How can balsam separation between glued elements be fixed?

I'm planning to try to fix a couple lenses because what else am I going to do with them?

It's about looking nice, optimizing image quality, and completeness. One of the lenses (Tamron SP 28-135/4-4.5) had a stuck zoom (with four moving groups), oily elements, and sticky residue, as well as the usual grit and grime that lenses collect after washing ashore on the beach. (Why do so many lenses have sand in them?) All that's left to finish is to fix the balsam separation and calibrate focus.

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    I think the received wisdom is 'you can't', at least not economically. – user82065 Apr 12 '19 at 14:32
  • Just use them: I've used lenses with element separation for years with no ill effect at all. If you want the lens to look pretty (for some value of pretty) then you can try to fix it, if you want a lens to take pictures with, don't bother. – user82065 Apr 12 '19 at 18:03

You disassemble the included elements, remove all of the balsom from both surfaces, and then glue them back together. To guarantee proper alignment when re-gluing them, you probably need some fairly advanced optical lab equipment or (for lower cost lenses) an original jig that the manufacturer may have used when the lens was made.

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