Cleaning the glass

robar · Joined: 25 Mar 2007 Posts: 90 Location: Dallas area, Texas

i've got a tamron SP 2x teleconverter. it had haze that did not look like fungus. i dismantled it and i've got all the glass clean and clear except for one lens. this lens is still foggy after several tries at cleaning with alcohol and acetone. it seems like the glass itself is foggy. does anyone know what the problem is?

LucisPictor · Expire: 2013-12-03

Hi!

I have talked to a vendor and shop owner I know, a very nice guy whom I really trust (he never tries to talk you into buying a lens, he gives honest advice).

He told me that mostly "haze" is water that has condensed at the surface of a glass inside the lens after it has been exposed to humidity.
He said, this wouldn't harm the lens at all (which really surprised me, since I thought it would cause immediate fungus) it just would reduce the contrast a little which would not be too bad if you shoot digitally.
When I asked him about possible fungus, he said that it could cause fungus but that it needed "some years" as long as the lens is not exposed to humidity and darkness again.
He also said that this kind of "misty" haze can easily be wiped away.
"Fungus" almost always showed some filaments, he said.

If you are not able to wipe it away, he also said, it would not simply be microscopic drops of water, but something that has permeated into the glass surface (very rare) or the coating.
This might be a consequence of fungus or might have another reason, it is not reversible, but again it does not influence the performance badly, unless it really turned the lens milky.

His final advice was to shoot with the lens and see if you can live with the results and and only do some cleaning if you are not satisfied and if you know what you are doing. The older a lens, he laughed, the easier it is to open it and get to the glass.

I guess, this does not help you a lot, I'm afraid, but it perhaps it consoles you a little... Wink

Attila · Expire: 2025-11-18

Yes I know I met sometimes glass is damaged you can't remove with any liquid. Perhaps a good try to bring the lens to an optician might be they are gently remove damaged surface. Try first with a cheap lens glass and look the result.

bob955i · Joined: 15 Apr 2007 Posts: 2495

I got a lens with a cloudy rear element that proved to be down to separation so I gently heated the element until it completely separated and then cleaned the balsam off. I then tentatively re-assembled the lens without re-cementing the elements - you can see Newton rings at certain angles but I intend to use the lens like this to see if the aberrations pose any problems in practice. If they do, I'll re-cement the parts.

The only thing I would say here is that the coating (where applicable) on the internal surfaces of lens elements sometimes isn't as durable as that on the outside so watch what you clean with should you decide to have a go.

Orio · Expire: 2012-12-04

robar · Joined: 25 Mar 2007 Posts: 90 Location: Dallas area, Texas

this is not water. taking the lens apart is a breeze, easy.
this is like either the glass or the coating is milky.
lucis, could you ask him if there is a way to remove the coating.

TIA

Attila · Expire: 2025-11-18

Good idea! Thanks for sharing!

Orio · Expire: 2012-12-04

LucisPictor · Expire: 2013-12-03

Next time, I talk to him I will ask, but I think that removing a coating will really damage the glass.

Orio mentioned a good point. The milky impression might derive from a vast number of tiny scratches...

robar · Joined: 25 Mar 2007 Posts: 90 Location: Dallas area, Texas

i checked. there's no cleaning marks. this is a totally enclosed internal lens.
roy

LucisPictor · Expire: 2013-12-03

OK, next thing that comes to my mind is that this is an element consisting of two lenses. These lenses are "glued" together with a special material and perhaps this glue has turned milky.

Orio · Expire: 2012-12-04

robar · Joined: 25 Mar 2007 Posts: 90 Location: Dallas area, Texas

this problem is the lens itself.
somebody is mailing me some cerium oxide to polish it with. hopefully i can do it evenly.
here's a temp fix and it works. ESPECIALLY on my polycarbonite eye glasses. just about any kind of wax will work.

I have a suggestion you might consider. Try spraying the etched
glass with "Lemon Pledge" and very lightly polish it off. An oculist
many years ago recommended that to me in lieu of the various (usually
unsuccessful) resin coatings touted to fill tiny scratches and other
surface imperfections on eyeglasses. He said that he used it
routinely on fine optical surfaces. I have been using it on my
eyeglasses regularly for perhaps 20 years and on filters for the last
several years. If it doesn't fix the problem, it washes off with
soap and water or isopropyl alcohol and you haven't risked anything.

Attila · Expire: 2025-11-18

Sound interesting I will try on my cheap damaged glasses.We have other furniture polish products here hopefully they do the job well. Let's try.

robar · Joined: 25 Mar 2007 Posts: 90 Location: Dallas area, Texas

i don't think i'll be trying to fix this lens. i just made another deal of the century. someone told me not to bother with it and he'd send me another for cost of post. he's a collector and said he had about 20 of them. i asked if by any chance he had a 140F 1.4x and a 200F 2x. he did and i picked them up for $90usd. both of these are matched TCs for the 300.
the 01F 2x is fairly common and is not the mathed TC. the 200F 2x is IMPOSSIBLE!! to find and a better match. i think there were under 3000 made and production ended in '84. the 140F 1.4x is still available but costly when one does emerge. i must be living right.