Advice Needed on Cleaning Filthy Lenses...

In my search for very fast but cheap lenses I have come across and

purchased some real dogs, many of which have really nasty stuff gooped on

the glass. I have a $5 Aero-Ektar which has what smells like pine sap on one

inside (!) element, as well as your 'standard' infirmary of f/3.5 Tessars with

measles, f/2.9 Pentacs with cataracts, and f/4.5 Xenars with fungus...

 

So, how does one clean them? I was advised that MEK (Methyl Ethyl

Ketone?) would clean them quite nicely (as well as cause early senility),

another person advised chemical-grade acetone, while another suggested

Methanol.

 

Great advice, I think, however, I can't find any of them here in New York City.

Does anyone have any suggestions for where one might find these, or other

chemicals which might do the trick? Any and all help is appreciated...

That pine sap is probably canada balsam, which is ..... pine sap. balsam was commonly used to mount lenses before modern adhesives were invented.

Methanol will work, but acetone works better. MEK should also work. Just make sure whatever you use is high purity (ideally spectroscopic grade or something called HPLC grade -- do a search for Aldrich or Sigma chemicals or Fisher Scientific). I had an old uncoated Angulon which gave dreadfully flat pictures. Took it apart, cleaned all the surfaces with HPLC acetone, and it completely revitalized the lens: the images are now sharp and contrasty. Still has some flare issues with direct light sources, but not too bad.

 

 

Canadian balsam was used for its refractive properties (I think) and index matching -- kept reflective losses down before the age of the quarter wave stack (coatings). And IIRC fungus etches glass, so those may be goners.

You should be able to find Acetone at any good paint store, possibly at a large art supply store.

Jason,

 

You might try IsoPropyl Alcohol as it removes all sorts of gunge and leaves no residue when it evaporates. It will dissolve real Canada Balsam given enough time but not the modern adhesives so try to keep it away from the edges of lens elements.

 

You can get it mixed with a little penetratibg oil but this leaves oily marks. So look for the pure stuff often found in radio Shack type places as electrical contact cleaner

Ether works very well, just be careful breathing it. Dip a q-tip in it and clean the glass in circles from the center to the edges. Either won't leave any traces.

Acetone and/or Methyl Ethyl Ketone (MEK) are ordinary and available on the shelf Hardware store items, usually around $10.00 per gallon. A slightly different version is called "lacquer thinner" which has various additives making it more suitable as a thinner but its still OK to use as a cleaner. Pure Ethanol is not readily available (190 Proof Russian Vodka is close enough for all practical purposes) but an intentionally corrupted version known as "denatured alcohol" also known as "shellac thinner" is a hardware store item. Same properties as ethanol except you can't drink it. These all evaporate cleanly and quickly which is what makes them suitable as cleaners. There is risk of damaging painted surfaces and plastic. (If, for example the edge of a lens is painted with black lacquer, it stands to reason that a product intended as lacquer thinner would damage it)

 

If you can remove the glass from the metal parts of the lens the very best thing to use is ordinary diswasher detergent, such as "Dawn" in lukewarm water and handle the lens like a champagne glass. (Champagne glasses are more easily damaged than the average lens element) If it were packaged as "Aqueous optical surfactant" people would be lining up to use it. Rinse with plain water after use and then apply clean compressed air to remove the remaining water. Don't allow droplets of water to stand on the surface of the glass. If left to stand on the glass and evaporate there is risk of damage to the glass around the edge of the water bead.