Bubble trouble

[Jon Markovic]

Hi all,
I have tried to make a piece with an air bubble trapped in squares formed by stringers.
To do this, I tack fused stringers in parallel lines at regular intervals, on two pieces of glass, then fused the two pieces together having turned one through 90 degrees with te stringers sandwiched by the base glass on either side.
I was hoping to find a single bubble set in the centre of each square (formed by the stringers) but instead have ended up with four smaller bubbles, one in each corner- see atached image.
While it looks nice (to me, at least) it is not quite the effect I was wanting.
The fusing schedule I used is the preprogrammed medium speed full fuse programme for Skutt / Glassmaster kilns using COE96 glass. ie 350F per hour to 300F, hold for 10, then 600/1645/10, then AFAP/950/30 then 150/800/10
Any ideas on how I might modify this to achieve the desired effect??
Thanks,
Jon

[Brad Walker]

Can't see a photo, but my guess is that you put the stringers too far apart. A bubble will split into multiple bubbles if that's the case.

For larger bubbles you need more height between the two layers. For example, 2mm stringers can create larger bubbles than 1mm, and 3mm glass larger bubbles still.

[Jon Markovic]

Thanks Brad; much appreciated.

I'd missed that the original photo did not upload properly, so I have reposted this, in a smaller file size.

The stringers were 1mm diameter and set at 10mm centres.

I will try again with stringers set more closely together.

[Brad Walker]

The stringers were 1mm diameter and set at 10mm centres.

I will try again with stringers set more closely together.

My rule of thumb is that with 1mm stringers you need to be around 3mm apart. Any further and the bubble will start to split.

[Jon Markovic]

Great thank you!

Do you have a view on how hot the glass needs to be to generate the bubble effect?
I ran to full fuse last time, but wondered whether a contour or even tack fuse would suffice, as this would cause less loss of definiton of the stringer..

[Brad Walker]

1350F or higher should work.

[JestersBaubles]

I think you are fusing to too high of a temperature. 1645 deg F is HOT for full fuse. The glass is flowing at this temp (in its cute little viscous way ) Normally you would go to about 1465-1480, depending upon the glass.

Dana