Cleaning OptoSigma/Thorlabs 1500 type GG?
 

I've searched through threads but found many differing opinions on cleaning ground glass but can't seem to find anything conclusive on cleaning these types of gg.. anybody have any tips?

I've tried compressed air but there still seems to be some dust on the gg (I've cleaned the rest of the lenses thoroughly so this is the last spot left). Ive heard some say to use soap and water, others pure alcohol or a cotton t shirt, and still others that say it's impossible to clean the gg without ruining it?

Would it be safe to take a regular lens brush to?

I tried with lens cleaning solution, but still the whatever-it-was remained. I then resorted to a lens cloth and ruined the GG.
$150 later and the Letus extreme is looking good again.

Cleaning Optics
 

Cleaning optics (glass) comes in several categories of "how clean". For typical optical applications (using lasers) I recommend to drag wipe optics. Never use acetone, tap water, Windex or anything as the final cleaning solution. Typically there is too much water/contaminants and you will leave that behind on the optics. I prefer to use a lab grade methanol (99.9 or 99.99 percent pure). Use a dedicated bottle and eye dropper for the solution. Begin the drag wiping process. If you see a resistant smudge or stain fold a lens paper and hold it in forceps and saturate the paper then clean the area. You may try this also in an-ultra sonic cleaner. If the stain persists it may be time for new optics. If the optics is coated (AR) only use the drag wipe process (carefully). There is another cleaning solution called Transene, typically found in FAB facility to clean contaminants off silicon. I have found this also to be a great cleaner for ultra clean surfaces. The final stage of clean optics would be to place the optics in a UV oven to remove even molecular condiments. - It all depends "how clean"...

I finally gave it a go and it looks like the worst spots may actually be imperfections on the ground glass, where a couple of tiny dots look like they've chipped away or are simply not present on the grainy side.. i actually touched the shiny side of the gg with my finger to rotate the gg in its holder until the spots were rotated out of viewable range (while monitoring on a 52" lcd) and the worst spots are out of frame now (i then wiped down the shiny side with a lens cloth)

Looks ok now, much better than before at least

When I had my optosigma glass I would wash my hands thoroughly, then rub the glass under warm tap water with dishwashing soap on my fingers. Then I would rinse thoroughly with distilled water.