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Antique Cast Iron pot repair.


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Just to get some advice.

I have an antique cast iron pot, about two gallons, with feet in a hemispherical shape that has a crack from the pour spout down to near the bottom.

For many years my mother used it as a flower pot holder and refused to let me play at fixing it. Now, with it kicking around the floor and not part of my decorating scheme I'm wondering what the best way of fixing it will be.

The metal is quite thin, on the order of 1/8 thick. This is not one of the Lodge cast iron pots.

I'm wondering what the best way is to mend it. The crack is roughly 1/32 wide at the top and tapers down. It takes a litte pulling to spring it back together.

I'm afraid that my stick welder will just melt it to puddle. I've never seen any mig wire for cast iron. I could silver braze, or bronze braze.

I've never tried to gas weld cast Iron. My first thought was TIG but that equipment is not available to me.

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This is a tough one Charlotte. What makes it so difficult is mostly the circular shape. What ever method you use, tig or torch brazing, stick or torch with cast iron rod, you will face the same problem. Imagine your piece was a flat bar, broken in half. You heat it, weld it, whatever, and it expands whatever amount it needs to as a result of that heat. Now take the same flat bar and form it into a circle. Heat it at one spot(weld, braze, whatever, the iron expands from the heat, only it is restrained by itself, and being brittle and non maleable, it just breaks somewhere else.
Not that it can't be done, I just want you to understand the forces or problems you are dealing with.
The solution is pre-heat, post heat, slow cooling. Since you mentioned methods of repair which would not be good color matches, I asume you will paint it. The best repair would be square cast iron rods and torch welding, but also the most difficult and not needed since you are not worried about color match. Just so you know, 7018 stick and 70 series mig wire will also weld cast iron and give good color match. You already eliminated Nickel stick repair, with your asumption that the metal is too thick. This leaves tig-brazing(equipment not available) and finaly torch brazing.
To start, find the terminus of the crack. Drill a small hole at the very end of the crack, between a 1/16 and an 1/8" diameter. Find a way to heat the pot. A charcoal grill would do nicely. If there were no other method, a wood fire on the ground wood work. Clean the joint with a wire brush. Vee it just a little bit, just from the outside. Close the crack using several turns of bailing wire if possible. The wire will need to remain untill the repair is complete, so don't run it where you will be brazing. Heat the pot to a black heat or thereabouts. Have an area ready to work, consisting of either enough fire bricks to support the pot, or if nothing else, a bed of DRY sand. Once the pot is sufficiently and uniformly warmed, remove to you prepared work area. Perform your repair, all the while playing your torch over the rest of the pot ocasionaly to maintain temp. Upon completion of repair, return to heat source and allow to get evenly good and hot, but not so hot as too melt your brass. Bury in dry ashes, or dry sand, allow to cool . If you have to, you can wrap with fiberglass insulation, but the glass will burn some and doesn't smell good at all. Good luck. If you master the art of repairing cast iron, you may find a good source of work at antique shops.

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Thank you all for the advice. Arftist, thank you in particuliar for your detailed process notes.
It would be great aslo if Dragaon's Lair could come up with a company that has cast mig wire.

I really like this pot because it's clean precise casting and excellent surface finish is such a contrast to contemporary reproductions.

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Charlotte if you are not planning on using it I would leave it alone and use it as a "conversation piece". I have seen a few cast iron pots that have been "repaired" and they lost their beauty and were not functional and one had a bigger crack about 1/2" from the one welded. If you want a cosmetic repair I agree with quenchcrack and use JB weld with enought soot to make it black then fill in the hole.
Just my 2 cents worth
William (PS Yes I do know about castiron pots I won state championship dutch oven cook off twice)

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