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Old 01-07-2019, 03:56 PM
Mark Rendulic Mark Rendulic is offline
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Cleaning out the pot

I am new to running my own shop and I could use some advice. I have heard that you should empty your pot before recharging to clean our any stones or cords that form. Is this something that you should do every time you recharge, or perhaps once a month or so. I cleaned it out for the first time over the weekend and I just gathered it out with a large punty rod and let it drip into a large bucket of water. It worked out okay, but I was just curious about the frequency. Um... Lets just say that it is going to dictate how much cullet I put back in.
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Old 01-07-2019, 08:51 PM
Ron Mynatt Ron Mynatt is offline
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I just work my 300 lb furnace down to 2-3 inch from the bottom each time I charge .That is still a good size puddle in the bottom but it does help keep cords and such from developing.
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Old 01-08-2019, 09:08 AM
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Pete VanderLaan Pete VanderLaan is offline
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Leave the heel in the pot. Once you can't get good glass, it's time to recharge. That poses an interesting question, being at what point do you no longer get good glass and then defining good glass by itself. Glass exposed to the wall of the pot interacts with it making a new glass in and of itself. That causes cords. If it's happening above the halfway point, the pot may be saying "Replace me" but people seem to be pretty cheap on that. So, what can you live with.

The only time you really have to have the pot clean is if you're shutting it off. At that point, get it all out of there. When you are cleaning it out, don't fall into a trap just leaving the door open and have the furnace plunging in temperature. That can unintentionally introduce thermal shock . P{ot's don't perform well after shutdowns and nominally lose about 35% of their projected life, which in my book is 70-90 charge cycles ( less 35%)

Don't shock the pot by adding too much glass at a time either. You don't say what you're melting.
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Old 01-08-2019, 11:39 AM
Mark Rendulic Mark Rendulic is offline
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It's a Denver wire melter so I am melting Cristalica. I am also adding in the clear from the crack-off barrel. So far the glass has been fine, but I don't want to compromise the pot because it is invested and looks like a bugger to replace.
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Old 01-08-2019, 12:21 PM
Eben Horton Eben Horton is offline
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youcan have as much glass as you want in there when you want to charge. I only add enough batch to make a mountain in the center of the pot that just touches the sides of the pot. When that melts flat, I give it a stir and add another mountain. For my 350 lb pot that equates to about 50 pounds at a time or 1 bag of SP87.

Never rush the charge. Stirring is important. I try to stir to bring the lower glass to the top.

Be gentle and patient. Generally the longer I take, the better the glass quality.
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Old 01-08-2019, 12:23 PM
Eben Horton Eben Horton is offline
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Preheating your cullet in a bunch of bread pans would help that Denver out a lot as well. Use your annealer.
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Old 01-08-2019, 01:58 PM
Charles Friedman Charles Friedman is offline
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Always have some casting molds ready to go and dump your clean-out glass into a $$ making project.
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Old 01-08-2019, 06:10 PM
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I can't say enough good things about stirring. I use a potato being very old school. Go to the floor, wear eye protection.
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Old 01-08-2019, 07:29 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Yes the first year I was running a furnace 32 years ago I was having issues not getting good glass, and had heard of stirring with potatoes... not very high tech in my book, compressed air had t be better eh? I made a handle with a valve that would fit on a pipe, stainless no less.
I plunged the pipe to the bottom of the tank and gave it about 4 seconds of wide open air,- first nothing happened, then the whole glass surface of the tank started lifting and rapidly expanded into a huge bubble of the entire tank content, and when it reached 20 “ or so in diameter it self destructed in a spectacular manner, exploding all over the inside of the furnace. I threw myself back in shock and total disbelief, holding 18” of pipe tube... the pipe had completely oxidized off, in seconds. I lived with nickel green glass for a while, I never attempted another stir after that.
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Old 01-08-2019, 08:11 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Mark,
As to your question, I don't think you need to worry about emptying your pot, work it down when you can but if you notice cords or whatever use a ladle to empty it. Don't mix your own shards with the Cristallica, save it and melt itall at one time, like when you're going to turn off soon. Don't dump ladeled or gathered glass in water, it makes cracks that will make bubbles when you melt it,
Just lay it on your own shards and let it cool
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Old 01-08-2019, 08:42 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Eben
No,no the objective in most of the world is to have good glass the next day, its only in the US that some strains of the studio glass movement thinks that melting is done very cold and slow and glory holes should be under powered and cold
This in spite of otherwise being well known in Seattle

Last edited by Michael Ahlefeldt-Laurvig; 01-08-2019 at 08:45 PM.
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Old 01-08-2019, 10:07 PM
Eben Horton Eben Horton is offline
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Quote:
Originally Posted by Michael Ahlefeldt-Laurvig View Post
Eben
No,no the objective in most of the world is to have good glass the next day, its only in the US that some strains of the studio glass movement thinks that melting is done very cold and slow and glory holes should be under powered and cold
This in spite of otherwise being well known in Seattle
I have perfect glass the next day. Slow and patient does not imply cold.

I have a charging program that I run at 6:00 pm the day before I charge. When I come in at 8:30 the next morning the furnace is sitting at 2300 waiting for me. I throw in a little at a time and never throw in any batch until the previous batch is melted flat. I usually am done around 7 pm. The furnace goes up to 2325 for 4 hours if I remember right and then drops to 1900 where I find it the next morning.
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Old 01-08-2019, 10:14 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Well a lot of meltcycles suggest over a day
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Old 01-09-2019, 08:47 AM
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Pete VanderLaan Pete VanderLaan is offline
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Potato gives reasonable control over the gas volume released. I won't use compressed air, viewing it as dangerous. The temperature of the glass matters as well. Hotter glass is far less viscous and stirs easily.

The Germans ( bless their toxic little heads) did it with a lump of arsenic in a wet cloth. That I won't do.
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Old 01-09-2019, 09:06 AM
Josh Bernbaum Josh Bernbaum is offline
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I always use a potato 1/2 hr. before I turn down from high fire after melt cycle.
I think it's a good habit, it can't hurt if done right, can only help to homogenize things. I think it's maybe even more helpful for color melts but I do it on all clear melts too. I don't stir between charges (unless for some color melts), seems to work best after a long soak at high fire when the glass is at a lower viscosity.
I, as well, try not to pull the heel out if I don't have to. I also think Russet Potato works best..
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Old 01-09-2019, 01:14 PM
Mark Rendulic Mark Rendulic is offline
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Thanks for all the great info! I've heard about the potato, but never tried it. I think that is a better choice than arsenic! I also think that preheating the cullet will make a big difference.
Thanks to everybody who shared!
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Old 01-09-2019, 03:33 PM
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Scott Novota Scott Novota is online now
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Apple works well also. Just depends if you want it to smell like a apple pie or a fresh batch of French fries. I used a granny smith last time and was seriously temped to taste it but some part of my brain vetoed it.
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Old 01-09-2019, 04:47 PM
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drill a hole in the potato a touch smaller than the punty which you will never want to use for anything else since it's going to get bent. Wear the goggles. You really won't want to lose the potato in the pot. Physically hold it against the walls and the floor, moving it around. 35 -30 seconds should do it. Do it hot.
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