450 an hour ramp up may be a little too fast for most pieces - especially larger ones. I'd say you're much safer at 300, and depending on the piece, I often go slower than that.

Your rate 2 of 900 degrees an hour seems a very odd way of eliminating bubbles. That fast a rate is sure to trap air. Those who squeeze air out from under a clear cap have learned to go much slower from 1100 or 1150 up, and often add several soaks in this range or a little higher.

Although I don't do this in my current work, I used to cap everything in clear - and I mean the most uneven stacks of glass you can imagine, from two layers to seven layers in the same piece, and I don't think your method would have worked well for me. But I guess if it's working for you - thats great. I just thought I'd forewarn others that it doesn't seem quite right to me. (No offence personally intended)

Jackie

[Geri Comstock]

A few years ago, after I read Gil Reynold's article some time ago about his squeeze technique for preventing bubbles with Spectrum, I did a little experimentation on my own with BE glass. Here's the final results...

In my kiln, the fastest I ramp is 450F per hour and that's only for cabs. Everything else is 350F per hour or less, depending on size and thickness. To remove bubbles I do a 30 minute hold at 1180F on the way UP and then finish ramping to the top temp. On the way down, I always anneal at 960.

I've passed this along to other people and they're reported needing to change the schedule somewhat for their kilns. Some have a longer hold at the "squeeze" temp...45 minutes to an hour instead of 30 minutes. Some lower or raise the squeeze temp by 5-20F for better results in their kiln.

All kilns fire differently, so you'll probably have to try several different combinations to find the "magic" one for your kiln.

And of course, a few libations to the kiln gods never hurts.

Geri

[Lionel]

Thanks Jackie

I like the word "chads" - I never did know what to call those things.
If you put them at the very edge you run the risk of moving the edge out and distorting it. Lets split the diffferance and say 1/4".

Using the soak at 960 on the way up equalizes the kiln shelf and bricks. The kiln ramps faster to the higher set point and recovers to that temp faster when you crash it.

A 5 year old Paragon GL64 with original elements will ramp slower than a new kiln. It's kind of like running a 64 Olds in the winter. You'll get there but it will take a while.

After a year of devit problems - I've found that the less time in the 1000 range is best. I agree with adding soaks above 1200. I don't do it because my kiln is slower than most.

I guess my last line about "playing" with it was'nt strong enough. There is as much to learn from mistakes as successes. I have a log book I use with a photo of all my %&(* up's and I'm on page 337. If this board was around 15 years ago it would be below a 100 I guess.

I never take personal offence from good information and your caution flag to other is waranted. It's easy to assume that everyone who reads this stuff is on the same page. This problem was on page 91.

[Jackie Beckman]

Thanks Jackie

I like the word "chads" - I never did know what to call those things.
If you put them at the very edge you run the risk of moving the edge out and distorting it. Lets split the diffferance and say 1/4".

Using the soak at 960 on the way up equalizes the kiln shelf and bricks. The kiln ramps faster to the higher set point and recovers to that temp faster when you crash it.

A 5 year old Paragon GL64 with original elements will ramp slower than a new kiln. It's kind of like running a 64 Olds in the winter. You'll get there but it will take a while.

After a year of devit problems - I've found that the less time in the 1000 range is best. I agree with adding soaks above 1200. I don't do it because my kiln is slower than most.

I guess my last line about "playing" with it was'nt strong enough. There is as much to learn from mistakes as successes. I have a log book I use with a photo of all my %&(* up's and I'm on page 337. If this board was around 15 years ago it would be below a 100 I guess.

I never take personal offence from good information and your caution flag to other is waranted. It's easy to assume that everyone who reads this stuff is on the same page. This problem was on page 91.

I can't take credit for the word chads. (To me, chads are still the reason we ended up with "W." ) A while ago, on the old board, there was a discussion about these little glass pieces, and some called them beads, some called them chads, and I think some even called them "Brads" until the real Brad objected. Whatever they are called, I always trap air with them when they are too far back from the edge. And like you said, placing them too near the edge causes a wavy effect arount the perimeter. Brock uses that as a design element, or it can just be ground off when coldworking.

I wonder why you're getting devit at the 1000 degree range. That seems low to me to be getting devit. What glass are you using? I haven't had too many devit problems, but lately I surface treat (grind, polish sandblast, etc.) just about all my work anyway, so I don't fire up fast or crash cool in attempts to avoid devit. Even when I used "naked" uncapped opals, I only noticed problems occasionally, and only with certain colors.

So, are you saying that your rate of 900dph doesn't trap air? I guess those little chads must be doing their job!

Take care,
Jackie

[Kitty]

i only tried chads once, just as described in this thread, and got bubbles the size of dimes over each of the chads. so much for that technique on my end.

i should have flattened the wavy glass first, rather than trying to use it the way it was. lesson learned.

the devit is happening on the pink opal and orange. yellow seems ok, and sky blue (periwinkle opal) so-so. i dont crash-cool the kiln. it seems the light pink opal is particularly susceptible. also, this glass is six years old, so maybe its formula is different. dunno.