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Cleaning a Monotype Metal Pot

Started by John Cornelisse, June 07, 2022, 08:53:32 PM

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John Cornelisse

It is far better to take the nozzle off the pump, before you put the piston inside the pump. Than the lead will not have much power to reach the attic.

actually, every time when a casting job is finished, the piston should be removed from the pump, that will remove most lead from the nozzle, thanks the vacuum, when the piston is raised.

After that the nozzle should be taken off. The nozzle can cool down.

Next time before the casting starts... the nozzle should be drilled and cleaned.

Also the oxides that will cover the liquid lead, need to be taken away.


Each year, you need to clean the pot, take the pump out, remove all molten lead, and take away the heating elements, and clean those, and remove all oxide at the walls of the pot.

When this is not done regularly than the oxides will grow around the heating element, and after some time this can be so much that the elements might be overheated.


John, this should likely be a new topic, but I just read your signature note about cleaning the pot. I hate to admit that I've never, ever done this, and I doubt Jim Rimmer did either when he had the Super. I've often wondered how this is done.

I understand that to empty the pot is fairly easy: get it liquid, turn it off, scoop out all of the metal, wait till it cools completely, then remove/clean the elements.

But then what? Once the elements are reinstalled, how do you fill the pot back up? Would you need to melt metal and then pour it into the pot? That makes the most sense.

Also, how does one clean the elements? I'm very hesitant to do anything to them, as I only have one set and do NOT want to damage them, but your note suggests that I'm likely damaging them by doing nothing.

Any feedback/instructions would be very much appreciated.


Keri Szafir

Just pack the pot with the small ingots and fill the empty spaces with old type, turn it on and as the metal melts, replenish it using a regular "pig" (long ingot) later on.

Cleaning is best done with a steel brush after the pot is cooled down. Unscrewing the pump fixture and heater holders on the top of the pot is easier when hot and not always that easy; be sure to use a screwdriver that fully engages the slot. Sometimes a bit of WD40 helps too.
"Any sufficiently advanced technology is indistinguishable from magic." --Arthur C. Clarke
"A thing of beauty is a joy for ever." --John Keats
Founder and owner of Keritech Electronics

John Cornelisse

When I was in America together with Dan Jones, at Richard Hopkins place. We found several machines completely filled with oxides around the heating elements.

One of them needed an hour to melt the pot... It proofed one part of the heaters was not hot at all. Because it could not get rid of the energy... It had burned down.

We could replace the damaged part, but the cleaning needed quite some time. After this I looked through all other machines, all of them had quite some oxide inside...

I cleaned 4 of them before we went back to Dan Jones place...

When the elements are completely covered with oxide it is rather difficult to get it from the elements. And you must be careful too. You do not want to hurt the elements...

When the cleaning is done on a regular basis, at least once a year, it is far more easy to do this job.

John Cornelisse

The linotyper's at this site should also be careful with the heaters in the pot. There is less tin and antimony in the lead, but oxides will grow there also.

Also they should clean the pots on a regular basis.


To clean the elements, do you remove them? Or just try to brush them clean while they're still installed?

Also, steel-bristle or brass-bristle brush to clean them?


John Cornelisse

After taking out the pump and all the liquid metal, lots of oxide can be removed when the pot is still hot.

When the pot is cooled completely, than it is a lot harder to remove all oxide. You might need a screwdriver and an hammer to crush the oxide. Be careful: the heater element should not be touched by this at all.

Remove the screws that hold the heater in place. Under these holders oxide is growing too.

Take the heater-elements out and brush them clean if needed.

After the pot is clean, the machine can be rebuilt.


The elements are probably encased in some steel alloy. Any sort of brass/copper/bronze would contaminate the metal in the pot, and aluminum would be out of the question for any of several reasons. This means they are pretty tough so you could use either a brass or steel brush.

The oxides are often held in place by type metal, so cleaning them off hot might work better, at which point a rag could wipe off most of the deposits. You could heat them with a torch, or just by judiciously applying power to them. You ideally don't want them hot enough to glow though.

Brushing off the oxide will generate a lot or airborne dust, so I would generally be satisfied with removing the larger accretions. The elements don't have to be sparkling clean.

I think you could go a long way cleaning the pot without draining it by using a thin metal strip (a piece of hacksaw blade with the teeth ground off?) to dislodge oxides that have collected between the element and the pot. Another blade with a 90 degree bend in the end about 1cm long could clear the area between the element turns (reaching from inside the pot, don't try pushing this between the pot and element as it might get stuck!). The dislodged oxides should float to the surface, so flux and skim occasionally as you do this to remove the oxides.

Alembic Press

I use an old kitchen knife, to poke down between the elements and the pot wall.

When I had to rebuild one of my composition caster pots a few years ago, to replace all the collapsed asbestos lining, I had to remove the elements, and seem to remember getting the element clamps off was a struggle, as none of the screws would move. I had to drill out most of the screws, same for some of the other screws that held parts on the pot. Luckily I was able to get a friend to retap all the screw holes. And I relined the pot with a non-asbestos lining. All back together and working, but the Funditor bourdon tube is not as accurate as it was, so I may have to replace that with either a spare, or with a solid state controller. Am about to build one such for my super caster, and will see how that performs.

There is always something that needs doing on these machines!

Dan Jones

Here is picture of a clean pot on my Super Caster, that John and I worked on. Sorry, I didn't get a picture of it dirty, however all the elements were covered in oxides. Also oxides collected between the elements and the pot wall, solid. In fact, if you see the cast iron post in the bottom of pot, there was one on the left side that was busted off due to all the crud. When the element heated up, it expanded and actually broke the cast iron boss off. I was lucky not to loose the element.

Note we had to bend the tabs to get the elements out, later, we managed to loosen the screws, not an easy job. I recommend taking the elements out, they clean up without much trouble.

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