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How to replace your classic windscreen

How to replace your classic windscreen Classic and Performance Car

Ever had a chip or crack in a classic car windscreen? With rare exotics or low-volume classics, finding a replacement can sometimes be impossible. Here’s what you need to do

You’re driving your rare classic car without a care in the world. Suddenly you’re on a piece of recently resurfaced road, loose chippings are everywhere and one whacks your windscreen. If it’s laminated, it now has a big chip or, worse, a crack. If it’s toughened, it’s now an opaque mass of shattered fragments. What now?
Clearly you need a new windscreen, as also you might if your old one is simply scratched or has gone cloudy around the edges. How on earth will you get one for your 50-year-old car of which barely a handful now survive?
It’s not widely known that Pilkington, parent company of Triplex, among others, has with commendable foresight kept the wooden shaping jigs it has used since the 1950s when manufacturing glass for new cars. Today it has centralised them at its hub for classic glassware, the Pilkington factory at Queenborough, on the Isle of Sheppey, north Kent. The jigs held there are not just for British cars with Triplex glass but for many European and Japanese classics too. So if, for example, you have a Ferrari 275 GTB, a Citroën Ami 6, a Lancia Flavia Vignale convertible or even an Amphicar, you’re in luck.
Otherwise, your windscreen will have to be specially made. For this, Pilkington needs an old windscreen to measure, accurate drawings, or the car itself. 
Or, if you happen to have had your car 3D-scanned so that all of its curves are committed to computer, that will do nicely. With these measurements a new jig can be made, over which the temporarily heat-softened glass will later droop.
So, what is the process? First, two thin sheets of flat glass are cut to the required outline. Next they are heated to over 500°C and each is laid in turn over the jig. Once cooled, one of the now correctly curved sheets is placed over the other with a polyvinyl butyral (PVB) plastic layer, opaque at this stage, in between. The edges are sealed together and the assembly enters a pressurised autoclave oven, where it is cooked for 2.5 hours at 1455°C and 10bar of pressure.
After this, the PVB is both clear and bonded to the glass, and once the edges are smoothed the new windscreen is complete. Making a one-off windscreen (or rear window) is not a cheap process, but should anyone need another it will be much cheaper next time. Meanwhile, stay away from loose chippings.

Words: John Simister

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