What's the cause of oily sticky aperture blades?

My prized 50/1.4 AIS Nikkor suddenly has a fair bit of oil on its aperture blades. It was fine about six months ago.

So, obviously it'll have to be taken apart and cleaned up.

That lens was bought new in 1988 with a new F3/T. It's been used and taken care of.

I've checked older lenses and they're fine.

What causes this - warm temperatures?

Normally, I leave my lenses on camera bodies, so the blades are usually at full aperture. Would it be better to remove the lenses and have them closed down to minimum aperture?

Theo,


That's something I really wanted to know but never thought about asking...


Cheers,
Flavio

I've always thought it was caused by a breaking down of the lubricant in the focusing helicoil (or is it helicoid?), only because AFAIK, that's the only lubricant in a typical lens.

There is lube on the focusing threads/helicoil. Warm temps may cause the lube to migrate. It happened to me on my Nikkor 50f1.4 too and the sticky aperture blades damaged the aperture control arm of my F4 camera. $100 repair for the camera. It's about the same to clean the lens I think.

Aha - and the lower blades have the oil. Makes sense that oil from the helicoidals are moving down by gravity.

Maybe some warm temperatures this summer finally broke the lubricants down.

I have a bunch of lenses w/leaked oil, many brands, and I have central air, which I keep cold.

Lubricants are an extremely complex subject, with entire college courses addressing them.

The lubricant in the focusing helicoid is the only one in most lenses.
So that is undoubtedly the source of your problem.

Unfortunately, the only solution is to completely disassemble the lens, then put the blades and all related components in an ultrasonic cleaner to totally remove the lubricant. That's quite time-consuming ($).

- Leigh

I use 90% (or is it 92%) alcohol from Walgreens. Works a charm, and leaves no residue.

To really do it right, you would also need to completely disassemble the lens, remove all of the old lubricant, and reapply.

Theo Sulphate said:

My prized 50/1.4 AIS Nikkor suddenly has a fair bit of oil on its aperture blades. It was fine about six months ago.

So, obviously it'll have to be taken apart and cleaned up.

That lens was bought new in 1988 with a new F3/T. It's been used and taken care of.

I've checked older lenses and they're fine.

What causes this - warm temperatures?

Normally, I leave my lenses on camera bodies, so the blades are usually at full aperture. Would it be better to remove the lenses and have them closed down to minimum aperture?

Click to expand...

I suppose that in extremely hot conditions it's possible that some grease types may be encouraged to migrate from focus threads (Eg extended time in a hot car). I avoid this for obvious reasons so cannot offer any direct observations. But generally aperture blades become contaminated by lubricant residue. Greases are typically comprised of solid and liquid components. As they age eventually these components can separate, inducing either oils to flow onto interior lens surfaces such as the aperture blades, or evaporation to occur which results in a greasy or oily residue to form on the blades and usually interior lens surfaces as well for obvious reasons. As lubricant viscosity generally decreases with increasing temperature it should not be surprising that the process might be hastened by warmer temperatures.

You can speculate about the pros and cons of leaving a lens wide open or stopped down but it really is only that. Any benefit of one or the other position might well vary, depending on the lens, and bear in mind that, if it exists at all, it would be marginal, at best, because the blades remain inside the lens at all times, where portions of them will be exposed to the contamination, no matter what f stop they're stored at. Once put back into use, any contamination of almost any part of the blade surface is typically going to spread across the blades entirely, due the way they interact with each other as they're opened and closed. Hence, even if a benefit existed in the first place, (of which, I'm personally very doubtful), it would be forfeited as soon as the lens was subjected to enough usage to spread the contamination across the blades, unless they were first cleaned.

It is also worth noting that contamination can occur in lenses that do not feature a helical type focus arrangement. Eg Rollei twin lens reflexes, as found, often have sticky shutter and aperture blades, even though they use a strut type of focus system driven by eccentric cams (except for some of the earliest models). They can however be prone to contamination as a result of the oils and greases originally applied to the Compur shutters fitted to their taking lenses which, like helical greases, will eventually break down and evaporate some residue onto the shutter and aperture blades.
Cheers
Brett

Thanks everyone. I suppose that in 28 years of service (1988-today), it's not unreasonable that I'll have to get this lens cleaned up and re-lubricated.

