1 Answer

I have used silver solder to make a repair in cast iron. That was to repair a food service piece  too. There are fluxes that should never be consumed  so I use a Hydrogen fueled torch and halo to remove oxygen from the weld. An intelligent welder may know how best to do that considering the difficulty in welding cast iron. My way was how I repaired a cast iron fry-pan. the crack did not break away until i attempted to draw the crack closed by wedging it closed while heating. So then I joined it to a cold tight fit by careful reduction of the touch points. Heated to silver solder i place the first time failed due to the need for silver solder throughout the thickness of the pan to prevent leakage of oils through the crack. So I had to heat it enough to open the join, cool it slowly then clean the crack line to apply a thin coat of solder, using a metal brush(stainless steel) to remove the excess silver solder. The heat both sides evenly, join and cool. The result was lovely ....a nice clean join over the entire crack line and never broke again. Aquire-ing the skill to get the job done and look right took time and the right tools. Persistence can cost lots in silver these days. I'm sure there are better ways that I have not tried and don't know about. I avoid solder fumes these days as I noticed the effects on welders with swollen, arthritic hands.