John Simister
The home painter has it easier than ever, says John
Our John busts some myths about modern paints and their use.
Today’s car paints are amazing substances. I have polished the family Toyota, run by us since new in 2001, just twice in all those years and rainwater still settles as separate droplets on the shiny surface. I have yet to polish either my Saab 96 since its repaint in 2013 or my Stiletto repainted in 2015, and both still sparkle. And even the aerosol paint sprays we buy are better than they used to be, less likely to react or to sink into the edges of repairs involving body filler.
Not so very long ago, you could often tell a car that had been to a bodyshop because the repaired part would go dull, especially if it was red. Or the paint surface might be rough and orange-peely, as though the paint had dried too quickly or the spray pattern wasn’t atomised enough. Nowadays, though, every bodyshop seems to achieve a properly smooth, shiny surface and blow-ins are practically undetectable.
We have modern paint materials to thank for this, materials which are easier and more forgiving to use. In fact, these paints have been around since the late Seventies, but it was a while before the whole refinishing trade adopted them. Sometimes this was because customers insisted on the ‘original’ material, because it was the right thing to do. Except, mostly, it wasn’t.
Cellulose and two-pack myths
There is a notion among some lovers of old cars that classic cars were painted with cellulose products at the factory. They nearly always weren’t, at least since the early Fifties, unless they were Grp-bodied and/or built in very low volumes, in both cases precluding the use of high-temperature baking ovens. Cellulose was too finicky to use, needed too much post-application polishing, was dangerously inflammable, tended to dull quickly and, being brittle when fully hardened, was prone to chips. Petrol could attack it, too.
However, the paints that were used most often for post-war classics aren’t readily available either, because they have been superseded by better ones. Ah yes, you say, two-pack. That’s a generic term for a paint system in which a small amount of hardener is mixed, after which you had better spray pretty quickly. Another refinishing myth has grown up around two-pack, which is that it looks too thick and shiny as though the car has been dipped in molten plastic. Yes, it can look like that, but only if it’s applied too thickly by someone in a hurry. Applied properly, it looks factory-original. So, with what were our cars painted originally? Back in 1923, chemical company Du Pont invented nitrocellulose lacquer. Its quick-drying properties were perfect for the new age of mass production, but by the late Thirties there was a better product: alkyd-based enamels, whose finish could be made yet tougher by baking the bodies as the paint hardened. Then, in the Sixties and pioneered in the UK by Vauxhall, came thermoplastic acrylic lacquer. Here, the heat of the baking oven melted the just-applied paint, which underwent ‘thermal re-flow’ and then solidified with an ultra-glossy surface. So said the ads, anyway.
Other carmakers gradually adopted the new acrylics. Since then, tougher acrylic enamels (now often water-based) have replaced acrylic lacquers, and a clear coat is used over solid colours as well as metallics. No wonder the finishes last so well.
You can’t go cooking bodies in the aftermarket, though, so two-pack paints can be had, if nonmetallic, as ‘direct gloss’, requiring no lacquer and mimicking a period look. And if the rest of a car’s paint has dulled a bit, a matting agent can calm down the new paint’s gloss.
So, where does this leave the do-it-yourselfer? Today’s aerosol paints are usually acrylic enamels, their solvents less aggressive than those of the cellulose days. If you want to go the spray-gun route, though, and you lack your own tank-fed breathing apparatus and a spray booth with air extraction, cellulose can still be obtained. Just.
The last time I sprayed a whole car in cellulose was in 1995. Since then, I’ve left spray jobs to the professionals – and the result stays with you long after the financial pain has passed.