Too late to do anything now.
For years motorists have been advised that acid in bird lime was to blame for unsightly blemishes and patches on their cars' paintwork.
According to car care product specialists Autoglym, however, damage actually results from cooling paint lacquer which contracts and hardens around the deposits. The good news is that damage can usually be avoided – but only if owners act fast.
The firm's researchers say that when paint lacquer warms – in sunlight, for instance – it softens and expands. At the same time, the heat dries and hardens any bird droppings on the surface. But as the paint lacquer cools again, such as overnight, it contracts, hardens and moulds itself around the texture of the bird dropping.
Afterwards, the "moulding" appears as dulled or etched paintwork. The light's reflection is interrupted by the imperfect surface, unlike the undamaged surrounding paint which gives off a clearer reflection.
To test its theory, Autoglym attacked paintwork with strongly acidic, neutral and strongly alkali bird dropping substitutes, with negligible differences in the damage caused. However, differences in paint damage were noted when the substitute bird deposits had varying degrees of grain-to-liquid content. A grainier texture caused greater light distortion (dullness) when the paint moulded around it.
