Soft Solder Problem

[mikemill]

I was attempting to solder a piece of sheet brass around a brass form, I tinned the sheet but I found the sheet difficult to follow the form so I then annealed the brass sheet. During the heating process the solder ran to form blobs I then tried to scrape off the solder but found it was very hard, then started to file the solder ( which I would normally not do) the solder was as hard as steel.
I have not encountered this situation before, could it be the lead in the solder had been burnt off thus leaving just tin? Anyone got a thought on what happened.

Mike

[old-and-broken]

It probably picked up some zinc from the brass and transformed into a lead/tin + zinc alloy.  I believe the tin + zinc + a little of the copper can make a bronze type alloy.  Most of them very hard.

[Alan Haisley]

This may be a "do over". Try again, but anneal and shape the sheet as best you can before tinning it.