How to Body Solder

Body soldering replaces synthetic filling when fixing autobody panels.

Body soldering is another term for lead loading. The process is necessary when you want to fill a drilled dent removal hole or other perforation using lead, as opposed to a synthetic body filler. Although lead filling body panel holes requires more skill that spreading resin-based filler and sanding, the result is less likely to absorb moisture and more likely to last longer.

Things You'll Need

• Lead soldering stick
• Flux
• Lubricating oil
• Propane torch
• Wooden lead spreader
• 60 grit sandpaper
• 100 grit sandpaper
• Water
• Clean cloths

Instructions

1. Sand the area completely, attempting to remove as much loose rust and contamination as possible.

2. Activate your propane torch. Heat the area to the level needed to apply the flux without it bubbling. Practice is required with each type of surface to understand what duration is required to achieve this perfect heating level.

3. Apply a liberal amount of flux using the applicator brush inside the container. You have the right amount of flux if it neither bubbles nor turns bright silver. Look for the flux to be a dull grey color.

4. Break off a piece of the lead stick by twisting. Stick the lead to the application spot. The proper amount of heat and flux with allow the lead to stick on its own.

5. Soak the head of the wooden applicator in the household oil to prevent the lead from sticking. Heat the lead applied to the metal until it changes to a shiny color. Immediately press the lead evenly into the hole or deformity with the applicator.

6. Allow the applied lead to cool. Sand off excess lead by hand with 60, then 100 grit sandpaper.

7. Completely clean the area with water and cloths to remove excess flux. Re-apply the lead filler as needed to fill the spot to your satisfaction.

Tips & Warnings

• If in doubt, apply more lead than you think you need. You can always sand off excess, which takes less time than applying more and doing the process over again.

References

• Tommy Sandham: Lead Loading or Body Soldering
• Frost Auto Restoration: How Do I Load Lead?