Hello,

Could someone help us out please? Everybody here talks about 'coating pits' as though they are fully familiar with what they are, but when interrogated, I don't think anyone is really sure at all. Googling the topic is not helpful.
The objects which we refer to as 'pits' has, typically, a small, dark, round centre, and is surrounded by a more diffuse area. The view through a microscope looks like the view of a lunar volcano seen from a great height.

An old document on coating blemishes, from Colts, states that a pit is caused by a coating build up over and around a small particle.

However, other sources explain 'pits' as coating overflows around cavities in the lens surfaces. The cavities are, presumably, due to lens surfacing operations. In this case, the term 'pit' would be an accurate description.

There is a third, less helpful definition, where any hardcoat speck whatsoever, is categorised as a 'pit'.

Any explanations, or opinions, which would help us,would be gladly received.

Best Regards,

Falstaff.