Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
Cleaning spectrophotometer mirrors?
402 views
Skip to first unread message
gr
May 19, 2012, 12:39:53 AM5/19/12
to
I am working on a Cary 5 spectrophotometer which seems to have low
energy. The spinning mirror and first lamphouse mirror are quite covered
in what looks like fine hazy dust. I have been told to clean the first
mirror, and the spinning mirror looks bad enough I think it needs
cleaning also.
I have some cotton wool as well as reagent grade acetone, iso-alcohol,
and methyl alcohol on order.
Will I be safe enough(and clean enough)with very very gentle wiping? I
know I am not supposed to touch gratings at all, but are other mirrors
ok for this treatment?
Any info on technique appreciated!
energy. The spinning mirror and first lamphouse mirror are quite covered
in what looks like fine hazy dust. I have been told to clean the first
mirror, and the spinning mirror looks bad enough I think it needs
cleaning also.
I have some cotton wool as well as reagent grade acetone, iso-alcohol,
and methyl alcohol on order.
Will I be safe enough(and clean enough)with very very gentle wiping? I
know I am not supposed to touch gratings at all, but are other mirrors
ok for this treatment?
Any info on technique appreciated!
anorton
May 19, 2012, 3:28:24 AM5/19/12
to
"gr" <greif1no...@rochester.rr.com> wrote in message
news:4fb7241c$0$26562$c3e8da3$14a0...@news.astraweb.com...
off the bat, there may be hard particles that will scratch the surface.
Probably the safest thing (and most expensive) is to use this stuff:
http://www.photoniccleaning.com/
Otherwise, assuming you can not remove the mirrors, you can first brush with
a very soft artists brush to remove any hard particles.
After this there are a variety of techniques and everybody uses a different
one. Some use cotton and solvent, but I find that usually leaves streaks.
Some use a single thickness of wetted lens tissue dragged slowly across the
surface with no pressure, but I find that does not remove tenacious dirt. I
prefer to use the rounded edge of lens tissue that has been folded a couple
of times along with light pressure. Even better is a soft polyester
cleanroom wipe.
Whichever method, a very grungy surface will need more than one pass. It may
even need water on the first pass followed by solvent on the second to get
everything off. Water removes some minerals and proteins that alcohol and
acetone do not, but it will always leave streaks that must be removed on the
second pass.
The most important trick to avoid streaks is to wipe slowly enough that the
solvent is evaporating off the trailing edge faster than you are wiping.
Keep a nice straight flat edge in contact with the glass - no wrinkles. The
first wipe should be done VERY gently just in case any sharp particles
remain. Wear solvent resistant gloves (NOT latex or vinyl) to keep the
optics clean.
As for the solvent to use, there is a superstition circulating that alcohol
is not good for overcoated aluminum mirrors. I have never found any hard
evidence to back this up, and I have never seen any degradation caused by
cleaning with alcohol myself. If any one here has any hard data on this one
way or another, I would appreciate it. Acetone will also work fine. It
evaporates more quickly, so it allows you to wipe more quickly. Do not
leave you solvent containers open for very long. They will both absorb water
out of the atmosphere which will make it harder to avoid streaks. A lot of
people love methanol for cleaning as it does very good job removing grease
but it can be corrosive to bare metals. Also keep the solvent away from any
paint on the mirror mounts.
After all of this you may find the problem is actually with the coating
itself which can be damaged by being coated with crud for years. UV light,
as you might find in a spectrophotometer, is also notorious for damaging
coatings.
--
Adam Norton
Norton Engineered Optics
www.nortonoptics.com
(Remove antispam feature before replying)
Ron Gibbs
May 19, 2012, 5:35:08 AM5/19/12
to
"anorton" wrote in message
news:6fudnTGJsZM81irS...@earthlink.com...
on to discuss for hours (the other is black finishes). This is as good a
description of practical cleaning technique on mounted optics as I have
seen. I hope everyone noted the implicit caveats & warnings - it really is
not easy. The only general point I would add is that mounts usually really
get in the way (maybe not in the OP's system?). You need to be able to wipe
over the edges. My advice to service engineers who ask about how to clean
mounted optics was "don't do it!". Often, cleaning makes the system worse.
Ron
www.gibbsassociates.co.uk
Helpful person
May 19, 2012, 6:16:44 AM5/19/12
to
On May 19, 12:28 am, "anorton" <anor...@removethis.ix.netcom.com>
wrote:
> "gr" <greif1nospamh...@rochester.rr.com> wrote in message
>
> news:4fb7241c$0$26562$c3e8da3$14a0...@news.astraweb.com...
