Lead is the old, traditional method of finishing car bodies, while plastic filler is relatively new to the game (40 or so years!). Unfortunately the art of lead loading has died out to a large extent as everyone reaches for the quick, easy, -- no skill needed -- plastic filler. There is also concern about continued use of lead causing a build-up of toxins in the user's body. However, since we will only be doing a few hours worth of working with lead as against a 30 year career in the panel beating business, I think we are relatively safe.
Advantages of Lead
Lead is waterproof, while plastic filler is not. So if you are working on a car over a long period, you may wish to consider using lead rather than plastic filler. If you plastic fill and leave it without painting it, it will gradually absorb moisture. Priming is not enough. I've spoken to several paint manufacturers who state that primer is NOT waterproof. When you do come to paint you will have potential problems from the moisture content within the filler.
Lead will also "bridge" small holes in the metalwork. By small I mean small, not holes you can get your fingers into…Use some common sense here!
A section of a practice door (see picture above) . The lead repair to the right shows signs of needing more lead, as there are some depressions which have not been filled. The hole at the bottom, left, could be cleaned up, and if the remaining metal is sound, could be "bridged" with lead.
The lead used in lead loading is actually a mixture of lead and tin. The required proportions for motor vehicle work are 70% lead and 30% tin. This sort of lead has a melting point of about 500 degrees F. Remember these proportions, as you may be tempted to use other types of solder, such as plumbers' solder which may have different proportions. The type of lead you need is frequently advertised in the motoring magazines or you could get it from specialist motor factors.
I recommend lead and lead kits from http://www.eastwoodco.com/
I have used plumber's solder and it seems to work all right, (although the melting point is different) but it is best if you stick to the correct lead.
Make sure you order plenty of lead because,
a) You will use more than you expect, even when you get it right, and
b) You will put most of it onto the garage floor as you start to learn the skill!
To be continued: Look for my next post on Tools requred for Lead working.
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