II VI say use acetone and cotton swab or cotton ball
For cleaning optics
Proper Cleaning Method
In any optics cleaning process, the goal is to remove contamination
from the optic’s surfaces without further contaminating or damaging
them. To this end, the user always should begin with the least risky
cleaning method and progress to more stringent methods only if
necessary. The steps outlined here are in the order in which they
should be taken by the optic user, beginning with the least risky
The first step in any optics cleaning process is to use an air bulb
to remove loose contamination from the surface. For optics with
minor particulate or lint on their surfaces, this step may be all
that is necessary. Shop air lines should not be used for this step,
because compressed air contains oil and water, which will further
contaminate the optic.
The next step in the process is a light cleaning with reagent-grade
(also known as spectroscopic or HPLC) acetone (see Figure 1).
These finer grades of acetone are nearly water-free, which minimizes
the possibility of streaking or contaminating the optic.
A cotton swab dampened with acetone should be used to clean the
optic surfaces in a light-pressure, circular motion. The swab should
be changed if it becomes contaminated. Cleaning is completed with
slow, straight strokes to prevent streaks from forming.
If the optic has two coated surfaces (such as a lens does), both sides
should be cleaned in this way. The first side needs to be placed on
a clean layer of lens tissue to protect it during this step.
If the acetone cleaning fails to remove all contamination, the next
step is to use acetic acid to clean the surface. Acetic acid cleans by
dissolving certain contaminants, but it will not harm the optic’s
substrate or coatings. This acetic acid can be laboratory-grade
(diluted to 50 percent strength) or even common household white
vinegar, which is 6 percent acetic acid.
The cleaning procedure is the same as outlined for acetone,
followed by a final acetone cleaning to remove the acid and dry
the surface. During the final acetone cleaning, the cotton swabs
should be changed frequently to allow the acid/water mixture to be
absorbed completely from the optic surface.