>
>
Excellent post, thank you. Everything stated is of value.
I would just add a few comments.
The camel hair brush is an excellent way to remove particles. Brushes
are available with as few as one hair which with a magnifier can be
used to easily remove particles. (At least the ones you can see.)
Compressed air can also work, but only if ionized to remove static
electrical build up. Cans of compressed air are worse than useless
because they will charge the surface which then acts as a dust magnet.
In my experience a really dirty optic that is still in its mount is
almost impossible to clean.
Acetone will dissolve many optical cements. So be careful how it is
used.
I also have a question. Has anyone successfully used an ultrasonic
bath to clean dirty optics?
http://www.richardfisher.com
wrote:
> "gr" <greif1nospamh...@rochester.rr.com> wrote in message
>
> news:4fb7241c$0$26562$c3e8da3$14a0...@news.astraweb.com...
>
>
I would just add a few comments.
The camel hair brush is an excellent way to remove particles. Brushes
are available with as few as one hair which with a magnifier can be
used to easily remove particles. (At least the ones you can see.)
Compressed air can also work, but only if ionized to remove static
electrical build up. Cans of compressed air are worse than useless
because they will charge the surface which then acts as a dust magnet.
In my experience a really dirty optic that is still in its mount is
almost impossible to clean.
Acetone will dissolve many optical cements. So be careful how it is
used.
I also have a question. Has anyone successfully used an ultrasonic
bath to clean dirty optics?
http://www.richardfisher.com
Phil Hobbs
May 19, 2012, 10:23:02 AM5/19/12
to
for years. You have to be very careful not to let the optical surfaces
touch anything in the bath, though!
A rinse with water plus detergent, ideally with a reasonably high
pressure spray, gets rid of many particles without giving them a chance
to gouge up the surface. Scattered light tends to be more nearly
proportional to the perimeter of an object than to its area, so
exchanging a big particle for a fine scratch usually is not a win.
My favourite detergent is Triton X-100 from Fisher Scientific. Highly
effective in very small quantities, very gentle, and doesn't leave a
residue after rinsing.
I generally prefer a clean chamois leather to lens paper. It embeds
particles much better, has zero abrasive action itself, and seems to do
a much better job on films as well. You can get it inexpensively from
McMaster-Carr, and use it on your eyeglasses as well.
The lens-paper-dragging method is what is generally recommended for
doing laser Brewster windows, and it works fine for that. I don't know
about using it on coatings.
And do use electronic-grade solvent, not the stuff from Home Depot.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Joseph Gwinn
May 19, 2012, 12:16:52 PM5/19/12
to
In article <jp7pg6$7kv$1...@speranza.aioe.org>,
See "Other Uses" in <http://en.wikipedia.org/wiki/Collodion>.
One can still buy USP Collodion (flexible), but the USP kind isn't cheap
<http://www.sciencelab.com/page/S/PVAR/SLC1921>. It's about the same
price as the Photonic Cleaning stuff.
So, here's a much cheaper source, used for stage makeup:
<http://www.amazon.com/0129-1-Collodion-Flexible-Liquid-Chemical/dp/B004Y
NOX7U>. It may have lanolin in it, or the like. If so, there would be
a second step, where grease is removed with solvent.
Joe Gwinn
"Ron Gibbs" <r...@gibbsassociates.co.uk> wrote:
> "anorton" wrote in message
> news:6fudnTGJsZM81irS...@earthlink.com...
>
>
> "gr" <greif1no...@rochester.rr.com> wrote in message
> news:4fb7241c$0$26562$c3e8da3$14a0...@news.astraweb.com...
> >I am working on a Cary 5 spectrophotometer which seems to have low energy.
> >The spinning mirror and first lamphouse mirror are quite covered in what
> >looks like fine hazy dust. I have been told to clean the first mirror, and
> >the spinning mirror looks bad enough I think it needs cleaning also.
> >
> > I have some cotton wool as well as reagent grade acetone, iso-alcohol, and
> > methyl alcohol on order.
> >
> > Will I be safe enough(and clean enough)with very very gentle wiping? I
> > know I am not supposed to touch gratings at all, but are other mirrors ok
> > for this treatment?
> >
> > Any info on technique appreciated!
>
> The problem with a really grungy mirror is if you try to just wipe it right
> off the bat, there may be hard particles that will scratch the surface.
> Probably the safest thing (and most expensive) is to use this stuff:
> <http://www.photoniccleaning.com>
This is an update of the old collodion-film approach to cleaning optics.
