fast fire 20mm

[Bert Weiss]

I am not quite unpacked from my 3 week journey teaching and consulting. I probably learned as much as I taught.

Last week, I worked with a company that bought a Moretti fuser/slumper and needed some guidance on what to do with it. The company owner had been to Italy and been given a workshop on using it.

I decided to use the Moretti firing schedules. They were at least twice as fast as Graham's. My notes are still in my suitcase, in my van, out in the yard. I'll get to them by tomorrow or Monday. (I'm whooped). I started a fuse firing including an hour squeeze at 1240ºF at 4:30 one afternoon and I had the glass out of the kiln by 2 or 2:30 the next day. The kiln had 3 pieces: 27" diameter, 27" x 36" (both 2 layers of 10mm) and a piece 30" x 42" x 20mm (3/4").

Normally I would use a sechedule that takes me somewhere between 36 and 48 hours, up and down.

By the time I left that afternoon at 5 everything was in one piece. I looked at the edges and corners with a polarizing filter and saw nothing out of the ordinary. No fuzz at all really.

I advised them to slow down for the slump firings. I can't wait to hear how that goes.

So here's the question: Can I expect to see stress showing up on the corners or edges when looking through the darkened polarized filters?

We used a fast Moretti schedule the day before while kiln carving some 10mm (faster than the 20mm one). I also saw no stress and we cut one sample piece to see how it cut, and it cut just fine.

I have always known that industry goes faster than we art folks. I didn't think that twice as fast would work so well.

The Moretti kiln had a strange set up to me. It was one zone. Under 700 watts per cubic foot, I think. The thermocouple was set in the very upper corner of the bell, a couple of inches from a quartz tubed element. I found this hard to understand so I used their annealing instructions instead of mine. They did a fast rampdown starting around 1075ºF for float glass. This is a temp above what Graham or I would have chosen. I am assuming that the thermocouple is reading a temp well above the glass itself.

Does anybody have any comments about quick annealing. I can testify that the fast heatup worked, that's easy. The fast anneal is a somewhat grayer area. We are dealing with uniform thickness glass, more or less. There are some small bubbles around the fused pieces, nice though.

I used some sandblast stuff that they had in stock to sand cast kiln carve with. It worked very well. We used plaster of paris, diatomaceous earth, and some pricey Bohle seperators, along with the sand.

[rosanna gusler]

wow bert, what a trip! i bet it felt good to sleep in your own bed. it seems to me if the stress was there you would see it. the light either is bent or it is not. moretti must have done extensive testing with lots of extra thermocouples to come up with their 1 zone/1 measurement set up. lots of room for potential error there i think. especially since they seem to be pushing the envelope. how about when the one thermocouple ages? how about when the elements or their connections age? the scheduals seem to assume a constant relationship between what is happening 'on the floor' and what is being measured 'in the corner'. i think that with a machine of that size, more is better in terms on sensing and controll. wow i think alot. lol. might be time to do some how fast can 'I' go test firings in your set up. it must have been great to play with an out of the box new kiln made by someone else. lots of new what ifs? or yea i was rights? rosanna

[Bert Weiss]

wow bert, what a trip! i bet it felt good to sleep in your own bed. it seems to me if the stress was there you would see it. the light either is bent or it is not. moretti must have done extensive testing with lots of extra thermocouples to come up with their 1 zone/1 measurement set up. lots of room for potential error there i think. especially since they seem to be pushing the envelope. how about when the one thermocouple ages? how about when the elements or their connections age? the scheduals seem to assume a constant relationship between what is happening 'on the floor' and what is being measured 'in the corner'. i think that with a machine of that size, more is better in terms on sensing and controll. wow i think alot. lol. might be time to do some how fast can 'I' go test firings in your set up. it must have been great to play with an out of the box new kiln made by someone else. lots of new what ifs? or yea i was rights? rosanna

Yeah

[Brian and Jenny Blanthorn]

I am not quite unpacked from my 3 week journey teaching and consulting. I probably learned as much as I taught.

Last week, I worked with a company that bought a Moretti fuser/slumper and needed some guidance on what to do with it. The company owner had been to Italy and been given a workshop on using it.

I decided to use the Moretti firing schedules. They were at least twice as fast as Graham's. My notes are still in my suitcase, in my van, out in the yard. I'll get to them by tomorrow or Monday. (I'm whooped). I started a fuse firing including an hour squeeze at 1240ºF at 4:30 one afternoon and I had the glass out of the kiln by 2 or 2:30 the next day. The kiln had 3 pieces: 27" diameter, 27" x 36" (both 2 layers of 10mm) and a piece 30" x 42" x 20mm (3/4").

