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  #26  
Old 02-16-2020, 01:16 PM
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Right now, my confidence in the communication between the principals in this are not really working. I do not think the discoloring comes from the glass itself, I do think it's the gas used. I do think the cording issue is widespread and I do think it's not the formula but it is in the processing of the glass. Continuous melt requires serious attention and currently it's not getting it.
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  #27  
Old 02-16-2020, 01:25 PM
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What do you mean by ď Continuous melt requires serious attention and currently it's not getting it.Ē
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Old 02-16-2020, 01:33 PM
Shawn Everette Shawn Everette is offline
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Any viable alternatives to propane and mapp? Don't think there going to let me keep a bottle of hydrogen in the studio. Not that I have a torch that can handle it anyway. I'm not imagining that Martin's using anything that out of the ordinary.

I'm in agreeance with processing being the likely suspect, considering David's able to "melt" the cords away after it's been cooked. Batching issues they should have been able to dial in, but the melt might be a problem of haste for the sake of profit. Though that may have backfired a bit.
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  #29  
Old 02-16-2020, 02:01 PM
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Quote:
Originally Posted by Pringle Teetor View Post
What do you mean by “ Continuous melt requires serious attention and currently it's not getting it.”
****
You can't push a five ton melter or it pushes back in actual calculable ways. When you mix batch, and lets start with the German adage "Well mixed is half melted", so, is it it actually well mixed? I have no idea but the product has serious problems so, I'd start right there or even step back further into the raw materials.

If I could take that mix and put it in a simple pot melter and I could get great glass, I could reasonably say mixing or raw materials were not the problems so that moves us to the melter.

One of the fatal mistakes playing out right now at Cristalica is trying to make a five ton melter melt seven tons a day. Many of you have seen the results of that. Now the furnace which had no maintenance is shot and my understanding is that there's no plan to replace it.

So, let's move to the Czech melter. If we saw that this stuff melted great, and the prototypes suggest that it did but it's not melting great now, one wants to take a look at the process. To make a good glass in one of the beasts involves melting in the hearth and having the melted product go under the bridgewall and out into the forehearth as a glass complete in it's chemical reaction. There' it begins to cool and squeeze with a nice valence shift. Then, out it comes to be sliced and diced on a conveyor, down the line and into whatever receivers are there. You can't speed this up and expect good things to happen. If you are loading seedy glass from the conveyor, you're loading seedy glass into your furnace. But, Speed makes profit as long as no one is complaining. If David can actually torch out cords, speed is an issue but he's remarkably lucky he can do it. Cords in big heavy stuff aren't going to respond to that.
This glass needs to be given the respect glass demands. If manufacturers start treating your primary material like its dogshit, you won't like it and you'll buy something else. To me, boutique cullet is a bizarre venture. Spruce Pine currently is the best deal out there just quietly going along.
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  #30  
Old 02-16-2020, 02:09 PM
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Quote:
Originally Posted by Shawn Everette View Post
Any viable alternatives to propane and mapp? Don't think there going to let me keep a bottle of hydrogen in the studio. .
***
It's an excellent question. I don't know what the EU allows. I do know that the MAPP gases have acetylene in them and that will carbon stuff up.
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  #31  
Old 02-16-2020, 03:53 PM
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Ah. Thank you
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  #32  
Old 02-17-2020, 08:53 AM
Shawn Everette Shawn Everette is offline
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Anybody tried it with natural?
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  #33  
Old 02-17-2020, 10:50 AM
Tom Fuhrman Tom Fuhrman is offline
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Years ago when I was at Penland, Paul Stankard and Dudley were both teaching, They tried a collaboration using the SP from the furnace. The SP turned brown when it was torched and the piece was less than acceptable. That was using a straight propane torch and not an oxy/gas torch that I think would have reduced the problem. If you're planning on using an Exacta torch which is just straight propane you might have to be very cautious or switch to an oxy/gas torch. Just my $.02.
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  #34  
Old 02-17-2020, 11:18 AM
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I believe at that time, SP87 was reacting due to selenium and the quantity was reduced. Possible switched actually to using Erbium instead of the cobalt/ Selenium method. I would think a propane / oxygen unit would work well. Hydrogen is just a risky thing around students since you can't see the flame. The propylene gas that is currently in the MAPP products is largely acetylene which is going to have a lot of carbon.
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  #35  
Old 02-17-2020, 12:47 PM
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Guys - here's notes from a conversation I just had with our tech about how we melt Bomma. Note that we have a 600# Stadelman electric furnace that we run at a working temp of 2150. He's usually doing a large charge once a week and a mid-week small charge. He doesn't wash the Bomma but he does give it a quick inspection and tosses out nuggets that look stoney or have impurities, then tosses it in. Here's what he does:


If 100 or less: we leave the furnace at 2150, toss in a bag (55lbs) distributing the nuggets across the surface of the glass. Waits for the new nuggets to completely melt in until the surface is flat (takes ~20 min), then squirts water at any large bubbles to pop them, wait another 10 min, then tosses in a second bag. Lets it all sit for for 2 hours then squeezes to 2000, then and back up to working temp.

