As always, Barney, you're a fount of knowledge! I have copied your notes to
a file and will doubtless refer to them when I get to the bodywork stage
with my MG PA restoration.
Thanks for taking the time!
Lawrie
----------
> From: Barney Gaylord <barneymg@juno.com>
> To: Lawrie@britcars.com
> Cc: charlie@mars.ark.com; mgs@autox.team.net
> Subject: Re: patching rust holes? -- Body leading
> Date: Wednesday, January 14, 1998 10:47 AM
>
>
> On Wed, 14 Jan 1998 07:42:55 -0800 "Lawrie Alexander"
> <Lawrie@britcars.com> writes:
> >For us modernists convinced of the efficacy of Bondo, please explain (a)
> the benefits of lead, (b) where one obtains lead of the proper
> consistency for this job, (c) what method of heating you use and at what
> temperatures, and (d) how one prevents gravity from letting molten lead
> flow straight out of a repair area, for example on the underside of a
> rocker panel. Inquiring minds want to know....
>
> Wow! I nearly skipped this one until I noticed the word "lead". Since I
> have done this once in my entire life, I'll take a crack at it.
>
> Lead makes a (very) permanent repair if done right. It's strong, doesn't
> rust or corrode, doesn't deteriorate or crack from ultraviolet light or
> from flexing, and it takes paint well. It is especially good on a body
> panel that is subject to stresses and flexing. The thicker it is
> applied, the stronger the panel gets. This is an old technology that is
> still being used every day. Many new cars have a leaded joint where the
> roof (hard top) is attached to the body posts. It's a vanishing skill,
> but not a lost art.
>
> I understand the concern of some environmentalists and some health nuts,
> but the word is, just don't consume the stuff. If you melt it, drill it,
> file it, or hand sand it, it falls on the floor and you can sweep it up.
> However, if you have in mind to power sand it, you had best have a very
> good filter respirator mask.
>
> That said, it was not nearly as difficult to do as I had anticipated,
> took just a few minutes to get the hang of it, then came pretty easy.
> The first order of business is to get the steel surface clean and tinned
> so the lead will stick. Soldering on aluminum is a lost cause, because
> as soon as you apply heat it forms an oxide coating that prevents
> adhesion of the lead. Once the steel surface is tinned, the rest is a
> piece of cake.
>
> When lead melts it has a gradual transition from solid to liquid. It
> doesn't suddenly flow like melting ice into water. It behaves more like
> butter being warmed up until it is soft, the warmer it gets, the softer
> it gets. Too cold and you can't work it, too hot and it runs off. You
> play the flame of a torch around on the surface to apply heat evenly over
> a sizable area. When you get the surface temperature right you can push
> the lead around with a hardwood spatula like frosting a cake. You can
> even apply body lead to vertical surfaces. An inverted surface would
> probably be more of a challenge, but not impossible. Like bondo, you
> want to build it up slightly above the surface. Once it cools you just
> file it to the finished shape, and it's very easy to file. I understand
> that the current day skilled technicians on the production line can
> usually get it smooth enough on initial application without sanding or
> filing.
>
> The "lead" is actually a tin-lead alloy like solder. You need the right
> alloy, either 50-50 or 60-40, I don't recall at the moment, but if you
> buy it at the body materials supply place you get the right stuff. It
> typically comes in half pound bars, long and skinny. Last time I bought
> a bunch and only used a little, so I probably have a life time supply
> left over. If you're careful, most of it should end up on the car body
> and very little on the floor, so there should not be much waste. Don't
> try using the lead from an old battery or wheel weights, those would be
> nearly pure lead with no tin. You would also need a hardwood spatula, a
> bottle of soldering acid, and some of those little pencil brushes to
> spread the acid on the hot surface.
>
> My car now has another 10 years and 125,000 more miles on it. It's ready
> for a little more body work and a repaint, but that spot with the lead on
> it still looks like new.
>
> Barney Gaylord
> 1958 MGA with an attitude
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