Float Glass won't fuse

[Sharon the Cat]

Hi, I'm new here & will get straight in with a problem.

I have been experimenting with very basic float glass snowflakes. They are 3mm glass from a window with a copper wire inclusion as a hanger & originally some gold flakes but they fell off!

See pic below.

I like the devitrification because it makes the snowflake look frosty but I cannot get it to actually fuse.

So far I have tried to fire them 4 times, as follows.

1]
Segment   Ramp Rate (ºF/hour)   Target (ºF)   Hold (minutes)
1   250   1100   15
2   200   1245   30
3   9999   1510   15
4   9999   1100   35
5   150   900   0

Try 2] holding for 5 more minutes on segment 3

Segment   Ramp Rate (ºF/hour)   Target (ºF)   Hold (minutes)
1   250   1100   15
2   200   1245   30
3   9999   1510   20
4   9999   1100   35
5   150   900   0

Try 3]   

Segment   Ramp Rate (ºF/hour)   Target (ºF)   Hold (minutes)
1   250   1100   15
2   200   1245   30
3   9999   1520   22
4   9999   1100   35
5   150   900   0
 
4th attempt

Segment   Ramp Rate (ºF/hour)   Target (ºF)   Hold (minutes)
1   250   1100   15
2   200   1245   30
3   9999   1550   20
4   9999   1100   35
5   150   900   0

I've cooked them so much the copper wire has burnt through.
My kiln is a Skutt Firebox & I would appreciate any advice from the knowledgeable out there.

[flame n fuse]

Hello Sharon
I've never fused float glass, but it sounds as if your programmed temperatures should be within the right range. Have you used this kiln before ? (I'm wondering if the temperatures are reliable).

[Sharon the Cat]

Yes, I've used it very successfully with both Bullseye & other float projects.

When I tack fused float it took me a few tries to get it right with a certain softness to the edges but this has me stumped.

[silkworm]

With my firebox on its auto fast and full which it states to be 1465 I get a mid fuse on float. Were you wanting a full fuse or are the pieces not sticking together?

[Zeldazog]

I wondered the same as Silkworm - do you mean they're not sticking, or do you mean you want a full fuse?  They look nicely tacked to me?

1550F is 843C which is about what I do a full fuse of float glass at.

Are these pieces that you've re-fired several times?  Or tried different pieces at the different temperatures? 

If they are ones that have been back in several times, I'd guess that they're now beyond re-working, as the devit will probably be doing something to stop it fully fusing together.  Try using the 4th schedule with a new batch.  Or even one on its own if you don't want to waste loads more time cutting lots of snowflakes (kilns cost a lot less to run than you think)

Are you sure it's float glass, did you buy it from a store or could it be from a double glazed window?  If so, could you be working with K glass or E glass, that's a very even de-vit you're getting there otherwise?  Actualy, for float, it looks very 'water white' float normally shows quite a green tinge - is it possibly Optiwhite, which I've never tried working with but I wonder if it fires differently due to it's altered formula?

[Zeldazog]

Although this was only tack fused, I find it very difficult to get a full fuse to the treated side of Pilkington K/Planibel E glass (to the point I stopped trying)

[Sharon the Cat]

Some good points there, thanks to everyone who responded.
To try and answer all points in one go.

When I said fuse I meant full fuse not tack fuse. As I mentioned I have tack fused float glass no problem & these are most certainly tacked, sorry I thought you could see this in the photo.

All pieces fired 4 times. I was wondering if the devit somehow was holding the form so that it couldn't draw up properly.

I've looked back at my records & the first fuse was in fact a tack fuse because I needed another piece of float tacked urgently. There was no devit after tack fuse & they were tacked OK.

The second firing was supposed to be a full fuse & this is where the devit appeared. The devit seemed to increase with each firing.

I have no idea what the glass was originally, it could have been window, greenhouse or double glazing, but I doubt if it was Pilkington K. The original pieces of glass did have the green tinge to the edges.

When I first tack fused float it took 4 attempts for the edges & points to soften enough, I got some devit but not as much. My second attempt was right first time using the 4th attempt firing schedule.

My biggest problem is patience. It seems as though I just have to learn from experience with this one. The trouble is I hate to throw any glass away, even if was a feebie. Any ideas as to what I can do with 3 failed snowflake experiments???

