Traditional lead-based body solders have been the choice of restorers and custom vehicle builders for over 80 years. Lead 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. Frost body solder kits use bars consisting of 30% tin and 70% lead, which give the widest spreadable temperature range.
This mix produces a solder that is easily applied to vertical and horizontal surfaces with a long spreadable working range. Tensile strength is 6140 psi which refers to the amount of force required to pull a substance apart (In this case if we have a soldered joint that covers exactly one square inch, it would take 6140 lbs to pull it apart). Body solders containing lead must be levelled by filing -- never sand lead-based body solder because sanding puts toxic lead dust in the air. Furthermore, grit from the sand paper may embed in the solder and cause corrosion.
The lead-based Solder is easier to use
The low melting temperature makes the 30/70 lead-based solder slightly easier to use than our lead-free solder.
Lead-Free Body Solder is suitable for powder coating
With a better Tensile Strength (greater than 9000 psi), the lead-free solder is more appropriate for building up door and other panel edges, and style lines. Levelling can be done by filing and sanding since no lead particles will be dispersed (Be sure to wear an appropriate dust mask as for any metal grinding operation). This is one of the few solders that can actually be powder coated and cured at 200°C (with accurate temperature control) without deforming. The fact that the lead free can withstand powder coating temperatures is a big benefit.
Different Paddle Uses
In the case of the lead-based solder the paddle is used like a knife spreading butter.
In the case of the lead-free solder the paddle is used to push the solder into the surface. The "spreading" technique is not recommended in the case of the lead-free because impurities may become trapped
See the similarities between Lead and Lead-free Body Solders, click here...
Lead-based versus Lead-Free Body Solders , click here...