Hello,
Is the canada balsam used as "mounting medium for microscopy" the same or suitable for lens cementing?
I know there are UV optical adhesives but I like better the idea of using the original stuff in old lenses.
thanks for any input
Wagner Lungov
I think it will work for this. Having worked on recementing about 20 lenses by now I highly recommend you use something else, like Summers J-91, but if you want to try Balsam and report back on your experiences I would certainly be interested in how you make out. Good luck.
Canada balsam with it's refractive index nD 1.541 was mostly used by lensmakers. Other cements like Summers J-91 have a different refractive index, also the transmission of the cured cement is different, specially in the short wavelenght region. Depend on the glasses used, the character of the lens can be changed. But the most important advantage of canada balsam is it can easily removed when something goes wrong.
I don't consider heating a complex lens assembly to 325+ degrees F easy as a way of undoing mistakes. With the product I suggested you can soak the lens elements in MEK at room temperature and in about a week they fall apart with no risk of breakage. The product I suggested is Summers' first recommendation for recementing lenses originally glued with balsam, at least as of a year ago.
But, again, I'd love to hear how somebody makes out with Balsam, so go for it. I think of the risk of breakage from heating all those elements up, holding them in position and gluing them before they cool and I want somebody else to try this and let me know how it goes.
The refractive index for what I suggested is 1.55. If balsam is 1.541 is this really going to make any difference whatsoever?
The cement will be so thin that the difference between a RI of 1.55 vs 1.541 is negligible. The only possible difference will be in the strength of the reflection!
I think the microscopy mounting balsam should be the same as the optical stuff, although possibly a little less pure.
Canada balsam solved in xylene, benzene and other solvents will be used without any heat. And also removed by soaking in a solvent. Of course removing by heat is faster but with a higher risk. Natural canada balsam has a too low pH, so it must be neutralized with calcium carbonate. But in xylene solved neutral canada balsam is aviable at stores for microscopical work. In this stores also synthetic cements are aviable. It's only important to choose such a cement with a refractive index nearly the same as canada blasam.
I've recemented some lenses with such cements. The advantage is one needs no uv to cure.
Some dyes used in microscopical work are very sensitive, much more as the most optical glasses. So the balsam used there will not attac optical glass. E. g. natural canada balsam used by warming the lens will ruin most microscopical slides by the low pH.Originally Posted by Ole Tjugen
That's the problem Ole. The best cement has the same refractive index and the same Abbe's number as one of the glasses glued together, so the reflection is only made by one refractive index jump.
"Canada balsam solved in xylene, benzene and other solvents will be used without any heat. And also removed by soaking in a solvent. Of course removing by heat is faster but with a higher risk. Natural canada balsam has a too low pH, so it must be neutralized with calcium carbonate. But in xylene solved neutral canada balsam is aviable at stores for microscopical work. In this stores also synthetic cements are aviable. It's only important to choose such a cement with a refractive index nearly the same as canada blasam."
Depending on the diameter of the glass, out gassing and shrinkage could cause a problem, like cracking the glass.
Ultraviolet LED lamps are fairly cheap now, check with any automotive tool company. They are used to check for leaks in an air conditioning system. They will set-up UV cement, the sun will do the rest.
Just a thought.
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