Tin-lead (Sn-Pb) solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile and shear strengths. Lead mitigates the formation of tin whiskers, though the precise mechanism for this is unknown. Today, many techniques are used to minimise the problem, including changes to the annealing process (heating and cooling), the addition of elements like copper and nickel, and the application of conformal coatings. Alloys commonly used for electrical soldering are 60/40 Sn-Pb, which melts at 188 °C (370 °F), and 63/37 Sn-Pb used principally in electrical/electronic work.