The masses (or at least Giles and Mahlon ;) have spoken. Here it is.
Actually, I wasn't being a slacker, I was just waiting until we cleaned
our 24" to see how the stuff worked there. Enjoy!
Cheers,
--Lee
Review of Opticlean Polymer
By
R. Lee Hawkins
Whitin Observatory
Wellesley College
Opticlean is a polymer that you brush onto optics, allow to
cure, and then remove with sticky-backed "pull tabs" that look
suspiciously like mailing labels. It is used for cleaning both lenses
and mirrors (coated or uncoated). It is available from Dantronix
(www.opticlean.com).
I, like many of you, was thrilled when I first heard of
Opticlean Polymer. This magical polymer, which you brush onto your
optics, allow to dry, then peal off is advertised as leaving optics
"molecularly clean". While I have found it useful in cleaning optics,
it does have limitations, which I'll outline below. In most of the
tests below, I purposely put lots of greasy fingerprints on the optics
before cleaning them (but didn't allow the fingerprints to harden).
My first day of testing Opticlean was a dismal failure. I tried
the solution on 3 different optics: a Meade corrector plate, an old wide
angle Nikon lens, and a Zuiko 50/1.8. On the Meade, I had lots of
problems with the film tearing on removal, and leaving little patches of
Opticlean behind. On the Nikon (which has a fairly flat front element),
it seemed to work fine, but didn't clean off some old water spots. On
the much more steeply curved Zuiko, I had major problems getting the
Opticlean to come off at all. Needless to say, this experience left me
wondering if Opticlean was really all that it was advertised to be.
The following day, I contacted Jim Hamilton of Dantronix, the US
distributor of Opticlean, and he gave me some good hints to solve the
problems I was having. First, my coats of Opticlean were too thin,
leaving a film that was weaker than the film's bond to the optic.
Secondly, I was waiting for the recommended 2-5 minutes for the polymer
to cure, thinking that if I waited longer the polymer would set on the
optics and be difficult or impossible to remove. It turns out that just
the opposite is true: as Opticlean cures, it shrinks, and the bond to
the optic weakens somewhat. Jim indicated that for large optics with
thick coats, more time was necessary. Finally, Jim reports that
Opticlean cannot deal with such things as dried and hardened water
spots, very old finger prints, and the like. Those have to be softened
first with methanol or some other solvent.
This brings us to my second day of testing Opticlean. My
results on the Meades were much better. I both put on a thicker coat
and allowed the polymer to dry for about 30 minutes before pealing it
off. However, I still had problems with small patches being left behind
where I wasn't careful enough to get the coating on uniformly. Also,
Opticlean still didn't get my corrector plates "as new" clean. Dried
condensation is the bane of my existence here in the East US, and dried
condensation tends to "glue" small particles to optics when it dries.
The best way to remove these particles (and any small patches of
Opticlean left behind) is with Eclipse lens cleaner and
PEC-Pads.
Next, I tried Opticlean on the edge of a 60+ year old front
surface mirror that is in the optical path of our spectrohelioscope.
This mirror has a hazy film on it, which I was hoping Opticlean would
remove. While I didn't have any problems this time with little spots
being left behind, Opticlean also did nothing to remove the hazy film!
The area I cleaned was indistinguishable from the surrounding area.
Once again, it was Eclipse lens cleaner to the rescue, and now the mirror
is bright and shiny.
Finally, I revisited the Zuiko lens. This time, with a thicker
coat of Opticlean and a longer curing time, I had no trouble removing
980f the polymer, but there were still a few spots that remained.
These results prompted further discussions with Jim, and we
determined that perhaps I had a bad batch. He sent me a replacement
kit, and on trying it with the Meades, I had much better luck. A thick
coat kept the polymer from tearing on removal, and I had none of the
problems described above.
Finally, I used Opticlean as part of a 3-step process to clean
our 24" mirror. This time, I used a 1" paintbrush to spread the
Opticlean (we bought a pint for this larger area), used a thick coat,
and allowed it to cure for about 2 hours. On this larger optic, with
only one coat, I did have problems with patches that didn't come off.
It was also much easier to see why on the larger optic. If the
thickness of the coat is not controlled pretty well, you get thin spots
which are weaker than the surrounding film, and they tend to tear out.
After speaking with Jim some more, and thinking about what was going on
myself, I have come to the conclusion that 3 thin coats (or even more
for large optics) are much better than one thick coat. Using several
thinner coats tends to even out weak spots in the polymer.
What are my conclusions? Well, in all cases Opticlean removed
the larger gunk and fingerprints perfectly. It also removed some sticky
stuff from one of the pull tabs that I inadvertently got on the Zuiko,
so it is a useful tool in your cleaning supplies. However, it won't
remove particles glued on by condensation, spots caused by condensation,
or old finger prints. Thus, I see Opticlean as part of a two-step
process in cleaning our optics here at the Observatory. I first use
Opticlean to remove all the big stuff that would tend to scratch the
optics, then use Eclipse cleaner and PEC-Pads from Photographic
Solutions (www.photosol.com) to bring the optics to as-new condition.
Finally, for optics over about 4-5" in diameter, I suggest you get some
of the larger pull tabs from Dantronix (supposedly "bumper sticker size")
and use them as is or cut them down so that you have the pull tab
supporting the film as you remove it. I think this would have resulted
in fewer left-behind spots when I was cleaning our Meades and the 24".
I also wonder if putting a layer of cheesecloth between to layers of
Opticlean would work better than the pull tabs for removing the cured
polymer.
Final word: Is it worth $95 for the kit? My answer is a guarded
"yes". Opticlean will remove big gunk that would tend to cause you to
scratch your optics if cleaning them in a conventional manner, but if
you want pristine optics, you're still going to have to use some sort of
lens cleaner. Based on my experience, the $95 kit will clean an 8" Meade
corrector plate perhaps 6 times for each of the two larger bottles in the kit.
This translates to a *lot* of 35mm camera lenses, and there is a smaller
nail-polish like bottle of Opticlean in the kit that probably contains
sufficient polymer to clean an 8" Meade corrector plate another 3-4 times.
If Opticlean saves you from scratching your optics, it is definitely
worth it. With that said, I've been cleaning astronomical optics and
camera lenses for about 15 years, none of it with Opticlean, and I've
seldom scratched or sleeked an optic. As with any method, you have to
be careful when cleaning optics with Opticlean, and understand its
limitations. There are no "magical" cures (no pun intended :).
For more quantitative tests of Opticlean by ESO on their 8-m VLT
mirrors see _Reflecting Telescope Optics Volume 2_ by R.N. Wilson.
Available from Springer-Verlag (www.springer-ny.com in the US). The
gist of the tests was that Opticlean brought the reflectivity of a dirty
mirror back to almost the same as a new coating.
Cheers,
--Lee
(By the way, Step 1 in cleaning big optics for us is a C02 "Snowclean
Machine" which gets rid of any loose dust before Opticlean is used. As
these cost over $1000 without a cylinder of C02, I doubt many camera
buffs will find them worth it).
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