which bullseye opals stripe when fired on edge?

[alyssa oxley]

ya know, like french vanilla, or deep red does it. i am not about to buy/test every opal. do any blues, greens or oranges do it? thanks.

[Stephen Richard]

This is a link to a copy of The Bullseye table on reactive glasses
http://www.stained-glass-supply.co.uk/M ... ential.pdf

[Brad Walker]

As I understand it, Alyssa's question has nothing to do with reactive glasses. It has to do with the tendency of Bullseye's opaque glasses to show a different color on the inside than the outside when turned on edge and fired. For example, strips of French Vanilla can show two colors when fired side to side on edge, a lighter white and a darker off-white.

The aventurine greens (and probably the blue as well) do something similar. They're fascinating laid on edge and fired. Some of the dark opaques do something similar, but in my experience nothing is as pronounced as french vanilla or aventurine green (especially the lighter one). I've found some variation from sheet to sheet, even with the same color.

For a reallly interesting effect that's similar but different, try using some of the two-color streakies on edge, especially the two-color opals, such as red and white 2124.

[alyssa oxley]

yes, i see i did not state this clear enough. sorry stephen. and thanks. i am trying to determine the opals that do exactly what brad is talking about. a single color that essentially reacts with itself. i will take a look at the streakies, but i am after a very "plastic" effect. not sure that will produce it. maybe it will be better! the rest of you, keep wracking your brains. if that striping happens, let me know. thanks again.

[Brad Walker]

a single color that essentially reacts with itself.

I don't think there's anything reacting. I think it's just that some of the color (usually darker) migrates to the outside of the strip, while the lighter colors remain in the middle.

[alyssa oxley]

yeah, it just looks that way. thanks brad.

[Valerie Adams]

I believe it's the textured side of Bullseye's opals that have a very thin layer of clear glass on them; that's why sometimes it's recommended that you cut on the textured side if you have trouble cutting an opal. I'm hoping someone with more knowledge on the subject chimes in here but I seem to recall having read this somewhere.

[Bob]

Hi Alyssa,

I don't know if this is relevant or current so take it for what it is worth. In the early days of the WGBB Lani discussed the striping that can appear with opal glass. She noted that when you look at the top surface of a sheet of glass it was one consistent colour. However when you looked at the edge it had the thin striping of different colours that made up the overall colour of the glass. She said that Klaus Moje used this characteristic to get the very fine striping of colours that showed up on the surface of his strip cut bowls. I had seen Moje's pieces in galleries and museums and had noted the extremely delicate striping on the surface. Lani's explanation always stuck in my mind. A great example of using the character of the materials in the design.

I guess one way to answer your original question would be to examine the clean cut edge of the glass to see if there is striping. If Bullseye's manufacturing process has changed then that subtle layering may not exist any more.

You could create the striping by using powder wafers as patches between the layers of glass. That is what I did in the green base on the http://www.leatherbarrow.ca/sculptures6.html. If you did the same with wafers between sheets of opal glass there would be faint striping between the sheets. Or you could make your own striped glass by laying multiple layers of say various blue wafers on a base of thin blue opal. Just some thoughts.

Cheers,

Bob

[Tony Smith]

I've seen this effect on some of the reds as well. It wouldn't surprise me if the effect is from exposure to oxygen during the rolling and annealing process. We may be seeing a slight chemical change on the exposed surfaces due to oxidized lead, or whatever chemical that contributes to the glass color.

Tony

[Stephen Richard]

As I understand it, Alyssa's question has nothing to do with reactive glasses. It has to do with the tendency of Bullseye's opaque glasses to show a different color on the inside than the outside when turned on edge and fired. For example, strips of French Vanilla can show two colors when fired side to side on edge, a lighter white and a darker off-white. ......

Thanks for the correction Brad.
Cheers

[Susan Cox]

Hi Alyssa
Spring green always has the thin stripe for me

[haleybach]

I have been playing with designs using those thin strips of color with Bullseye glass.

Not a reaction between two glasses, rather a quality of the glass that appears from my tests to be related to heat work.
If I had to guess I would say it is individual ingredients in the sheet that do not fully blend until fused. It is the same on both the smoother and rougher sides, and as noted by Bob above sometimes visible on the cut edge of glass before it goes in the kiln.

I'm getting good results from very soft fuse temps.
My kiln full fuses 6mm at 1475/8
My 'normal' soft fuse I take up to 1420/5

My best tests of these are at 1400/1

Still playing with it. This would go so much faster if I had half a dozen kilns to test in and a much wider variety of glass on hand

I'm very new at this fused glass OCD thing.

[Morganica]

I think heatwork is closer to the mark--the color changes on the surface when it's dumped onto a cold marver and flattened with a roller. The contact "chills" the glass, essentially freezing it into position with that color. The interior of the sheet cools more slowly, so the color has longer to mature. When you refire the glass, you typically cool it pretty slowly (and as evenly as possible), so there's a much better chance that the colors will completely mature and even out.

It also depends on the degree of heatwork, which can be fun to play with--I get a "tweed" effect when I tack-fuse striking glasses, to the point that I can map hot and cold spots in the kiln with it. I suspect, therefore, that you'll get better striping of any opal glass with reduced heat. I know I can reliably get French Vanilla (of course) to stripe until the second full-fuse firing, and Marzipan will stripe with a minimal fast fuse, but to keep the stripe in Light Peach Cream you must only tack-fuse and then it still should be a cool firing. Opal orange can keep a thin orange edge, usually on one side more than the other (don't ask me why)...but again it has to be a light fuse.

Hmmmm. Now I need to go play around with this...

[haleybach]

I tested the heat work theory a bit. I had a bunch of grey and blue strip pieces in my scrap bins so those are what I've tested.

All four grey colors give a blueish to teal stripe of varies intensity. The color is most noticeable, of course, when the same shade is next to itself. However any grey next to any other grey has a visible stripe. Not as thick as French Vinalla gives, more of a pinstripe. Deco gave me the strongest result.

First test I fired to 1400 with a 5 min hold, extended the anneal. About a 4x6 piece.
Second test, I cut an edge off the first piece and fired it again to 1420 for 5 minutes. The blue/teal stripes faded but are still there.

Third test was with more blues and is cooking now.

BTW- in my kiln I call 1470 hold 5-10 a full fuse and 1350 with no hold a tack fuse. I'm still looking for a 'soft' fuse I really like.

[Havi]

Hi all,
Strangely enough I just finished making a stripe fused sheet, with "ice cream " colors, opaque.

I noticed that BE 0421, petal pink has the same phenomenon, like French vanilla, darker stripes on the side.



Havi

[Valerie Adams]

I KNEW I had recalled someone at Bullseye saying that there's a transparent layer on the textured side of opals, which is why we're told to cut on that side if we're having cutting troubles!

At BECon recently, one of Rudi Gritsch's slides showed the phenomenon in a side-view enlargement, along with the caption: "Transparent layer on surface from cooling quickly in production."

[Nina Falk]

Valerie is right. there is a thin coating of clear, on the surface of FV. that's why some people sandblast it off, to increase the reaction with dense white or turquoise, etc.