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I have a Mk1 rear quarterlight frame that has a split/crack on each side of the frame where it rises to meet the lower edge of the piano hinge
A mate has had a go at TIG welding it.
Its unmarked ie no sign of rust and a magnet doesn't touch it so I made the assumption that it is stainless.
However when he TIGS it as it heats up it turns blue and spits back.
My question is : Is it made from a different material other than stainless or is it stainless with a chrome coating? It may possibly be a 59/60 frame (which had a different catch on it) but usually MK1 frames have pitted or fallen apart by now so this has me flummoxed.
Cheers. Mark

It's brass - when you try and TIG brass it burns the zinc content off which causes the spitting

No way Gordon . I never thought they were made of brass. Thanks for sharing.
Were some made of brass and others of something else?? Usually Mk1 frames go all black and pitted like Mazak

You can get stainless ones, but not sure what they were fitted to - may have been european builds. Doc used them in his broadspeed build

Mazak is a zinc alloy, brass is an alloy of copper with 33% zinc.

Had a chat with about chrome plating with my pet plater - one of his comments was that chrome will (slowly) react with copper and zinc which is why it pits over a period of time. Nickel is a better base layer. The reason why copper is used as a base layer is that it is cheaper and you can quickly build up a thick layer to hide imperfections