Insect residue

In detail

Insect remains on a vehicle front, a window or a garden light are principally protein and lipid, which places them in the same treatment family as blood, milk and egg rather than with road grime. Two consequences follow directly from that classification. Heat sets them: a bonnet or a radiator grille is warm from the engine and hot in sun, so the protein denatures and bonds to the finish within hours in a way it would not on a cool surface. And hot water makes it worse rather than better, which is the opposite of the instinct — a protein deposit is softened by cool or lukewarm water and set by hot. The right approach is the standard protein one: soften with a cool, wet cloth left in place long enough for the deposit to rehydrate, then flood it away rather than rubbing, because the remains contain hard fragments that scratch. Acidic bodily fluids in some species add a chemical component that etches clear coat in the same way bird droppings do, so speed matters. Dedicated bug removers are usually mildly alkaline with a surfactant, which suits a protein deposit — though the caution about alkalis on aluminium trim stands.

Why

• Insect residue is explained by Heat-set stains