Windex.
Larry
Joe Gwinn wrote:
> Brian,
>
> At 5:18 PM +0000 1/29/02, olympus-digest wrote:
> >Date: Wed, 30 Jan 2002 00:11:57 +1300
> >From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
> >Subject: [OM] Cleaning lenses
> >
> >Hello folks,
> >
> >Can I ask for a bit of advice? (of course)
> >
> >I just got a lens back from having fungus removed - as much as he could get
> >at. The lens is a Mamiya Press 100mm, and the front element is screwed on
> >very tight.
> >
> >The rear lens element lives in a huge cavern surrounded by helicoid threads
> >etc.. I noticed that the outside surface is covered in a kind of oily film
> >that
> >you don't see by looking at the lens surface with reflected light, but if the
> >lens is opened up and a light shines through, it is very obvious.
> >
> >I tried removing this by huffing on the element and wiping with Oly lens
> >paper, but that really didn't work. The muck just spread around a bit more.
> >It
> >needs an organic solvent. It's go to go - it surely acts like a soft-filter
> >and I
> >don't want that. The 100 has a reputation of being a sharp lens and that's
> >why I bought it - to yield sharp images.
> >
> >I wonder if the iso-propanol that is used for cleaning tape recorder and
> >video
> >heads would do the job without damaging the lens. I think it should - but am
> >I
> >correct?
>
> I would first use denatured alcohol, as was suggested by another poster. One
> can buy 99% Isopropyl Alcohol at drug stores, but denatured alcohol is more
> aggressive, and can be obtained at hardware and paint stores by the gallon.
> Neither will remove paint, such as the anti-reflection black paint used
> inside lenses.
>
> By the way, I've had good luck using alcohol to remove fungus.
>
> If alcohol fails, I would use Acetone or Methyl Ethyl Ketone, which are also
> available at hardware stores and paint stores by the gallon. These are more
> aggressive than alcohol, but will affect paint, so use a damp (not wet)
> wooden-handled Q-tip and be careful. If the oil film is significant, it's
> probably a good trade to live with some loss of paint around the lens.
>
> The next step up is Toluol, available in some pait stores.
>
> If the film resists Acetone and MEK and toluol, which can happen if the oil
> film has cured like paint, paint stripper is needed. I would very carefully
> use a Methylene-Chloride based stripper such as 5F5, applied and removed with
> a Q-Tip. Use the prior solvents to remove the traces of 5F5.
>
> An alternative approach is to use pure Methylene Chloride, which can be
> obtained by the gallon from plastics supply houses (used to solvent-weld
> plexiglas), and by the expensive half-ounce from model shops (used to thin
> Testor's paint).
>
> I would *not* use a lye-based paint stripper. Lye will etch aluminium, and
> may strip the anti-reflection coatings as well. And, it's hard to get all
> the residue off, and that residue will likely cause corrosion. How to tell?
> Read the health warnings. It should complain only of Methylene Chloride (and
> Methyl Alcohol) and should not warn of Sodium or Potassium Hydroxide, or
> anything else..
>
> These solvents will not affect lens coatings, but be very gentle with the
> Q-Tips.
>
> Joe Gwinn
>
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