Cleaning the Melting Pot

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  • Last Post 04 June 2016
Eutectic posted this 03 June 2016

Lead melting pots require cleaning, and this is especially true of bottom pour pots. The alloy components oxidize and the small particles of oxide aggregate and adhere to any surface. This dross coating builds up on the walls of the pot and on the valve components, and slowly clogs the nozzle. The dross forms an insulating layer and this means that the heating element has to run hotter and longer. If the thermostat is external to the pot, as it is on most pots, it means that the actual temperature of the alloy at any setting slowly decreases. The cure is to stop and clean the pot. I usually clean my RCBS pot about every 10 hours of casting. This time I was lazy and about twice that,  had elapsed and I was reminded of my sloth when the nozzle started dripping and I was getting lots of reject bullets with dross inclusions.

I drained off most of the alloy and turned the pot upside down while hot to get out the very last drops. I clean with a sharp but blunt tip knife, shaving the walls and scraping the bottom of the pot. Here is a picture of the quarter pound of dross I removed.   Pretty ugly, I waited too long.

Steve

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onondaga posted this 03 June 2016

http://www.castbulletassoc.org/forum/view_user.php?id=6924>Eutectic

They all take cleaning.  A tip I learned to keep the pot cleaner and requiring less often scrape down uses oil.

When I finish a casting session, I empty the pot to ingot and lightly steel brush the hot pot upside down. I soak the pot with WD40 as soon as doing that is not a fire hazard.

The next casting session is a pretty clean start, and it goes on. I don't get the oxides as bad and the usual crud I get is caked beeswax I sometimes use for flux when I do a reduction fluxing. I generally use sawdust for a cleaning flux when casting. When I get Tin oxide casting hot is when I may do a reduction fluxing by fire with beeswax.

Leaving metal in the pot being OK for me doesn't happen very often. I might leave a clean fluxed puddle less than a pound,  and when cooled, I still soak with WD40.

Gary

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Eutectic posted this 03 June 2016

Gary, I do not do a lot of fluxing while casting. The ingots are clean so I just add more and keep going. I have tried sawdust and it does reduce the dross, and pine sawdust smells nice. You do not need to flux unless you are ladle casting. Your idea using WD-40 is good, I used to use it on my LEE pot which was plain steel and rusted. I stopped using it when I got the RCBS which is stainless steel. I try to leave the pot 1/3 full if I am going to continue using that alloy. I can do a partial dross removal at shutdown, but it does not get everything. WD-40 does cut down on the dust, which you must not breathe! I will use it next time and see if it helps. Steve 

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OU812 posted this 03 June 2016

That pot was dirty.

I flux before casting, scraping the insides of pot and stirring well brings junk to the top to be scraped off.

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onondaga posted this 03 June 2016

Eutectic wrote: Gary,   .....I can do a partial dross removal at shutdown, but it does not get everything. WD-40 does cut down on the dust, which you must not breathe! I will use it next time and see if it helps. Steve  It is the upside down wire brushing I mentioned that is the most helpful for me. A danger exists when doing that. The pot is at full running temp and on when I do that. The aluminum base of the Lee bottom pour pot is pretty easy to hang on to, but DON'T SLIP your hand position hanging on to the aluminum. You could get burned. After the brushing, then I shut the pot down and cool some before WD40 application.

Gary

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358156hp posted this 03 June 2016

Hot water does wonders for cleaning out dirty pots, once all of the alloy is removed of course. I hadn't thought about it before, but since I have a PID controlling my pot temps, I could set it just above the boiling point of water, and even use a dab of soap. I'll have to try this. A lot of the scaly stuff that sticks to the pots walls is water soluble, but an annoyance and a hazard to remove by abrasion.

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onondaga posted this 03 June 2016

358156hp wrote: Hot water does wonders for cleaning out dirty pots, once all of the alloy is removed of course. I hadn't thought about it before, but since I have a PID controlling my pot temps, I could set it just above the boiling point of water, and even use a dab of soap. I'll have to try this. A lot of the scaly stuff that sticks to the pots walls is water soluble, but an annoyance and a hazard to remove by abrasion. The corporation I used to work for (Williams Gold Refinery) made a steam gun station for Dental Laboratory use. It was a bench top model, portable and very powerful. That thing is terrific for cleaning bullet casting pots !!!!! However, it is prohibitively expensive for a hobbyist at well over 2 grand. In the Dental Lab it is used for removing flux after welding, brazing, soldering and cleaning casting crucibles. The unit is about suitcase size with a high pressure nozzle pistol and hose.

Gary

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vmwilson posted this 04 June 2016

My method has been changed a bit the last year or so.  I only flux my top pot which I use as a feeder pot for the lower one and I've been happy with NEI's flux up there which is apparently some sort of rosin flakes.  The ingots that go in were at least relatively clean so it doesn't take much flux.  Now if the lower pot needs a little touching up a small dab of beeswax seems to be the ticket and not very often at that.  So far it's working for me. 

My smelt pot gets fluxed with stearine flakes from stuff I acquired at work years back.  Along with generous stirring and scraping of course.

Mike

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