'Grease' on lens elements

[GPS]

Actually I would like to know. Apart from obvious risks like damaging lens surfaces and coatings, and careless use of solvents, the only danger I can imagine is mis-alignment of cells on reassembly.

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Thanks to all for your interesting and helpful comments.

Baz.

Not only the alignment or the correct spacing but also the damage to stubborn spacing rings and threads, the quality of the air (dust) in your room (something you're concerned about a lot...), its humidity etc. It's not for no reason that assembling lenses is done in a strictly controlled environment and with a plenty of special equipment at hand. Unless you have all that and the know how then to disassemble a modern lens means to lower its value and performance.
Once I gave a lens for cleaning of some internal dust to a firm that was doing that. When I got it cleaned and commented on the presence of some residual dust in it the technician told me - that I cannot do as we don't have the sterile rooms they use for assembling of these lenses... In hearing that I appreciated his honesty....

[vpwphoto]

I just disassembled the cels of my old scrungy Wooley 7 1/4 Velosostigmat. IV.
Got the front ring off with the careful coaxing of a safety pin applying force in the "period" engraved in the ring. The rear cell came apart with the help of a rubber eraser pushed onto the ring and kept judiciously away from the element. The elements popped out of the brass with a little tapping of the ring on a countertop. Cleaned the inner haze and crud... almost as good as new. Hats off to the Woolensack folks for the wonderful machining. Neat to see pencil marks on the side of the elements form the 1930's.