Binoculars Prismatic No5 repair

[Peter Laidler]

Methylated spirit will break down SOME forms of Canada Balsam in my experience. But why it won't break down some others that are clearly Canada Balsam, heaven only knows. Best for taking it off is old carbon tetrachloride as taught to me in the 60's but, alas, now banned. Trichlorethylene is a good second best but MUST be wiped off with surgical/pure MS before assembly to clear any residue.

M.S. is just my abbreviation for Methylated spirit. Just to reiterate. I use industrial meths for general cleaning but before final assembly I clean all lenses, prism's etc etc with PURE/Surgical MS to be 1000% certain of cleanliness.

Occasionally you'll get a layer of balsam or other adhesive that you just can't get off a lens, generally around the edges! We used to use a piece of thin/.005" or so brass shim to gently scratch/scrape it away. The shim won't attack the glass.