This LRO reader emailed LRO.firstname.lastname@example.org to ask Peter Galilee about cleaning the door-top window plastic sliders on his 1956 Land Rover Series I.
How can I clean the plastic sliders on my 1956 Series I’s door-top windows? I’ve tried to clean them with white spirit, but that didn’t help.
S Walton, Sunbury-on-Thames, Surrey
The problems are: horizontal scratches (from sliding); surface abrasion (from air-blown grit); oxidation (which causes most of the dull white look); stuck-on particles from atmospheric pollution (especially in industrial areas); small cracks that don’t necessarily penetrate all through the plastic; and star-crazing – tiny internal fracturing that shows when bright light is at an acute angle to the plastic. Nothing can be done about cracks and star-crazing, but unless they’re really serious they’re not the worst of your vision problems. The rest – basically, what’s on the surface of the plastic – can be dealt with.
To check the improvement that can be expected, add washing up liquid to water and wipe on both sides of the plastic. If the plastic is now clearer, it’s salvageable. You’ll need to wash the plastic anyway, getting right into corners to remove grit. If you don’t, it’ll pick up on your cloth during the next step – you’ll be wiping grit over the plastic and scratching it. Don’t use solvents; some may be too harsh.
Basically, you’re going to use an abrasive to get the rubbish off the plastic’s surface – but only avery fine, gentle abrasive, in the same way that T-Cut removes the dullness from car paint. T-Cut is too rough for this job, though, and contains ammonia.
Renovo Plastic Window Polish (for plastic rear windows on sports-car soft tops) is available but the tiny bottle is only just enough for a Series I’s sliders. So I also decided to try out Autoglym Super Resin Polish (£15 a litre at Halfords), which has a small amount of very fine abrasive in it. And, obviously, it’s useful for polishing cars afterwards.
I tested each on a scrap piece of Series I side-screen plastic and divided it up into three sections for tests, with each section having an untreated ‘control’ section, so I could judge the improvement, if any.
And the result…
Household glass cleaner gave a temporary improvement, but was back to dull in a few minutes. Renovo made a big improvement and the Super Resin Polish gave results more or less identical to Renovo. These last two produced a faint grey-brown residue – dirt removed from the plastic.
Following the test I taped over the rear half of the plastic slider on my Series I, and cleaned the front part with Super Resin Polish. Apply small amounts regularly to the cloth; work in a circular motion. Get to the hard-to-reach strip where the front glass overlaps the plastic slider by wrapping the rag around the end of a ruler.
Wipe to remove all residue, and polish. Next, apply small amounts of car-bodywork wax – I used Autoglym High Definition Wax. Rub it in thoroughly – the wax fills microscopic scratches. Then polish carefully.
This workshop advice appeared in the February 2016 issue of LRO. Back issues are available to download on digital devices here.