Plastic changed our lives. It certainly changed how we build our cars. If nothing else, polyester-based body fillers let amateurs plane their cars' bodies faster and straighter than even professionals could ever dream of with lead. It doesn't require a torch, arcane tools, or extensive training. Even when sanded it doesn't threaten to poison its users with heavy metals (sanding lead suspends particles, which inevitably enter the lungs or eyes). All hail pink lead, the fantastic plastic.
But as we found out, plastic fillers didn't do everything better than lead. Even when troweled across a panel it'll last forever but build up an edge with it and it will inevitably chip. Spread it across an area prone to movement or extreme vibration and it will crack. Oils that porous plastic fillers absorb if left bare will positively wreck paint finish from the bottom up. At least for those occasions we're forced to pick our poison: plastic that may fail in one of those applications or literally pick poison.
We have a third option now. In fact it's existed for decades—for health reasons the OEMs adopted lead-free solders in the late '70s and over the last generation they've all but replaced lead-based solders in our market. Rather than 70 percent lead and 30 percent tin these new-age solders contain mostly tin and lesser concentrations of copper and zinc.
This isn't one of those alternatives that sacrifices performance for safety. Johnson Manufacturing Company, the manufacturer that developed the lead-free solders for GM and Ford in the 1970s, makes the lead-free solder alloy for Eastwood. It does everything lead-tin solder does. It applies by the same process and uses the same tools as conventional lead-based solder. In application it actually works better. For starters Johnson brags that its lead-free alloy is half again stronger (9,000-psi tensile strength) than lead-based (6,000-psi) solders.
And as we discovered when Marshall Woolery at Thun Field Rod & Custom tried his hand at Eastwood's kit in the Oct. 2010 issue, lead-free solders actually make life easier. They work at higher temperature but they remain plastic (workable) over a broader temperature range. Lead remains plastic from 361 to 496 degrees F whereas the lead-free solder softens at 428 and remains plastic all the way to 932 degrees. (Note: a misinterpretation of the directions in the Oct. 2010 issue led us to incorrectly state that lead-free solder had a narrower range but we know this to not be the case.) That translates to nearly four times the temperature range of lead-based solder. And that's great news for anyone who's laboriously paddled the perfect lump of lead only to have it roll off the panel in a glittery mess. You almost have to work to remove this stuff. Almost.
Lead-free body solder has another distinct advantage: You can sand it. For that matter you could take a high-speed grinder to it and broadcast the dust across the shop. It's still prudent to wear a mask to prevent inhaling the dust (tin in high quantities isn't great for you) but it doesn't present the extreme toxicity that lead does.
As great as tin-zinc body solder is it still relies on the soldering process used to apply lead. It's not very difficult—millions of people have learned how to solder a panel, and not all of them are as smart as you and me (a lot were made dumb by lead poisoning due to sloppy handling). That part we couldn't do justice in the review of Eastwood's kit but we can here.
Application requires an absolutely clean surface, a tinning step, and only then can solder meet a panel. It also requires the same protective measures, particularly eye protection. And before you write to tell us, yes we're fully aware that Woolery didn't wear his goggles at all times. But that they're on his head should explain that it wasn't for pride or ignorance. It's a mistake anyone could make but it's not one worth repeating.
As noted in the Eastwood product review Woolery was more than just a little skeptical. But his opinion changed when he started working it into place. He picked up on the temperature difference immediately and though he hadn't slung lead recently he took right to the job.
So is lead-free body solder the ultimate filler? Of course it's not, but neither is the lead it replaces or the plastic that it outperforms. Each has distinct advantages and disadvantages. That said, as long as the lead-free alternative is available there are few legitimate reasons to ever use lead-based body solders again. It works easier, takes more abuse, and as the OEMs have proven over the past 30-plus years, stands the test of time. Finally, a safer alternative that works better than the material it replaces.