Yellow algae has built up on the rubber window seals of my Seat Ateca. I suspect it's a reaction to pollen sap from a birch tree next to the drive where the car is parked. We have since had the tree felled, but how can I remove the algae?

- BH

Algae, moss or lichen growing on window seals is a common occurrence in Britain, where our damp climate and frequent rain means that window rubbers can stay moist for longer.

This moisture is a great breeding ground for moss or algae, allowing it to take root and grow, all the more likely when a car is parked in the shade and the sun can't dry the seals - for example, when it's parked beneath a tree for long periods.

This moss can be surprisingly tenacious and difficult to remove permanently. Even when it's dry, it doesn't simply die - it can stay dormant for long periods, waiting for more moisture to allow it to continue to grow.

It doesn't simply wipe off, either. You'll need a pretty heavy-duty cleaner and a good scrubbing brush to get rid of it.

This is where most people stop - and it's also where most people go wrong, because unless you kill the moss as well as cleaning it, it will grow back.

My suggestion is to first use a fungicidal cleaner to kill what's there. Use a toothbrush or a cotton bud and apply it carefully, to avoid the risk of damaging the paintwork.

A couple of days later, once the cleaner has taken effect, use a heavy-duty car cleaning fluid such as G101 to remove whatever is left behind, again using a toothbrush to enable you to apply it accurately.

Finally, spray the seals with a rubber conditioner, such as Autoglym's Vinyl & Rubber Care, to keep them flexible and prevent them drying out. This last step is optional, although I find it's easier to maintain your car's window and door seals than to have to replace them later if they perish.

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