crucible wear

[Greg Gepp]

Hi, my studio is running and things are going well but for some minor tweaking of the annealiong kiln. Can anyone tell me if crucible degradation occurs at the glass/air level any quicker than at any other part, eg above this level or under it ? I'm concerned if I leave my glass in the pot for a day without taking any out, the glass is eating the refractory at this line. If I'm not working on a given day I've been pulling some glass out to lower the level.
Thanks guys.

[Steve Stadelman]

I've only seen this kind of wear over a loooong period of time.

Just turn down to 1850 or 1900 if you leave it stand for a day or two.

[Peter Bowles]

I shouldnt be too worried Greg. The only real time you get significant wear on the pot is when you have raw batch against the side during the melt.
At normal working temps there will be minimal and negligable wear from normal soda lime glasses. What are you melting and what type of pot do you have?

Pete

[Greg Gepp]

Thanks guys, that's reassuring. I'm melting standard Gaffer Batch (not the pelletised one) but not sure of the manufacture of the pot, I got it second hand and it seems fine but for a couple of marks about half way down, there's no leakage that I can tell, but the glass level may be sitting on one of those indents/ holes tonight. I take the furnace down to 1000 deg. C overnight and raise the temp to working temp (1065 deg. C ) before I start making stuff each day, so it's sitting at the lower temp right now.
It wouldn't stress the pot to alternate on a daily cycle between those two temps. would it ?
Thanks for the help,
Greg.

[Peter Bowles]

Hi Greg

1065 sounds pretty damn cool to me, if its working for you at that temp- fine, but sounds very low. As a comparison what temp are you charging and then melting at?

And to be honest, I wouldn't trouble things by running it down to 1000 and then back up again for such short intervals, you will probably find there is no real economy to this. If you are on natural gas and have access to your meter, you can learn heaps by monitoring your usage at idle times, at working times and at melting times. They can vary alot depending on the furnace and with time you can make educated evaluations when its worth turning down, what your glory hole is using. There are some pretty simple calculations to convert the m3 to units and then to dollars spent. mmmm, are you using natural gas? cant remember.

Where did you get the pot?


Pete

[Pete VanderLaan]

Did the pot come from a woman in Sydney? I did sell some EC crucibles down there about two years back or so. I think her name was Michelle.

[TC Robertson]

I always thought the most wear would be in the mid-section of the pot. Our last EC pot lasted 81 melts, then a hole formed near the bottom on melt 82. That was the last one before a rebuild. I just can't let that happen with the much larger pot. Later, TC :(

[Pete VanderLaan]

My opinion is that the void was always there and it eventually got perforated. It takes a long time to go thru them. Some pots have zero voids and may run for 100's of melts. Some don't. Life goes on.

[Brian Gingras]

just pulled my EC pot...about 90 charges on it, looks like someone took a hammer drill to it in spots, other areas are clean and smooth..still see the printing on the side, major erosion where everyone was trailing off over the lip...we have since talked about not trailing off like that :) The pot is also cracked, but thats only because I hit it with a framing hammer to loosen it, and man it took several good hits to make a tiny little crack!

[Brody Shaw]

but Brian, by 'dropping your tails' in the glass, that will speed up the cording of your glass...

[Jordan Kube]

That is just not true Brody.

I'd rather tail off in the pot than have five thousand stringers hanging out the front of my furnace.

[Patrick Kolten]

yes i agree, a tank of glass is a lot less then a new pot

[Greg Gepp]

I'm burning natural gas and keeping constant records of meter readings, and gas usage, and have worked out how to convert to dollars so have an overall idea but will sit down and look a bit closer to assess if the off times are worth turning down.
I have no idea where the pot came from and can't track the previous owner. I do know it's older than two years though.
I have a friend who melted for three years in the same pot, that's gotta be more than 81/90 melts ! not sure which manufacturer that was but could find out if someone wants to know.
Temperatures obviously depend on where your pyrometer sits, and maybe I work a bit cold but I'm still tuning the set up and getting used to blowing again, I last charged 1170 deg C ( for about 8 hours ) but intend to raise that next fill as I got quite a few snots in the glass this time.
As for trails I always have and will continue to trail off into the pot, I want the least glass possible ending up on the floor of the furnace or on the sill.
Thanks for all the help guys.
Greg.

[Peter Bowles]

Greg

We are working between 1120 -1130 depending on what we are making, fill at 1200 and melt at 1240 so it sounds as if you are in the right range. Like you say could be tc placement or could be the polarity of your somp wire ass backwards - doesnt really matter to what numbers you have.

Be sure to check with your gas supplier best rates, we have just signed a new contract for three more years that will deliver gas at a fixed cost and greatly dicounted from standard tariff, and even with the global energy thing as it is , our new contract will have more savings this time than last so I'm pretty happy.

We are just coming up to 160 melts and the pot is just fine, with no impact on the quality of the glass - and we need good glass for almost everything we make. With a bit of care they can last a good while.

Pete

[George Tessman]

we finally got a hole at about 250 melts on my 150# free standing pot, About half way down, so i was still using it to finish up orders now i am going to make some small batches of color while i finish my other furnace. then new pot for this one. In the grand scheme of it all it only cost me about 2 bucks a batch. I think this pot was an EC from Illinois

[Pete VanderLaan]

Originally posted by Brian Gingras
man it took several good hits to make a tiny little crack!
**********************
That's usually not true. I find that EC pots arte very easy to crack with hammers. When I pull a pot, I turn the furnace way up and gently pry the pot loose. Then I shut the furnace off, wait fifteen minutes and then pry again. It will come out very easily this way.

The coarse grain nature of the pots which makes them so great with thermal shock makes it harder to cast a totally void free pot. More no free lunch.

[Brody Shaw]

I'd rather tail off in the pot than have five thousand stringers hanging out the front of my furnace.

you don't clean up your shop???
or 5k worth of gathers on a shift?

from my experience if you keep tailing off in there you will add to the cording process......
and snot up the glass with 'gathering bubbles'


so do you drip in there jordan and not get any bubbles?
by bubbles I mean gathering bubbles....

also no matter how anal you are about cleaning out your pot, your charging procedure, your melt, whatever.....you are going to get cords towards the bottom of your pot....there is no way around this....it anyone says otherwise, I'll call you on it now....
so if your gonna tail off on there, its gonna cord up sooner.....

what kind off stuff you make also matters....you can hide some subtle cording on things........somethings take absolutley pristine glass......

[Kenny Pieper]

Brody I think you can avoid gathering bubbles by staying close to the surface of the glass as you trail off. The bubbles come from the tail flip floping back and forth on top of each other. Trailing off should not cause cording by itsself.

[Jordan Kube]

Making sloppy gathers isn't gonna prevent cords. Cords are not caused by hot glass trailing back into the pot.

Gathering in one spot and trailing off to the right or left depending on which side you gather on can help if you find yourself putting bubbles into the pot when you gather.

[Brian Gingras]

and making sure that your partner knows to not trail off as they come out of the furnace helps...I didn't go over that when I started teaching her to blow...a small detail that made a huge difference. She did dawn the mask and help change out the pot yesterday, so it's all good :)