Cleaning solution seems to have left some sort of antifog

[ImmortalBee]

Hi there,

I took a pair of binoculars on holiday but unfortunately had an accident which left them with what I thought was a scratch on one of the objective lenses. I was very keen to use the binoculars (I had replaced a broken pair of 10x50s especially for this rare opportunity of dark skies), so I went to a local camera shop and bought a lens cleaning kit and cleaned them. Thankfully after cleaning them I was able to confirm they were not scratched and it was just some residue of some sort. However since returning home I have noticed that the objectives no longer fog up when I breathe on them so I think the cleaning solution has left some sort of antifog substance on the lenses. Is this likely to damage the coatings on the lenses? The ingredients of the solution are listed as "Distilled water with surfactant, glass cleaning detergent, Alcohol/Ammonia free" if this is any help.

 

Thanks,

ImmortalBee

[Ruud]

The fogging is probably is probably prevented by some sort of greasy or soapy residu, left after the water evaporated.

Your lenses aren't plastic. They're glass and the coatings are mineral. Alcohol should be no problem. Isopropyl alcohol without additives is a good cleaning solution. Apply it on some cotton and clean the lens. Just moisten the cotton, don't soak it. Remove any remaining liquid from the lens with a tissue (the regular type: no added lotion or anything like it). You may see rainbow streaks, which are easily removed by breathing on the lens and gently wiping it with a tissue. 

Ordinary alcohol works as well. If it is not 100% pure that is fine, as long as the only impurity is water. Denatured alcohol works too, just like other mixtures of alcohols. Baader's wonder liquid is an expensive example. Just as good as alcohol!

A complete lens cleaning kit would consist of a blower and a soft brush to remove any particulate matter, cotton and alcohol, and tissues.

Isopropyl alcohol is very mild. Ethanol/methanol slightly less so, but also safe.

Be careful with acetone - it cleans really well but dissolve plastics and you don't for instance want to smear the plastic of a lens retaining ring over your glass.

[ronin]

As you suspect they likely have an anti-fog component in the cleaning solution. Suppose not surprising in a way but maybe a little offputting. Shouldn't be a problem and it will wear off after a time. Guess it may be a film of something so if it bothers you then you can either leave it to wear away and then use something else in future or get a more specific cleaner that is known not to be anti-fog and use that to give them another clean in order to remove whatever is there at present.

Whatever it is, it sounds like the antifog bit of it works well.

[hjw]

The "anti-fog" agent in  your solution is most likely the surfactant. Surfactants are molecules with a hydrophilic (water loving) head and a hydrophobic (water repellent) tail. Glass is also hydrophilic and the surfactant will form what is called a "self-assembled monolayer", a layer (one molecule thick) with all the water repellent groups sticking out. The coat is very thin (a few nanometers) and will not affect the optical performance.

Clear skies

HJ

[Peter Drew]

I would leave things as they are, if they don't fog wnen you breathe on them then they are unlikely to dew up during night time use. 

[ImmortalBee]

Thanks for the info. That's put my mind at rest about it possibly having damaged my optics, plus any dew prevention effects will be very welcome! 

I already have a blower and a soft brush. The main items missing from my cleaning kit are solution and tissues/cloths to apply solution and wipe. I think I might pick up some of that Baader optical wonder fluid, its name pops up everywhere and never for the wrong reasons. As for tissues/cloths I used to have some good cleaning tissues which I picked up years ago, but I have recently misplaced them and had to start using microfibre cloths. I don't like the thought of reusing these cloths regularly but I've not decided on an alternative yet.

I think the most important step in keeping my binoculars clean however is to stop them getting dirty in the first place. Hopefully they don't get slammed objective first into the corner of the arm of a camping chair in the dark again...

[Dave In Vermont]

Methanol (Methyl Alcohol or Wood Alcohol) isn't recommended. Not that it will hurt the lens - it may hurt YOU! This stuff is very poisonous and can be inhaled, ingested, or enter through intact skin. Everything from terrible physical cramps, to blindness (sometimes permanent - depending on dosage), and death is possible.

I'd suggest avoiding this nasty stuff. I use 91% iso-Propanol which is available at most major pharmacies (chemists) over here.

Alcohols are highly flammable - leave the smokes indoors - try to work outdoors or in a well-ventilated area.

Dave

[ollypenrice]

You bought a commercial lens cleaning product and the binoculars are fine. You don't have a problem!

Olly

[Alien 13]

Binoculars and Camera lenses normally have very tough coatings and are better kept clean by whatever means, the real danger is locking them away in the dark with no fresh air especially if slightly damp.

Alan