Haze on Drop

[lbailey]

So I've been making drop bowls lately with pretty good results. Different designs, some screen melts, others with strip edge, etc. But sometimes I get a pale white haze on the top 1/4 of the piece, all the way around. It is more visible in the darker opal glasses but is also on Tekta and transparents. Seems to happen more often with the larger diameter and taller drops.

I use ceramic drop rings with MR-97, mostly 6" or 8" diameter, dropped 4" to 6". Typical schedule:

Rate/Temp/Hold
200/500/:10
200/1100/:10
100/1300/:10 (average, skip when the bottom is just short of the desired shape)
AFAP/900/2:00 (vent to 1100 first, slowly)
100/700/off

Maybe the last few inches of glass that drops through the ring is pulling some Boron Nitride with it, embedded in the glass? Before each use I lightly brush the ring to remove any loose powder, blow it off with low pressure air, refresh with a very light mist of MR-97, let dry for 10 min. (It doesn't appear to be too thick or uneven).

Thoughts, suggestions?

[lbailey]

Looking for some feedback here, no one has seen this before or just don't use MR-97 on drop rings?

Thanks

[Stephen Richard]

I know you want an answer to your question, but there is nothing there that really shows up as a possibility in the information you give. So I suspect the difficulty lies in something you have not mentioned. The one thing that occurs to me is cleanliness. It does not happen all the time, so maybe some cleaning is better than others. Perhaps the kiln is cleaner sometimes than others.

[Kevin Midgley]

Not everything in life is for free free. Sometimes thousands upon thousands of observations and notes are required to find a solution to a production problem. Sometimes people don't wish to give that information gained through experience away for free and besides, what works in one kiln, may not work in another so called identical kiln somewhere else. You could easily be given wrong information here on this board by well meaning individuals who may or may not have worked out the variables to doing something similar to what you want to do in your kilns, but in their kilns.
So rather than leading you astray people stay silent.
Seriously though if you paid someone like Brock or Stephen, or Brad or myself a consultant's fee to hand hold you via skype, you might, but not guaranteed, get a solution to the firing problems you face a little sooner than if you try doing it on your own. Either way you will be playing detective, making the observations and notes. Firing experience is not obtained for free.

A free example of a variable. The electrical service to my town is being upgraded. The past few months the battery backup on the computer was regularly reading 122 or even 123 volts. Cheap fast kiln firing. Today when I look, and we are experiencing cold weather, I get a reading of 117 or 118 volts. Much less power. Everyone is using more electricity to keep warm.

[lbailey]

Thanks Richard, I understand your point but frankly don't have any other facts to share. I'd take a picture but it is very faint and only in the top 1-2" of a 6" high drop. The smaller/shorter drops don't seem to suffer from this effect so it may have something to do with the size. All glass is carefully cleaned/rinsed/dried before placing in the kiln.

Have you seen MR-97 pulled into moving glass in other circumstances or set ups? I think it may have something to do with that.....

Thanks

[Valerie Adams]

Without photos it's pretty hard to help diagnose a problem. What's 'haze' to one person might be 'scum' to another and 'devit' to yet another.

I've not seen MR-97 pull off a mold and move into glass. I have seen it leave a powdery white residue on my glass which simply wipes off. If it doesn't clean off and it is indeed MR-97, then you could try a white vinegar soak and/or scrub with a green Scotch-brite type pad.

Most likely, what you're seeing is distortion in the glass caused by it stretching and moving. Even regular slumped pieces can have some 'frosted' looking stretch marks.

But again, without a photo, who knows?

[becky wills]

I do a lot of drops...i would not use Boron on these...just kiln wash...mind you...are you saving the rim or not...i cut all mine off anyway. If you are leaving the rim on i imagine it would be annoying. Fibre paper also leaves a lot of scum under the rim.