What do you call the paste between some lens elements?

[slashmaster]

I was taking apart a broken hi-8 video camera one day and found paste between one of the lense elements and its doublet. Wondering how well it would work to put this paste between a lens and its doublet on something that didn't originally come like that? Anyone know what this paste is and where to get it?

[granfer]

Always used to be a compound known as "Canada Balsam", but I don't know if that's what is used these days.

[aj]

I was taking apart a broken hi-8 video camera one day and found paste between one of the lense elements and its doublet. Wondering how well it would work to put this paste between a lens and its doublet on something that didn't originally come like that? Anyone know what this paste is and where to get it?

It will wreck the lenses. Kitting lenses has been around for 100 years and the idea that you as an amateur can improve a professional lensdesign by adding a kit is ridiculous.

[BAC]

Is there any way to repair a lens that has separation which I assume is the failure of this material. The reason I ask is I have a few inexpensive lenses that have separation but they are not worth sending in for professional repair. I seem to remember reading something about repairing separation years ago.

[slashmaster]

Thanks Granfer, Thanks AJ. So AJ, do you mean the stuff will eat away lens coating?

[aj]

Canada Balsam from existing kitted together lenses can be dissolved by keeping the lenses immersed in a solvent. After that you could attempt to kit them together again. You would need skills and insight along with a cleanroom workbench.

The kitting has a purpose in having a glass surface with fraction but without air between the two surfaces. Putting two surfaces together with kit which have not been calculated for that will influence the optical behaviour, not for the good.

[cameratech]

Canada Balsam hasn't been used to bond lens elements for many decades. These days manufacturers generally use UV cured optical cement, but there are a number of different products available. See:
http://www.optical-cement.com/cements/p ... chor720308
A cheaper option is to just use a consumer-grade glass glue like UHU Glass.

You can have a go at re-cementing doublets that have separation yourself, but if the centring alignment of the 2 elements is off the optical quality will be significantly diminished. A bit of dust in the join is not ideal but is far less of a problem.

Separation doesn't look pretty but it actually doesn't affect the image much at all until the separation is severe.

[granfer]

Canada Balsam hasn't been used to bond lens elements for many decades.

There you go then........ doesn't that just show my age!!!!!!!

[BAC]

The lens I was thinking of repairing is over 70 years old so they probably did use Canada Balsam. It probably doesn't have a coating either. Canada Balsam is still readily available, they use it to preserve microscope slides but a bottle costs more than the camera I'd like to repair. Maybe I should just turn it into a pinhole camera, it's an old Voigtlander, not a cine camera.