For dissolving the grease acetone is s good solvent, stronger than alcohol, available at Homedepot.

tedr1 said:

For dissolving the grease acetone is s good solvent, stronger than alcohol, available at Homedepot.

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Nail polish remover is a solution of acetone in ethyl alcohol. It's sold in small quantities and may be a good alternative if you can't source pure acetone in your area. It will contain some water, though.

Another good degreaser is benzine (cyclohexane). It may be even harder to source than acetone, but is guaranteed to be free from water. It also dries *really* fast!


Cheers,
Flavio

This appears to be an issue with certain lenses more than others and it could be related to the lubricants used, the construction of the lens, or both. I have a 100mm Pen lens with sticky blades and various other Pen lenses with slow blades. I have heard from various sources that this is a known issue with Pen lenses.

thug gins said:

... related to the lubricants used....

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Like the lube used in old Agfa folders which turns into a green glue.

Leaving a lens in a car can cause the lubricants to migrate to the iris and the shutter.

I know of this problem from working on a lot of Carl Zeiss Jena and Meyer-Görlitz lenses. The problem there was simply the economic system not enabling the manufacturers to get better lubricants. They either get stiff and wax-like or they vanish and focusing gets jerky and irregular.
The wax grease is not so much a problem for the aperture as it apparently was only used in the silver Alu lenses and they have a preset aperture only. These also are the lenses with a lot of blades, 10, 12 and above, the wandering oil from the grease works as a glue and when 15 oily, greasy blades get moved by a ring but are almost fused together, they tend to get kinked and / or pop out of their rail or stop.
The grease from the black or MC lenses tends to vanish completely, the oily part of it ends on the aperture blades and sticks them together. Happens mostly to the 2,4 Flektogons and Pancolars.
I don't know about those older greases, but modern ones are often comprised of two main parts: a solid spongy material (e.g. a Lithium compound) and an oil. When the focusing ring is turned the pressure pushes the oil out of the grease, lubricates the helicoid and gets soaked up again when the pressure is taken off the ring. Over time, these greases separate and oil tends to creep everywhere, I also found oil under lens name rings.
There is also a word for this kind of oil in German: "Kriechöl", meaning "creeping oil". It gets everywhere.
Also, after reading repair manuals of the old Zeiss Jena lenses, I can tell you that they used I think it was Molybdenum oxide or something on the blades to make them glide better. This and the oil and it sticks like Sticky the stick insect.

I experimented on blade cleaning with Goof-Off (acetone and xylene), and it has worked very well. It evaporates quickly, can be put on a cotton swab or microfiber cloth to actually remove debris, and leaves no residue. I only use it on lenses that I'm not taking the blades out of, and only if they are just showing the beginnings of oil. I use the 91% alcohol in a dish when doing full blade removal.

Ok... I've checked my other Nikon lenses. Only this 50/1.4 AIS new-in-1988 lens has the problem. Newer lenses do not and even a dozen older pre-AI lenses from the mid-1960's do not.

So, I'm still surprised that this lens has the problem. I can attest that it's never seen temperatures over 85F or under 45F (even then not for long) and it's had a fairly pampered life.

Maybe Nikon changed lubricants during the period my lens was manufactured.

My 50f1.4 was babied too.

Reference post #7. Grease is oil in a soap base. The type of oil and base varies with application. As technology progresses so does the materials used in the base and the composition of the oil additives.
As the grease ages the oil separates from the base. Somewhere there is a Nikon service manual that covers that lens that will list the lubricants specification for that lens. It may explain why that one failed and lens manufactured before and after have not.

Theo Sulphate said:

Ok... I've checked my other Nikon lenses. Only this 50/1.4 AIS new-in-1988 lens has the problem. Newer lenses do not and even a dozen older pre-AI lenses from the mid-1960's do not.

So, I'm still surprised that this lens has the problem. I can attest that it's never seen temperatures over 85F or under 45F (even then not for long) and it's had a fairly pampered life.

Maybe Nikon changed lubricants during the period my lens was manufactured.

Click to expand...

This lens is known to have the lubricant migration problem (the AI version apparently does not).