If You're Going to Bodge, Bodge Properly

There’s a moment – somewhere between the second mug of coffee and the fourth questionable decision – when a man realises he may have taken a slightly eccentric route to success. Not wrong, per se – just unorthodox, marginally chaotic, and undeniably abrasive.

This time, the problem was the 500SL’s door glass. After years of grit working its way into the window seals, winding up and down had etched a lovely set of vertical striations and hazing – the sort of wear that tells you the car’s been used properly. Most would ignore it. I couldn't. The orthodox method is polishing with cerium oxide, and I started with this, but it didn't make a dent.

I had a theory and, like most of my theories, it was perfectly sound in principle: apply the same logic as one does to car paint correction. Sand out the scratches with progressively finer abrasives until clarity is restored. Only instead of wet and dry, I turned to diamond polishing pads – the very ones I’d previously used to revive my limestone bathroom floor.

A diamond polishing pad is essentially synthetic diamond grit embedded in a resin or metal binder, attached to a flexible backing for use with polishing machines. The quality and consistency of the diamond grit – along with the bonding material – determine how aggressive, durable, and suitable the pad is for a given surface.

The mistake? I reused the old 3000-grade pad without thinking. It was still harbouring stubborn limestone particles in the matrix – tiny, gritty saboteurs from its last job. So instead of gently buffing out the striations, I created a rather beautiful spiderweb of circular scratches. More halos than a Michelangelo on the Sistine Chapel. The glass went from “lightly aged” to “attacked by a very angry cat wearing diamond shoes”.

You may ask why I didn't stop when I saw the first halos; however, when you're using water for lubrication there's no way you can see them. On top of that, the grinding creates a slurry that it's not possible to see through.

Now, I could have handed it over to a professional. But polishing a single door window tends to fall somewhere between “eye-watering” and “laughable” on the quote scale. And besides – the glass on the SL is very tough. Tempered, armoured, probably forged by dwarves under Stuttgart. This wasn’t a fragile pane waiting to crack – it could handle a bit of unorthodox encouragement.

So I regrouped, binned the limestone-laced pad, and ordered a new, clean set. This time I started with 1500 grit – aggressive, yes, and it left the glass slightly opaque at first, but it brought the surface back to flat in under an hour. A touch brutal, perhaps, but effective. The damage – both original and self-inflicted – was largely gone. As with paint, the first flatting is always the longest process and requires the removal of the largest amount of substrate. Subsequent polishing is far quicker.

From there, I worked up through 3000 and 6000 grade, gradually coaxing clarity back. 

And then came the magic: cerium oxide. At 1.2 microns, it’s so fine it makes talcum powder look like gravel. If it were graded, it would be about 100,000 grade. NASA uses it to polish astronaut visors. I used it on a Mercedes side window with a felt pad and just enough caution not to repeat myself. Cerium oxide particles do not break down or change shape during use – they remain consistent throughout polishing. Instead of cutting, they work by a gentle chemical interaction with the glass surface, smoothing it at a microscopic level.

And it worked. The result: smooth, distortion-free glass that looked better than it had in years. The shortcut had, as usual, started in calamity – but ended in triumph. The key is knowing how to reverse your own cock-ups with just enough gear, just enough skill, and a firm belief that there's no mess you can't polish your way out of.

The key to using diamond polishing pads effectively, similar to paintwork, is to ensure every last scratch is removed at the 1500-grade stage. Don’t fall into the trap of thinking a faint mark will disappear with the next, finer pad – it won’t. The surface needs to be completely flat before you move on, as the higher grades don’t correct – they merely refine what's already there. Use plenty of water throughout: I dip the pad in a bowl and keep the glass misted with a spray bottle, though a running hose would be ideal. And crucially, change the water in your bowl when stepping up to the next grit – otherwise, you'll carry over abrasive particles from the coarser stage, which rather defeats the point.

The moral? Clean your pads – especially if they’ve had intimate contact with limestone. But more importantly, don’t be afraid to do it wrong, so long as you’re willing to fix it right. Bodging isn’t failure. It’s just unfolding success.

And if all else fails – the window was scratched already, wasn’t it?

I now have another problem - on Saturday the after-market Clifford immobiliser and alarm decided to arm itself without my intervention, and there's nothing I can do to disarm it. Even disconnecting the battery overnight didn't help. I'm going to have to get professional assistance to remove the damned thing.