Haze with irid clear

Cliff Swanson · Post by **Cliff Swanson** » Sat Apr 26, 2003 7:24 am

I've fired 2 pieces for which one layer of the 6 mm blank was Uro granite clear irid (S96). In both cases there is a very slight haze that is visible when the piece is held up to light. What is this, and how might I prevent it from happening in the future?

Any thoughts appreciated, thanks in advance,

Cliff

Steve Immerman · Post by **Steve Immerman** » Sat Apr 26, 2003 7:52 am

Is the irid facing up? Facing down? or between layers?

Is the haze on the surface or between layers?

Steve

Cliff Swanson · Post by **Cliff Swanson** » Sat Apr 26, 2003 8:20 am

The most recent blank was fired with irid on top facing up, the previous one was fired with the iridized sheet of glass forming the bottom layer of the blank and oriented so that the non-coated surface contacted the shelf. The hazing was more prominent in this configuration than the more recent one with irid sheet on top and coating upward. Hope that makes sense. BTW, process to the full fuse was 400 dph/1000/0; 60 dph/1250/0, 400 dph/1430/10 min; anneal.

Thanks,

Cliff

Patty Gray · Post by **Patty Gray** » Sat Apr 26, 2003 9:16 am

Hi Cliff,
Are you fusing on kiln washed shelf, thinfire or fiberboard? Thinfire can cause a hazing at times which normally goes away during the slump firing. By chance have you been firing lusters in your kiln? Sometimes the lusters can collect on the elements causing contamination in other firings. Good luck. Patty

Phil Brown · Post by **Phil Brown** » Sat Apr 26, 2003 9:18 am

Cliff,
by any chance did you use fiber paper for this? I have gotten unremovable white haze on pieces fused with some fiber paper I tried. Unfortunately my supplier can not trace its origins so I can't determine a brand name for it. The paper was fully burned out first. The kiln was very well vented and even happened on a third firing so I don't think it could have been binder burnout at that point. It wasn't Thinfire BTW. The worst one was with Uro 96 1/4" clear as a base. I could not find any chemical that would remove the haze including Phosphoric, Muriatic acid and extended brushing with abrasive cleanser (not at the same time). Maybe someone can answer both of these dilemmas. I've been meaning to post about this and see if anyone had any ideas.
Phil

Cliff Swanson · Post by **Cliff Swanson** » Sat Apr 26, 2003 9:38 am

Thanks for the replies so far, I appreciate them. Of course these situations are never simple, as evidenced by the questions related to information I forgot to mention. I fire on a BE kiln-washed shelf, no thin fire or fiber paper. I haven't fired any lusters...I have fired Hanovia gold and platinum as a medium for signing my work, but there have been other firings between the last one involving the metalics and the hazing of the irid pieces, so I don't think a residual vapor is the issue. The only thing in common between the two pieces that have developed the haze is that they both involved granite irid clear. I have to emphasize again that the effect is subtle, only visible when the glass is transilluminated by back lighting, and only on the areas of glass where the irid is located (ie. no hazing of the border of the piece where there is no irid).

I've seen reference to "irid scum" in previous posts...I wonder if this is possibly what I'm seeing.

If so, how does one control it's emergence in a piece.

Any other ideas appreciated.

Cliff

Tony Smith · Post by **Tony Smith** » Sat Apr 26, 2003 10:12 am

Cliff,

How are you cleaning your glass? Anything different there? I started washing the glass with windex then rewashing with distilled water after. I haven't seen any haze cleaning that way. I was using isopropyl alcohol for a while until I noticed it was leaving a film behind.

Tony

charlie · Post by **charlie** » Mon Apr 28, 2003 10:49 am

i've had this happen on uro 90 irid also. not on the irid side, but the reverse. i had blasted a pattern into the irid side, and cleaned that side with isopropal alcohol, but not the non-irid side.

cynthia asked a while ago about it on uro 90 clear, and the conclusion was something on the rollers as it had a distinct pattern to it.

Steve Immerman · Post by **Steve Immerman** » Mon Apr 28, 2003 12:15 pm

Cliff,

Sorry if I'm being dense, but I still don't understand if the haze is on the surface or between layers.

Steve

Cliff Swanson · Post by **Cliff Swanson** » Mon Apr 28, 2003 8:55 pm

Steve,

Density notwithstanding...

... It's a bit hard to tell because of the texture of the granite glass, but I'm pretty sure it's on the non-irid surface, consistent with Charlie's observation. In both cases that surface is between layers.

A weird thing related to this happened this weekend. I refired the second piece that hazed because I was doing a tack fuse of some other design elements, and upon inspecting it, I think the haze is less noticable now than it was after the full fuse when I first noticed it. I had cleaned it well before my original post about this, and I don't think the reduction in haze has anything to do with a better cleaning job on my part after the second firing. The first piece on which this appeared was fired 3 times, I noticed the haze after the first firing, and it didn't diminsh in subsequent ones.

Curious.

Cliff

Lynne Chappell · Post by **Lynne Chappell** » Fri May 02, 2003 1:39 am

I've had Uro 96 irid clear haze before and I was never sure why. I think I decided that that particular sheet wasn't any good. Other sheets have been fine. I've had irid sheets of the "other" glass do weird things too, like pock marks but it seems always to be a particular sheet. Maybe there's just something in the process in the factory that isn't consistent and can cause some kind of contamination.

WarmGlass.com

Haze with irid clear

Haze with irid clear

was it fiber paper?