No53 mk1 scope lens issue

[Merlin266]

Can anyone tell me if this issue I have with this lens is repairable, it appears to be separation I think within the glass. This is the inner of the two rear lenses of the scope

Information

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[henry r]

watch out there is a 109 on your 6!!!

i'll be watching this with interest as my no32 is the same.

[muffett.2008]

Sure can, soak in Acetone or Methylated spirits until the lens seperate, clean all old residue off with the same spirit.
Use Balsam glue to reglue lens, apply pressure to exclude air bubbles, clean up and reinstall.

That's the abreviated version, lots of fun but a great exercise. PL will probably add to this

[Peter Laidler]

Er........ sorry Muffer but sure can't in this case! That is an internal crack in the glass as detailed by the 'rainbow' caused by the .....Further physics needed to elaborate on why but this is part of a test called 'light transmission' that it'd fail. However, the RIGHT hand side is caused by the cement breaking down and can be cured. But the internal cracking has rendered the lens scrap. You might find that the bit(s) of lens fall out when you separate it. Sorry about that! You could try to hide it - and some experts do - but you can't defeat the laws of physics when it comes to rainbows and light refraction

[Merlin266]

I've noticed that when a slight bit of pressure is applied, all these scallope looking thingymejigs disappear. As its part of No53 scope that was only for spares, I thought I would pose the question. Right on the edge of the lens is a little ding, although there's no cracks in the glass, when I apply pressure here, the scollop disappears. Destined for the dusty bin, me thinks. I assume, balsam glue is like rockin horse s**t

[Peter Laidler]

Sounds like your lens CAN be separated and re-cemented. Of there's a small chip to the edges of the glass you can spot it in (and we often would) with matt black paint. Best to do it with the rearmost lens when you have a pair of lenses because the eye looks through the rear lens onto the front lens and........ blah blah blah....... Anyway any blemishes like a paint spot-in or a slight scratch are less obtrusive when at the rear. It's getting complicated now so........

[bigduke6]

I assume, balsam glue is like rockin horse s**t

No its still available, had mine for some time (from ebay) takes a long time to cure so patience is the key. see link below will give some idea of the process.

Binoculars Prismatic No5 repair

[muffett.2008]

Try your local Art Shop, Balsam Glue is sold as a Hobby glue(usually made in China) under various trade names, but still the same stuff and used for gluing nearly everything.......according to the labels.

Pete, I saw the scallops and the mark near the finger that looked like a chip, but I've been surprised before to find the lenses still intact........always live in hope.

[RobD]

Canada balsam used to be used very extensively (by the gallon) to secure coverslips to millions of microscopy slides in pathology labs all over the globe. Every lab. had bottles and bottles of the stuff. It was also used as a medium to bond glass elements together, as in old scopes.
However, though it is clear in a thin film, Canada balsam does yellow with age, and dries out leaving the lenses with crystalline debris between them: but it can be dissolved and solvents can be used to remove it - time and patience being essential if the solvent is to penetrate from the edges, between layers of glass.
In the last 20+ years, Canada balsam has been replaced in pathology labs by Acrytol and similar mounting media.

[Peter Laidler]

Careful application of heat was what I was always taught to break old Canad Balsam down. Right from microscope slides in school Chemistry lessons to yesterday.........