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Too close to the fire?

Something new to me, but then I had never done a wire melt in this small kiln. The melt cracked during cool down because it was welded to the kiln shelf at the outer edges of the melt. The kiln is an Olympic SQ146 220 volt, 14” x 14” x 6” with top and side elements that are wired in series and therefore, both are on at the same time.

Apparently the 15 coats of kiln wash were not enough to withstand the close proximity to the side elements for the extended time of the melt cycle. The glass flowed out to within about 3” of the side elements at 1685 degrees for 90 minutes. The glass did not stick to the shelf in the center, but at the edges it stuck so well that I have lots of small divots in the kiln shelf. I expect the kiln shelf is also toast unless I can turn it over.

Sounds like you've just made yourself a whole bunch of mullite dams. My condolences, but if you cut up the dinged shelf with your tilesaw you'll get some nice dams.

I've not had a ton of luck with kilnwash-only at those temps/times; the only sure-fire protector I've ever found is 1/8 inch fiber paper (or pouring a plaster/silica basin and using that instead). Probably the closer the glass got to the side elements the thinner (and hotter) it became, and there went your kilnshelf. Sometimes you can put a layer of clear irid down underneath the melt, irid-side down, and get a little less sticking, but then you've got to contend with bits of irid floating up and looking like scum on the surface, too.

All in all, the fiber paper just works better.

Yes Cynthia, I was lucky to read this advise of yours prior to doing melts.

I always use fiber paper on the shelf before doing the melt. It works for me.



Many thanks for that, (as well as other good advises)


Havi

Mark, I learned that fiber paper is the way to go the same way you did.
However I needed dams anyway.

This event motivated me to drive all the way down to the ceramic supply store. Now I have several shelves and lots of nice long flat dams.

Aside from the fiber paper instead of wash, you may want to baffle a bit. I don't have side elements, so I don't really know anything about it, just I see lots of people with side elements do and also I think watch the alignment of element to shelf. Someone who actually knows might be of more help.

Just want to throw a question out there. Why do people fire so high on a wire melt? When I do mine I go to 1550. Virtually all of the glass is down at 1500. I drop onto 1/8 fiber. I hold it at 1550 for about 20 minutes and take a peak. I currently use 1/2" stainless screen propped up on some fire brick. I have top and side fired brick kilns.

Jeanne, I think that's a good question. I dislike taking any fusible soda-lime glass above 1550, especially for extended periods of time--I suppose it depends, though, on the effect you're after. I think you do get more flow from the glass as it pushes and spreads across the fiber paper--the "boiling" effect.

Morganica wrote:Jeanne, I think that's a good question. I dislike taking any fusible soda-lime glass above 1550, especially for extended periods of time--I suppose it depends, though, on the effect you're after. I think you do get more flow from the glass as it pushes and spreads across the fiber paper--the "boiling" effect.

That׳s my feeling too. The edges of the glass look / 'feel' different


Havi

Jeanne wrote:Just want to throw a question out there. Why do people fire so high on a wire melt? When I do mine I go to 1550. Virtually all of the glass is down at 1500. I drop onto 1/8 fiber. I hold it at 1550 for about 20 minutes and take a peak. I currently use 1/2" stainless screen propped up on some fire brick. I have top and side fired brick kilns.

I have never tried the lower temperature, but it looks like I should. I have been using Laurie Spray's pot melt schedule. Maybe she will give us her thoughts.
Mark Wright

Mark Wright wrote:1685 degrees for 90 minutes.

Mark, we do wire melts at 1625 to 1650 for 15 to 20 minutes (sometimes less) in the same kiln you're using.

Also, we use 6 coats of Bullseye, have had some sticking, but never the kind of trouble you had. The higher the temperature, the more likely you are to get problems with kiln wash. And lots and lots of coats don't seem to work as well as fewer because you have more kiln wash cracking.

I'll just throw out a picture of some recent melts I did. These were done with a top temp of 1550 with a 1/2" stainless screen. I am going to try 3/4" screen and 1" screen to see if it looks different. They did have some pitting in them but when I refired them to full fuse, they pretty much closed up. On the subsequent firing I fired with a 15 minute hold at 1100 then 100 DPH to 1230 with another 15 minute hold to even out the bottom since I blew some nice holes in the pink/green melt when refiring (all refired right on the shelf).

I now don't feel so bad if I make a piece and it doesn't come out the way I had hoped. I just use the glass for a melt.

BTW - the fire bricks in the picture I picked up at the local brick/stone yard. Originally sized 1-1/2" thick by 4" wide by 8-1/4" long. They cost $1.20 each. I sliced most of them in half with my tile saw for great dams.

Have a question. Would it work to use ceramic kiln wash and then top with glass kiln wash? The ceramic can take much hotter heat and should protect your shelves from overruns. Of course I would still use fiber paper. Just something I have been wondering about for a while. Georgia

It might, but if you're also using fiber paper I'm not sure what it would buy you. I'd wonder too if you can apply glass kilnwash over ceramic kilnwash--it might blister, dunno.

In our clay pot melt pots it is more important that all of the glass drains out of the pot then it is for screen melts. If you do not .....the pot can crack due to the difference between the clay coe and the glass coe. If you can be patient I see no problem in lowering the temps and holding longer as long as the pot drains. On screen melt this is not the same problem so I would lower your temp .....if it works it works, right....test test test. The lower the temp the less sticking for sure.
We use 4 coats of fresh Bullseye kiln wash under our melts and "usually" do not have anything stick that a diamond hand pad will not knock off. We never put new kiln wash over old... sanding down the shelves before each firing with a hand sander. We also use stainless steel rings with 1/8" fiber paper lining them to contain the melt and to make a nice form to use.....less grinding and no chance of getting glass flowing off your shelf.

This question of heat (which I totally am with Cynthia and Laurie and others not to go toooo high!) (lower longer has been my motto for years now as I work alot with reactive glass) has always made me think of when we Vitrograph. I am excited about a course with Nathan (an amazing aritst) who is teaching Vitrograph in Calgary at the new studio "PASSION FOR GLASS" . Perhaps my question will be! : how can we get away with pulling cane as I do believe it goes up very very hot, and not perhaps have the same results with melts. (to be able to refire over and over) Just a thought that has stumped me for some time now and look so forward to inquiring of the instructor. Quite a few of the RODS that Bullseye makes are ONLY for flameworking , and perhaps rods are the same concept , in that when you flame work you are creating a continuous strength around the outer edge or almost tension that keeps the beads together and really strong. BUT when you fuse , it flattens out and looses that consistent tension when the rod flattens. I am not explaining this well, but if someone else can enlighten us all, it will help me to choose which colours I would like to Vitrograph that will be super stable. Les