Normally I would use a sechedule that takes me somewhere between 36 and 48 hours, up and down.

By the time I left that afternoon at 5 everything was in one piece. I looked at the edges and corners with a polarizing filter and saw nothing out of the ordinary. No fuzz at all really.

I advised them to slow down for the slump firings. I can't wait to hear how that goes.

So here's the question: Can I expect to see stress showing up on the corners or edges when looking through the darkened polarized filters?

We used a fast Moretti schedule the day before while kiln carving some 10mm (faster than the 20mm one). I also saw no stress and we cut one sample piece to see how it cut, and it cut just fine.

I have always known that industry goes faster than we art folks. I didn't think that twice as fast would work so well.

The Moretti kiln had a strange set up to me. It was one zone. Under 700 watts per cubic foot, I think. The thermocouple was set in the very upper corner of the bell, a couple of inches from a quartz tubed element. I found this hard to understand so I used their annealing instructions instead of mine. They did a fast rampdown starting around 1075ºF for float glass. This is a temp above what Graham or I would have chosen. I am assuming that the thermocouple is reading a temp well above the glass itself.

Does anybody have any comments about quick annealing. I can testify that the fast heatup worked, that's easy. The fast anneal is a somewhat grayer area. We are dealing with uniform thickness glass, more or less. There are some small bubbles around the fused pieces, nice though.

I used some sandblast stuff that they had in stock to sand cast kiln carve with. It worked very well. We used plaster of paris, diatomaceous earth, and some pricey Bohle seperators, along with the sand.

Yo Bert

Hope U get paid a lot as consultant

All those years of slaving 2 just give that critical bit away

When I went 2 Pilkington's I was watching the float glass comming out realy fast

A fast walking pace

So cant have been cooling long

Cant have been out of the tank more than say 5 - 10 mins

I think its all about evenivity



In ur firing

The high aneal I guess is 2 achive evenivity B4 the aneal cycle

Having said that

Start putting colour in n fuzing withy uneven bits n U gotta take care

I think Grahams schedules do err on the very cautios side

Nothing wrong with that but with knowledge I think in the most part U could speed up a lot

C what the manufacturer of the glass says about aneal ????

Brian

[Bert Weiss]

Yo Bert

Hope U get paid a lot as consultant

All those years of slaving 2 just give that critical bit away

When I went 2 Pilkington's I was watching the float glass comming out realy fast

A fast walking pace

So cant have been cooling long

Cant have been out of the tank more than say 5 - 10 mins

I think its all about evenivity



In ur firing

The high aneal I guess is 2 achive evenivity B4 the aneal cycle

Having said that

Start putting colour in n fuzing withy uneven bits n U gotta take care

I think Grahams schedules do err on the very cautios side

Nothing wrong with that but with knowledge I think in the most part U could speed up a lot

C what the manufacturer of the glass says about aneal ????

Brian

Consulting and teaching can pay the bills without running up the electric bill, so there is actually profit at the end of the month. The art thing seems to eat up the "profit" back in to expenses. Besides I learned at least as much as I gave away.

I agree about evenivity. Annealing takes place in a matter of moments. It's during the moment that evenivity is achieved.

[jerry flanary]

I believe that holding on the high end of the annealling range allows the stress to be relieved faster, theoretically you could get out all the stress during the high hold, then the rampdown just has to be slow enough to not introduce more stress than is acceptable.

On experimenting on "how fast you can go" If you finally go so fast that you get stress that bothers you just re-anneal. Unless it cracks...

I suspect moretti is a lot more forgiving than say BE but thats just a guess.
j.

[Bert Weiss]

I believe that holding on the high end of the annealling range allows the stress to be relieved faster, theoretically you could get out all the stress during the high hold, then the rampdown just has to be slow enough to not introduce more stress than is acceptable.

On experimenting on "how fast you can go" If you finally go so fast that you get stress that bothers you just re-anneal. Unless it cracks...

I suspect moretti is a lot more forgiving than say BE but thats just a guess.
j.

Jerry

My understanding is to the contrary. Annealing gets done faster at the correct lower temperature. This was confirmed for me by Dan Schwoerer and Ray Alghren. This is why you do a slump test to determine your anneal soak temp.

The problem with the Morretti kiln setup is that the thermocouple is in a very innaccurate place relative to the glass, so a ramp is needed to get the job done.

I am using float glass, not Morretti. It is more forgiving than BE, because it is one color and uniform thickness.

[Jerry Barnett]

I suspect moretti is a lot more forgiving than say BE but thats just a guess.
j.

