In the 60's Kodak developed what we now call "majic glue", Hot Stuff, crazy glue, etc. (the original formula was called Eastman 910) and it was developed specifically for gluing lens elements together because of some of the undesireable properties of balsam.

It is optically clear, VERY thin, self-wicking, does not grow fungus, cheap, stores in the frig, easy to work with after some practise.

It does not activate until it comes into contact with moisture, so keeping two lens elements absolutely dry will give time for repositioning as needed. An spray 'activator' can be used to kick it over when desired.

I have not used it to glue lens elements but have used a lot for other purposes: machine shop, inventions, etc. It can be the right stuff for the right reasons.

Perry