> "anorton" wrote in message
> news:6fudnTGJsZM81irS...@earthlink.com...
>
>
> "gr" <greif1no...@rochester.rr.com> wrote in message
> news:4fb7241c$0$26562$c3e8da3$14a0...@news.astraweb.com...
> >I am working on a Cary 5 spectrophotometer which seems to have low energy.
> >The spinning mirror and first lamphouse mirror are quite covered in what
> >looks like fine hazy dust. I have been told to clean the first mirror, and
> >the spinning mirror looks bad enough I think it needs cleaning also.
> >
> > I have some cotton wool as well as reagent grade acetone, iso-alcohol, and
> > methyl alcohol on order.
> >
> > Will I be safe enough(and clean enough)with very very gentle wiping? I
> > know I am not supposed to touch gratings at all, but are other mirrors ok
> > for this treatment?
> >
> > Any info on technique appreciated!
>
> The problem with a really grungy mirror is if you try to just wipe it right
> off the bat, there may be hard particles that will scratch the surface.
> Probably the safest thing (and most expensive) is to use this stuff:
> <http://www.photoniccleaning.com>
See "Other Uses" in <http://en.wikipedia.org/wiki/Collodion>.
One can still buy USP Collodion (flexible), but the USP kind isn't cheap
<http://www.sciencelab.com/page/S/PVAR/SLC1921>. It's about the same
price as the Photonic Cleaning stuff.
So, here's a much cheaper source, used for stage makeup:
<http://www.amazon.com/0129-1-Collodion-Flexible-Liquid-Chemical/dp/B004Y
NOX7U>. It may have lanolin in it, or the like. If so, there would be
a second step, where grease is removed with solvent.
Joe Gwinn
Ron Gibbs
May 19, 2012, 2:02:11 PM5/19/12
to
"Helpful person" wrote in message
news:754faea0-aebf-4c88...@pa10g2000pbc.googlegroups.com...
>I also have a question. Has anyone successfully used an ultrasonic
>bath to clean dirty optics?
>http://www.richardfisher.com
unless the exact nature of "dirty" is known, no one single process is
guaranteed to give a clean surface. Generally, gentle brushing, then
water/detergent followed by organic solvent of choice is a good strategy.
Ron
www.gibbsassociates.co.uk
Ron Gibbs
May 19, 2012, 2:08:16 PM5/19/12
to
"Phil Hobbs" wrote in message
news:faidndTg5PlHMSrS...@supernews.com...
>I generally prefer a clean chamois leather to lens paper. It embeds
>particles much better, has zero abrasive action itself, and seems to do a
>much better job on films as well. You can get it inexpensively from
>McMaster-Carr, and use it on your eyeglasses as well.
>The lens-paper-dragging method is what is generally recommended for doing
>laser Brewster windows, and it works fine for that. I don't know about
>using it on coatings.
optics, as it contains silicone, which is OK in visible, but absorbs in IR.
Ron
www.gibbsassociates.co.uk
anorton
May 19, 2012, 7:53:07 PM5/19/12
to
"Ron Gibbs" <r...@gibbsassociates.co.uk> wrote in message
news:jp8ni8$iau$1...@speranza.aioe.org...
eyeglasses. I would not use that on precision optics in any case. The are
lots of varieties of lens paper that are better suited for precision optics.
Some are softer than others. Berkshire makes some good stuff (
http://berkshire.com/products/27-optics ). I have some of their LENSX 90.
I am also using a brick of 500 sheets of Navy surplus lens paper I got on
ebay. Each booklet has 25 sheet of thick absorbent paper and 25 sheet of
very thin soft paper. Paper that is crinkly does not work well for
cleaning. As I mentioned earlier I also like the soft clean room cloths.
I imagine they respond much like a leather chamois. I think if I used a
natural chamois, I would want to make sure it was cleaned very, very well.
As others mentioned, if the optic can be removed and immersed, often the
best method is to wash in mild detergent solution, rinse in DI wafer and
blow dry with clean, dry compressed air or nitrogen.
gr
May 19, 2012, 10:58:09 PM5/19/12
to
spectrophotometer cannot be removed, so major flushing is out. I can now
follow the best "generally accepted cleaning methods"!
Helpful person
May 20, 2012, 12:28:54 PM5/20/12
to
suggest you do not try to clean them. I expect the chance of making
them worse is much greater than improving the situation. If this is
not acceptable try and find someone close by who can help.
http://www.richardfisher.com
0 new messages