A broken string can be replaced or spliced. When a string breaks at the front termination, such as the agraffe or V bar, its best to replace it.
Piano strings are available from manufacturers, such as Mapes and Roslau in multiple quality grades, plated or unplated. Some makers, such as Stephen Paulello, make strings for historical as well as modern instruments. Pure Sound offers strings made of stainless steel.
Unplated steel strings are the traditional choice for modern pianos. Plated strings don't tarnish, but may not sound as good.
Piano wire is very springy and will pierce skin, even through clothing, if one is not careful. If a string sustains a bend or a kink, it may have false beats when installed. Hence, Piano wire needs to be handled with care, especially during installation.
It is easy to break rusty strings while raising their pitch unless you take certain precautions. When a string is rusty, there are usually tiny bonds of rust holding it to other metal parts such as the pressure bar, upper plate bridge and bridge pins. Rust on treble strings maybe removed through the process of sanding with a sand block.