A lower COE glass is less susceptible to thermal shock and can be annealed faster than a higher COE glass. A 90 COE glass will be more forgiving than a 96 or 104 COE glass, but not as forgiving as float glass.

Bert, is the height of the bell much shorter than usual for a bell kiln, forcing a high thermocouple position? Also curious about the arrangement of the elements in the roof.

(From the thread title, I first thought you were posting about some type of automatic weapon of possible interest to those truly fed up with stupid questions from the public.)

Jerry

[jerry flanary]

A lower COE glass is less susceptible to thermal shock and can be annealed faster than a higher COE glass. A 90 COE glass will be more forgiving than a 96 or 104 COE glass, but not as forgiving as float glass. Well this is certainly true about thermal shock and COE just look at any borosilicate vs soda but my point was about Moretti being forgiving. I am just guessing but I think Moretti uses a bunch o lead to get all their wacky colors to fit. and lead can make things more forgiving. Anybody on the board know the average lead content for Moretti?

My understanding is to the contrary. Annealing gets done faster at the correct lower temperature. This was confirmed for me by Dan Schwoerer and Ray Alghren. This is why you do a slump test to determine your anneal soak temp.
Im sure those guys at BE know their stuff but according to Pete Vanderlaan:If I understand this correctly: Annealing is something that occurs in a fixed range wherin strain is relaxed in the piece. The range is from the softening point down to the strain point. Below the strain point, no further annealing can occur. Annealing at the softening point is counter productive because of deformation, so a point below the softening point is chosen. The closer to the softening point, the faster the annealing will occur. The closer to the strain point the slower the annealing will occur.

If a piece is put into an annealer below strain point and has to be brought up to anneal it, it will take thirty times longer to anneal the piece then it would if it had been put in above Strain Point. It can be taken up to the upper annealing point to speed the process along. ( Frank Wooley 2001- Corning) There is little to be said for annealing near the strain point.

I hope this clears up some of what I said earlier, I was just trying to use some of my meager experiences to help theorize about why their schedule flew. Sorry that I missed the part about float glass in the original post.

So here's the question: Can I expect to see stress showing up on the corners or edges when looking through the darkened polarized filters?
Bert, does stress ever show up later with a polariscope if it is not there at the beginning? Not being a smartass just want to know if you have experienced this. You said that you already checked it out w/ polarized lenses and it looked good. Have you ever had stress just appear later?
j.

[Bert Weiss]

Jerry

Pete's statement is consistent with my understanding.

Lundstrom said to do a slump test, which determines the softening point, and do an anneal soak 100ºF below that point. For me the softening point of float was at 1100ºF, so I soak at 1000, and ramp using the same time as my soak to 900. Graham does a short soak at 1030 and a long ramp down to 940. I take the same time to get from 1000 to 900 as Graham takes to get from 1030 to 940. We are spending our time at different points.

The Moretti schedule for 20mm float glass is in centigrade: 0>300- 2 hours and 15 minutes. 300>520-2 hours. 520>580 35 minutes. Then do your thing up to temp and then to anneal, 580>520-2 hours 520>300-2 hours. (you ºper hour rate folks will have to calculate that in order to understand)

I have seen the evidence of stress as white fuzz in the polarizing filters, but saw none on the glass fired at that schedule.

The elements were coils wound inside quartz tubes. The theromcouple was at the same height as the elements and only a couple of inches away. I think the bell was about 18" deep.

[Jerry Barnett]

I would agree with Pete's statement if the sentence "The closer to the softening point, the faster the annealing will occur" was "The closer to the annealing point, the faster the annealing will occur" instead.

Addition of lead to glass makes it more "forgiving" of expansion mismatches, so there may be lead added to some Moretti glass to try to lower its strain point enough to keep it compatible with other Moretti glass.

Jerry

[Bert Weiss]

I would agree with Pete's statement if the sentence "The closer to the softening point, the faster the annealing will occur" was "The closer to the annealing point, the faster the annealing will occur" instead.

Addition of lead to glass makes it more "forgiving" of expansion mismatches, so there may be lead added to some Moretti glass to try to lower its strain point enough to keep it compatible with other Moretti glass.

Jerry

Jerry

Morretti made the kiln. Guardian made the float glass, no lead.

[jerry flanary]

Bert, is this Moretti kiln made by the Moretti company or is it just yet another Moretti company like Moretti beer? I had made my comments about moretti glass because I assumed that their fast schedules were designed for moretti glass. Is this the company:
http://www.morettiforni.com/ceramic2.htm
Was it like the FVE / 1-2?

Also have you guys worked at all with the effetre glass?

And about the polariscope, have you ever seen stress appear a few days later in a piece that previously read good? I am really curious about this.
j.