[Pat from Canvey]

You might try using devit spray and see if that helps, see http://www.warmglass.com/making_your_own.htm

[Zeldazog]

http://When I said fuse I meant full fuse not tack fuse. As I mentioned I have tack fused float glass no problem & these are most certainly tacked, sorry I thought you could see this in the photo.

I thought it looked like it had tacked quite well, that was the confusing thing as you said it hadn't fused.  

http://All pieces fired 4 times. I was wondering if the devit somehow was holding the form so that it couldn't draw up properly.I wondered that.

http://The second firing was supposed to be a full fuse & this is where the devit appeared. The devit seemed to increase with each firing.

1510F = about 821C - I only get tack fuse at that.

Once devit has started, it will get worse each firing, as it's where the glass has crystalised, and the crystals will grow.

http://I have no idea what the glass was originally, it could have been window, greenhouse or double glazing, but I doubt if it was Pilkington K.

If it did come from a double glazing unit, why do you doubt it could be Pilkington K?  It's been used in DG units for years.  

[Zeldazog]

My biggest problem is patience. It seems as though I just have to learn from experience with this one. The trouble is I hate to throw any glass away, even if was a feebie. Any ideas as to what I can do with 3 failed snowflake experiments???

Am much the same, hate to throw anything away.  However, after nine years of fusing, I really need to think about getting rid of something things! 

[Sharon the Cat]

http://When I said fuse I meant full fuse not tack fuse. As I mentioned I have tack fused float glass no problem & these are most certainly tacked, sorry I thought you could see this in the photo.

I thought it looked like it had tacked quite well, that was the confusing thing as you said it hadn't fused.  

My abbreviations I use to myself Tack = tack fuse, Full = full fuse, Slump = slump. Why use 2 words where I know what one means?

The second firing was supposed to be a full fuse & this is where the devit appeared. The devit seemed to increase with each firing.

1510F = about 821C - I only get tack fuse at that.

At what temperature do you normally get a Full Fuse with float?

http://I have no idea what the glass was originally, it could have been window, greenhouse or double glazing, but I doubt if it was Pilkington K.

If it did come from a double glazing unit, why do you doubt it could be Pilkington K?  It's been used in DG units for years.

I know the house concerned & if it came from double gazed units it would have to preceed those in place which have been there for over 20 years, & Pilington K I believe has been around for 21 years ish. Do you know if Pilkington K causes particular problems?

Perhaps I will be verrry brave & consign 3 first attempt experimental snowflakes to the bin.

[Zeldazog]

Depends if you consider a beautiful, sometimes, white, sometimes pink/green iridescent effect a problem :-) 

But the coated side will repel and the only way I've been able to get anything to full fuse to the coated side of K or E glass is to make sure it's covered completely and overlapped with the non-coated or plain float glass.

As said in an earlier post, I full fuse at 843 deg C and that gives a nice rounded edge with float or greenhouse glass.


I wonder if K glass was the first low emissivity glass?  Certainly the most well known I guess, but I have no idea if they were the first - a quick look on Pilkington site and it doesn't shout about being the first to develop it, so perhaps the glass was still coated with something?

Either way, I find the older the glass, the more issues I get with de-vit.  Someone gave me some old glass from their house, and that has gone cloudy, like devitrification without even going in the kiln!  Be interesting to see how that fires, although I am not looking forward to cutting it, expecting a few not going so well....

I personally like the fact that they're not fully fused, but I guess if that's not what you planned then you aren't going to be satisfied. 

Glass fusing certainly is a waiting game, not just because of the length of the firing cycles, but that "will it work this time, were the kiln fairies kind?" questioning doesn't go away! 

[Pauline]

I'm not much of a fuser but have done some pieces with bottle glass and like this site
http://glasswithapast.com/recycled-glass-firing-schedules/

I haven't done any window glass but thought you might be interested

[Sharon the Cat]

Thank you Pauline.  I originally read up on higher temperatures for float glass on that site.
It is great source of information.

[Decorative Glass Supplies]

This is a common problem when using float glass from he local merchants. Unfortunatly the second and hird generation thermal efficency glass have a higher quality coating and is not always decrnable and as more 3mm glass is being used this will become an increasing problem You used to be able to detect using a magnetic light but since the composite of the coating has altered it is not so readily identified. Can I suggest that if it is 3mm that you are going to need that you look at horticultural float glass it is 3mm thick and can be identified with a slight oragnge peel finish. THis is npot coated and will be considerably less expensive or alternativly go for a sheet glass.
I hope this helps