Black noses

[Tommyinyork]

Does anyone know why some aircraft have or did have black noses. Many aircraft have had black noses particularly in the 1970s and 1980s and many of these aircraft were MD80s, 737s, 747s, DC10s and Tristars, however an aircraft today with a black nose is hard to find, apart from the BA 757s which have a black ring around their nose cone.
What do or what did black nose cones mean, what were they for.

[Re-Heat]

BA 757s only have the black rings as they were trialling Microwave Landing Systems at Heathrow in the recent past.

[dada]

in th'olden days paint had lead in it. it now longer has and therefore radaome can be painted over.

[square leg]

Possibly the black noses, just below the windshields, were painted in such a manner to prevent glare from the sun.

[SeldomFixit]

Tommy - the black cone you are referring to is/was a rubberised coating to prevent/minimise erosion to the radome. Newer compounds are no longer as susceptible and as such, don't require such a coating.

[FJJP]

dada is correct. Radomes are made of a substance called 'neoprene', which was invisible to radar. It was usually manufactured in the colour black. It was found that the old paints interfered with the radar to such an extent that its performance was seriously degraded. Therefore, the neoprene cover was left unpainted.

Modern paints do not have that effect, therefore the radome can be painted in company colours.