objective delamination.

[apochronaut]

Do objectives delaminate only during use or will they do so sitting in s drawer? I can't think of having acquired a verifiable n.o.s. objective that was delaminated ; only used ones !

[MicroBob]

Hi Phil,
I would say it is a combination of handling, stresses and brittle glue layers that leads to delamination. So it should be possible to find delamination in unused objectives, but maybe in undetectable numbers.
Another way to look at the question may be this: It probably is reasonable to expect that instruments of the same class but from different brands will be treated largely similar. If we find more delaminations in objectives of a certain type from one brand than from the other then it won't be the handling but the objective itself. If we find overall more delaminated objectives from one brand than from the other it may be that the less affected brand has never made eqivalents to the objectives that are delaminated from the other brand. This can probably explain to a certain degree the apparently higher delamination rate with Zeiss West optics, their basic achromats and C-eyepieces don't delaminate too.

Bob

[Hobbyst46]

FWIW:
My stock of delaminated Zeiss West optics:

A pair of 10x WF eyepieces
A 12.5x WF eyepiece
A 16x0.40 Neofluar Ph2
A 40x0.75 Ph2 Neofluar
A 100X1.25
A 63x1.4 Planapo Ph2 oil
All were received either by purchase or as gifts. All, except two, were already delaminated, but I noticed it too late.
The 40x0.75 became delaminated upon use, but it was never exposed to any stress (apart from ambient temperature and humidity fluctuations), so
it is the same as a "in-drawer delamination" case.
The 63x1.4 suffered short term water and glycerine immersions, afterwards slight delamination was noticed (not yet proved !) so a questionable case.

[Wes]

C-eyepieces don't delaminate

Thats probably because there is nothing to delaminate there, no cemented doublets and such. Maybe Zeiss knew the cement they chose would lead to delamination eventually so they could sell new optics in the future, kind of like planned obsolescence.

[apochronaut]

I wonder if light plays a major role? Do Zeiss West delamination frequencies reduce dramatically after a certain point in time? After perhaps they switched to synthetic cement(s). In the case of Bausch & Lomb, two notorious criminals from the Delami nation, the incidence of fouled doublets and triplets spiked dramatically after they switched to synthetic cement but I have not found an unused B & L objective that was delaminated.
One notable point too is that there seems to be a common factor affecting similar objectives . In disassembling multiple examples of identical objectives in order to attempt to rebuild one good one out of 2 or 3 duds, the offending cement joint is usually the same one in each objective. Bausch & Lomb 20X .50 flat field, Spencer 60X .85 dry and Zeiss 60X 1.0 oil with iris. Always the same elements. Doublets and triplets would be cemented in batches, likely by a single or small group of workers. Light concentration? Incompetent employee? Bad batch? Poor industrial design complicating assembly?

[Wes]

Some have suggested low temperature to promote delamination.

[PeteM]

In support of a sunlight-promotes-delamination theory - I once acquired an old OPMI Zeiss stereo scope with the worst delaminated eyepieces I'd ever seen. They looked like cataracts totally obscuring the view. The scope had apparently been stored near a window in an unheated space (but a temperate climate) - where sunlight could reach (and also periodically heat up) the eyepieces. I'd think that rapid thermal changes would be one culprit. Perhaps UV acting on the cement another.

The optics within were just fine.

[MicroBob]

In disassembling multiple examples of identical objectives in order to attempt to rebuild one good one out of 2 or 3 duds, the offending cement joint is usually the same one in each objective. Bausch & Lomb 20X .50 flat field, Spencer 60X .85 dry and Zeiss 60X 1.0 oil with iris. Always the same elements. Doublets and triplets would be cemented in batches, likely by a single or small group of workers. Light concentration? Incompetent employee? Bad batch? Poor industrial design complicating assembly?

There are also Zeiss and Leitz objectives that are much more often affected than others. E.g. the first Leitz Pl 100 1,32, effectively a Planapo. What may be the reason? Glass types with different expansion coefficients, curvature, layer thickness and evenness, UV hardening process?

[tlansing]

There is an interesting discussion on Zeiss lens delamination on Spike Walker's Ultraphot Shop site. Just scroll down the FAQ page to read his comments: http://www.the-ultraphot-shop.org.uk/faq.htm

[patta]

I have one objective (Wild Fluotar 50x) that delaminated in the center; but then some days it glues back; the day after, delaminated again. I've observed it for a while, and it seems in sync with the phases of the Moon.

Edit- some more guesses:

Against the theory that light exposure causes delamination:
The windshields of cars are made of two glass panels cemented together; they take quite a lot of sunlight; I've (almost) never seen a car windshield delaminated.
So it is possible in principle to make a cement that withstand heavy UV exposure.
The first synthetic cements, yes, likely were not properly tested, either against time or against UV.

The other theory, main culprit for delamination are the lenses made of different glasses, that when temperature changes they warp differently and detach. I remember reading a technical recommendation (Gross?), to make the cement layer thick enough so it allows a bit of movement between the lenses.
The worst warping difference happens to fluorite and fluor glass, and depends on the doublet geometry.
Large telescope objective doublets are usually not cemented, or "cemented" with liquid oil, to let the lenses deform freely; otherwise they'll warp, delaminate and crack in one day.
If the cement is stiff, it will break; Canada balsam remains always a bit soft instead, so the thick doublets where cementing with balsam was reliable, maybe wouldn't work with the new, hard UV curing resin. Also most resins, like plastics, contains "plasticizers" to keep them soft, but those evaporate with time, the resin becomes brittle and cracks (plus UV exposure degradation)