If 400 lbs: We bring the furnace up to 2250. Tosses in a bag (55lbs) distributing the nuggets across the surface of the glass. Waits for the new nuggets to completely melt in until the surface is flat (takes ~20 min), then squirts water at any large bubbles to pop them, wait another 10 min, then tosses in another bag. Continues with this process about every 30 min or so until the charge is complete. (Note that in a 600lb furnace there's a lot of thermal mass, so other furnaces may take a great deal longer for everything to flatten and melt smooth). After the last bag wait 30 min, then a program brings the furnace down to 2150 (our working temp) over about an hour. Furnace holds at 2150 for 2-3 hours. Then squeeze.

The Squeeze: For both melt cycles we squeeze by dropping the furnace to 2000 degrees over 1:45, let the glass sit for 2 hours at 2000, then take 1:30 to return to working temperature (2150) over 1:30.

Hope this helps.
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  #36  
Old 02-17-2020, 01:34 PM
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... and that yields..what? You have indicated you torch out cords. Is the glass actually fined out and relatively issue free? You refer to nuggets that are unacceptable- what issues do they have? Is the original nugget seed free to begin with?
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Old 02-17-2020, 01:46 PM
Shawn Everette Shawn Everette is offline
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Compared to what I'm doing that's a lot of glass and fast. At a maximum I'm charging ~50lbs every 1.5 hours @2100. I'm really waiting for each charge to get a pretty full melt before the next one goes on top. There's still plenty of small bubbles, but everything is a uniform color. You might just be burying cold glass with cold glass only waiting 30 minutes between charges.

The discoloration issue only seems to be a problem when you have the glass at temps higher that you'd usually be using an Exact at, there seems to be no problems with the fluffy.
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  #38  
Old 02-17-2020, 03:03 PM
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I keep asking:
Do the nuggets from the bags have seeds in them or are they fine?
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  #39  
Old 02-17-2020, 03:19 PM
Rick Wilton Rick Wilton is offline
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I have a handful of bomma cullet to experiment with and they are seed free, perfectly clear
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  #40  
Old 02-17-2020, 04:36 PM
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Thank you!

So if the cullet is clean from seeds as limiting as Rick's sample is, then one wants to think about the cords as well as the seeds that follow the charge.
I do thinkI had a terrible time trying to get the seeds out of the cristalica and I had to turn it up into the 2300's to do much good. Ultimately I concluded it wasn't worth that effor but I don't object to the fine materials inherent in batch. I wear a respirator and have for fifty years.

The cords are a different issue and my inclination would be telling the operators at the manufacturing furnace to slow down and see if that improves the product. It actually could be the mixing and raw materials but that can be proved out.
If the cords are in all of the melts in small shops, it suggests the cords are in the actual product.
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  #41  
Old 02-17-2020, 06:25 PM
Shawn Everette Shawn Everette is offline
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I too have yet to experience seeds in the product. I generically think people would have stated from the start that there were seeds in it, given how clean it looks coming out of the bag. Indeed, cristalica and system had runs with significant amount of air present and visible in cold cullet, but no one has stated that as a case so far.

I'm still inclined to believe that the charging method is the primary driver behind seeds, if they are not readily visible in a product this clean. I'll admit that this is somewhat contrary to a singular experience earlier this year when I posted about mystery bubbles appearing as paperweights cooled, but the circumstances are quite different and I could not duplicate the issue from anything else made from that tank.
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  #42  
Old 02-17-2020, 09:39 PM
Bill Worcester Bill Worcester is offline
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Charge the cullet evenly spread.

Using critallica directions we now do not hump the charge in the middle of the crucible, so that it doesnít sink taking bubbles down with it.
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  #43  
Old 02-19-2020, 03:49 PM
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Iím down with the flu and havenít been back to the shop. I thought I posted that the cullet is clear. The only thing I know at this point is that the seeds get better after a few days but never really go away completely.
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