The condition of a lens for reviews and tests can be any, until it doesn’t affect image quality and testing process. ‘Oiled aperture’ is in the list of such typical issues, but visible oil or stacked blades can significantly affect the price, so, it helps to save money of tester. And that’s would be great, if defect can be repaired without big efforts.
Note: demonstrated method isn’t a silver bullet – owner still needs a number of tools, skills and time.
Common recommendations about cleaning ‘oil on blades’ contain the idea of fully disassembling of the aperture mechanics, but in some cases there is no need to go so deep. Yes, taking apart of blades doesn’t require a rocket science or special skills, but there are a few disadvantages:
- It requires a time depends of design and personal skills, 30 mins minimum for simple case and up for a few hours
- Blades are thin, and risk of damage is possible
- Old mechanics elements fit together for a long time and can change behavior after reassembling
- There is a risk that old parts will be difficult to take apart. I had a case where one of the three screws fixing ‘mug’ with blades in the hull – simply could not be unscrewed (was drilled with followed threading another diameter – it’s not good at all)
The method of solvent liquids bath can help to save time and reduce risks, but need to remember, that it is available only for mechanisms designed without materials, which can be damaged by solvent. So, here is the disclaimer: think before doing.
UPD #1: In the video I used mix of 15% Ethanol, 10% Butanol, 50% Toluene, 7% Acetone, 10% Butyl acetate, 8% 2-Ethoxyethanol – it’s pre-prepared liquid for removing paints and greases, works great, but I believe that simple acetone is enough for common lens greases. Of course you can experiment with other solvent liquids depends of your fantasy.
UPD #2: If you prefer to avoid acetone, than can use ‘Naphtha’ based liquids (based on comments by Maury Jacks, collectors community) or lighter gasoline based liquids.
UPD #3: Actually, humans invented a lot of different solvents. Just use one what is available in your country and can’t damages aperture or you – a liquid which will remove oil and nothing more.
Minolta MC Rokkor-PF f=55mm 1:1.7 was taken for demonstration, but method works with a big number of short and long lenses up to MD-III era at least, also as a lot of Nikon, Canon, Pentax, Carl Zeiss etc.
And again: it need to follow all safety rules if working with solvents, and be careful to not to damage a lens – some liquids are very aggressive.
By the way – it is always better to clean not only blades but everything inside and change the grease of helicoid.
Have a nice day!