The original soft coatings were very soft indeed and could not be cleaned at all, but the term 'soft coating' is now used for 'old hard coatings that aren't as hard as modern hard coatings' -- which includes Leica's older coatings.
Cheers,
R.
To clarify, it seems simple now, but in the early 70s, Pentax discovered a way to bake their lenses that hardened lens coatings a
lot and fused the lens coatings to the glass. Pretty much everyone jumped on the band wagon and hard coating was born. Incidentally, the way it became fused to the glass is what made multicoating possible. before this, any attempt to coat an already coated lens simply removed the former coating. Any lenses made before this breakthrough are, in general usage, referred to as "soft coated" now. Technically, a real soft coating is one made before Leica developed their process of coating lenses. It is not a good idea to get ammonia near
any of these because the ammonia can, at very least, cause the coating to seperate from the glass. On the older lenses, that really were soft, the ammonia can literally eat the coatings away. On the
really soft coated lenses, anything beyond flushing with distilled water should be avoided like the plague.
There is yet another type of coating. There is a type of "tarnish" that sometimes develops on older lenses. It most often looks like a mottled irridescent oil slick. This is a type of natural coating called a "bloomed lens." In the old days, some people discovered that it increased the light gathering ability of a lens, decreased lens flare and improved contrast. They came to be in very high demand among astronomers and photographers and early lens coatings were an attempt to artificially recreate this "bloom." They still turn up every now and then and, once again, anything beyond a gentle rinse with distilled water should be avoided like the plague with these.
