Pour ceux que cela interresse mais desole c est en anglais si quelqu un se sent le courage de traduire.
Lens cleaning
By John B. Williams
It is important to know that if telescopic sight lens surfaces are not kept absolutely clean and free of mud, dust, water and oils the lens surfaces will degrade the image to the point to where one cannot use the scope effectively. Try to avoid cleaning as even the slightest abrasive scrubbing will ultimately scratch the surfaces to where the coatings are worn off or damaged. At this point the lens is left bare and actual glass degradation takes place.
So what methods and techniques can be employed by the shooter to lessen this situation?
Here are a few tips to prevent ruining your favorite scope.
1. Keep the lenses covered with dust proof and waterproof caps.
2. If possible have clear optical glass covers made and put screw-on or flip-up covers over them.
3. If you absolutely have to clean dust off the lens surfaces, use an artists camel hair, or similar, brush with the handle cut off. Make or buy a dust-proof container for the brush and try to keep it in the buttstock hole or handy to where you can use it promptly and effectively.
4. Do not put water on your scope lenses to “wash off” the lens surfaces. Water will attack the lens coatings and the lenses. Lenses are hygroscopic and amorphic in nature, meaning they are composed of a certain percentage of water and the molecular structure is always moving. If you look at glass windows in centuries old castle and buildings, you will notice the glass panes are sagging. Glass moves and therefore, gravity pulls the molecules of glass downward.
5. If you have to clean your lenses, use lint-free surgical Q-Tips or swabs and fresh filtered acetone. Pour a little acetone in a ceramic or clean metal cup (acetone will melt plastic). Dip the swab in the acetone and make a clean circular pass starting at the center of the lens. Throw the swab away (don’t dip back in the acetone because it will contaminate the acetone and the surface of the lens), and with another fresh swab, repeat the process until the lens is absolutely clean. Do not rub or scrub with a scrubbing motion, make a pass and with a clean acetone soaked swab, repeat the operation.
Don’t do’s:
a. Don’t wipe lenses off with dry clothes, lens pencils or coarse brushes.
b. Don’t put water on the lens.
c. Don’t leave lenses uncovered.
d. Don’t put your fingerprints on the lenses.
e. Don’t take a scope from a very warm interior of a building to the outside where it is cold. A shift of forty degrees in temperature variation will overcome the dissicant in the scope (if there is any), and fog the scope.