Originally posted by Not a Number
I've used soap and water. I use Ivory soap. Detergents like Dawn have all sorts of enzymes and stuff in them. You never know what those will do.
I've had to clean off kid's sticky candy, tree sap, smoke residue, sprays from angry/frightened insects, mucilage from sundew plants, nectar from flowers and pitcher plants, salt water spray, dog nose prints, etc.
And yes, I usually use a UV filter to keep these off my lenses.
As Robert Capa is quoted as saying: "If your pictures aren't good enough, you're not close enough".
We used Dawn for years on glasses because it is a surfactant, and helps defog the lenses or the inside of a diving mask. But so is soap. And soap is a sort of detergent (alkali salt of fatty acid, or so I'm told). Both some soaps and some other detergents have other stuff like whiteners and aromatics and so on. Ivory soap might have less of those; I dunno.
I have had a lot of the same things on my lenses and filters. Salt spray is another, beer, and of course fingerprints. I've been using Dawn on the filters with good results (clean, no residue). Note there are several varieties of Dawn; I don't think all contain the enzymes, which are used to break down organics like lasagna. I doubt they'd have any effect on your lenses. Dawn is rather famous for being the cleaner of choice for birds that swim in oil tanker spills and such. Note that to use it for its surfactant qualities you leave some ON the lens or filter on purpose.
Some say that alcohol in cleaners wrecks anti glare coating, and I've seen some opticians recommend against it. Yet it is commonly used in cleaning lenses with high zoot coatings. I still use it on them. But eyeglasses get cleaned far more often, hence maybe that explains the difference.
Since most of the cleaners aren't required to even list ingredients, or just list some, it's really hard to figure out what's going on. But I agree that if you start with something really simple and well used like Ivory and water, and if it works, why risk other stuff. After all the point is to just get the junk off and if just water does it (like with salt spray) then that should do.