While trying to loosen the stuck 3rd slide of a BACH Bb trumpet, the Berlin musician broke two braces. This connections are hard soldered and normally very resistant. So here was a little more force involved :-)
In this case, the broken braces consist of several individual parts (two brace plates made of sheet brass and a turned part). To repair the defective solder joints, all components had to be removed from the slide, cleaned and refurbished. Afterwards everything could be soldered again. Here, it is important to work very precisely, otherwise the braces might not fit into the slide later on. After hard soldering¹, the components covered with scale and oxide are cleaned in pickle and pre-polished on the buffing machine. Now the slide could be soft soldered together again. The entire 3rd slide got a new silver plating after the final high gloss polishing. In the end, everything looks like NEW again!
¹ The difference between soft and hard soldering is defined by the so-called liquidus temperature (melting temperature) of the solders. If the liquidus temperature is below 450°C, it is soft soldering; if the liquidus temperature is above 450°C, it is hard soldering. Soft-soldered joints can be quickly and easily removed by the brass instrument maker (e.g. as part of a repair). A hard-soldered joint is significantly more stable and is used in instrument making for assemblies that are to be permanently joined together.