Archived posting to the Leica Users Group, 2011/04/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]This is going to be a long story, so those not interested or likely to be amused, stop reading here. During WWII, between undergraduate and graduate work, I was on the Manhattan Project in Chicago--yes, I'm THAT old. At one point, I was working with (for) a guy who was designing a lab instrument to be used where there was much radiation, i.e. had to be controlled remotely. He wanted mica absorbers of various thicknesses to be lowered on demand in the path of a particle beam. I became one of the world's best mica splitters! But we wanted thicker mica to carry these fragile foils. The problem was: how do you cement together a mica sandwich? Having been an amateur photographer, Kodak dry mounting tissue and a dry mounting press occurred to me as a possibility. It worked fine. But the day arrived when we had to disassemble one of those sandwiches. Knowing that dry mounting tissue is largely shellac, I decided to immerse them in alcohol. It did work, which is why I thought of that as a way of uncementing lenses. But here is the fun part of the story. As I was carrying down the hall a half gallon size beaker filled with 100% government-issue tax-free alcohol, the lab director asked he what the hell that was for. When I told him, he ordered me to color it with red ink to keep the janitorial staff from drinking it. Well, I got it nice and pink, but as I walked with it down the hall, a beam of sunlight hit it and it glowed the most brilliant, sickly, green. I guess the dye in that ink was fluorescein. Herb > > One thing is clear. The correspondent who said that Leica Wetzlar fixed > his > > yellow lens for free must have had this phenomenon. If bad balsam were > the > > problem, it seems to me that the lens would have had to be completely > > disassembled and the cemented element pair immersed in a solvent until > the > > balsam softened to where the elements could be safely separated and > > recemented. > >Herb, > >To separate cemented doublets or triplets you primarily use heat, not >a solvent. It would take years, maybe decades, for a solvent to get >into the cement enough to release the elements. > >Focal Point Lens can separate and recement with modern, stable cement, >lenses for you, for a remarkably good price. > >What exactly is going on with your lens I have no idea, but if you can >fix it with light, great. > >Marty > >_______________________________________________ >Leica Users Group. >See http://leica-users.org/mailman/listinfo/lug for more information -- Herbert Kanner kanner at acm.org 650-326-8204 Do not meddle in the affairs of cats, for they are subtle and will pee on your computer!