Confocal Microscopy List

Re: Cleaning lens.

Posted by Guy Cox on
URL: http://confocal-microscopy-list.275.s1.nabble.com/FW-Cleaning-lens-tp2567899p2568177.html

When I first learnt about microscopes (a very long time ago) I was taught that while dry objectives often had their front element mounted with some adhesive, oil immersion objectives didn't - the element was held by a screw ring. Hence it was safe to clean them with solvent - we usually used xylene because that was handy - it was also used in mounting specimens (with canada balsam). Of course this didn't offer any solution to the clumsy clot who gets oil on the x40. But that wasn't actually quite so common then because oil immersion lenses were longer - ie not parfocal - so if someone swung the turret round the dry lenses would clear the oil. On the other hand this didn't make using oil lenses too easy - and they didn't have spring noses then either.

Nowadays I'd have thought that if any adhesive is used it would be epoxy which is pretty much immune to solvents.

Guy

Optical Imaging Techniques in Cell Biology
by Guy Cox    CRC Press / Taylor & Francis
    http://www.guycox.com/optical.htm
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Associate Professor Guy Cox, MA, DPhil(Oxon)
Electron Microscope Unit, Madsen Building F09,
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From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Keith Morris
Sent: Wednesday, 1 April 2009 6:47 PM
To: [hidden email]
Subject: FW: Cleaning lens.

I think Zeiss’s comment that repeated use of ethanol will damage Zeiss’s lens cement was just that – use it a few times a day and the Zeiss objective will probably fail in 6 months or so [and this might be the case for many solvents, ethanol is simply one more readily at hand*]. Use ethanol every month or so and chances are the objective will last a lot longer [and fail for another reason]. Use ethanol on a very elderly microscope where the lenses are mounted in say gum resin though and you will destroy the objective pretty much instantly [or at least get a nasty smear of gum resin all over the clear bit] - hence some people’s historical aversion is justified. I did mention to a Zeiss rep why did he just use 70% ethanol on our new 100x zillion NA TIRF objective when Zeiss say that repeated use will damage the objective, he said, well repeated use will damage the objective, but once or twice won’t matter [and then I thought ‘well I suppose it’s not actually his £8,000 objective’]. Other manufacturer’s actually recommend ethanol, e.g. Olympus. However immersion oil doesn’t dissolve in ethanol that well, hence another reason for the recommended use of other solvents, e.g. Petroleum ether - see http://instrument-support.nikonusa.com/app/answers/detail/a_id/10379

*from the micro/primer site: "In the past, solvents have been routinely employed for nearly any cleaning task in microscopy, and particularly for removal of immersion oil. Potential problems associated with solvent cleaning are sufficiently serious that the best current approach in cleaning the microscope is to use solvents only when absolutely necessary, essentially as a last resort rather than a first step. The issue of the use of solvents is further complicated and confused by contradictory recommendations in the scientific literature, as well as by differences in manufacturers' technical publications. Although alcohol and xylene are widely recommended as lens cleaning solvents, they are also named as being harmful to both the mechanical and optical components of many microscopes. Because of the variation in solvent recommendations, and the likelihood that some of the materials used in the instrument components are not known to the user, it is prudent to restrict use of any solvent to an absolute minimum.”

i.e. have a look at: http://micro.magnet.fsu.edu/primer/anatomy/cleaning.html

Most of this discussion of solvents only applies to immersion oil objectives, where the oil isn’t miscible in water. Our inverted microscopes with all air objectives are rarely cleaned, otherwise it’s just a blow with a puffer. On microscopes where oil and air co-exist it’s often immersion oil contamination of the air objective that’s the problem, so it’s solvents again. In the days when only my group operated the microscopes, with all our oil immersion free upright microscopes the objectives almost never needed cleaning.

For other spillages such as culture medium [inverted microscope again] some solvents will probably fix biological muck onto the lens, and there’s the salts content, so the use of water based cleaners has been suggested [e.g. even breathing on the lens and then lens tissue, using optical/glass cleaning solutions]. Water drying onto the lens is a disaster though. Some even recommend things like breaking polystyrene foam [to get a clean surface] and gently rubbing the [oil free] lens with that. Or there’s Sparkle - whatever that is, here in the UK it was a silicon based furniture polish [yuk] not a commercial window glass cleaner. That’s the problem with industrial cleaners, who knows what’s in them or whether the constituents have been modified – you could try it on an inconspicuous area of the objective lens first, I suppose. Presumably optical lens cleaners are glass friendly though, and many use glass cleaning products with no reported problems. All the links in the previous posts [below] give loads of ideas for cleaning objectives [when necessary].

http://www.zeiss.com/C1256F8500454979/0/F9B766E00E70F4C4C1256F8D0054FFF8/$file/thecleanmicroscope.pdf

http://books.google.com/books?id=Dhn2KispfdQC&pg=PA51&lpg=PA51&dq=petroleum+spirit+cleaning+objectives&source=bl&ots=JxlHfCVuF5&sig=NTJt3Ol66sgsB8gluF1eKpeXLCc&hl=en&ei=DfvRSdGpI5WrjAflkvjlBg&sa=X&oi=book_result&resnum=1&ct=result

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artfeb04/cdclean.html

www.olympus.co.uk/microscopy/images/illum_cleaning.pdf
http://www.olympusmicro.com/primer/techniques/fluorescence/troubleshoot.html

Keith

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Dr Keith J. Morris,
Molecular Cytogenetics and Microscopy Core,
Laboratory 00/069 and 00/070,
The Wellcome Trust Centre for Human Genetics,
Roosevelt Drive,
Oxford OX3 7BN,
United Kingdom.

Telephone: +44 (0)1865 287568
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From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Chris Tully
Sent: 30 March 2009 16:40
To: [hidden email]
Subject: Re: Cleaning lens.

Dear all,

While working for a Leica Microsystems dealer the local field service engineer (factor trained) used a sequence of ethanol and heptane to clean truly dirty lenses. For standard cleaning a lens wipe and Sparkle was his recommendation. But for dried oil or the like he would graduate to cotton swabs and either ethanol then heptane or a 50:50 mix of the two.

Chris

Chris Tully
Microscopy and Image Analysis Expert
[hidden email]
240-888-1021
http://www.linkedin.com/in/christully

On Mon, Mar 30, 2009 at 10:12 AM, Ian Montgomery <[hidden email]> wrote:

Keith,

Methylated spirit that’s what he said, although I still prefer and use ether when necessary.

Ian.

Dr. Ian Montgomery,

Histotechnology,

I.B.L.S. Support Unit,

Thomson Building,

University of Glasgow,

Glasgow,

G12 8QQ.

From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Keith Morris
Sent: 30 March 2009 14:12

To: [hidden email]

Subject: Re: Cleaning lens.

Are you sure the Zeiss Engineer didn’t say ‘petroleum spirit’? Methylated spirit is mainly ethanol, and so best avoided - the Axiovert 100 manual says repeated use of 70% ethanol will damage the objectives [but you can use it if you want]. Generally the faster the solvent evaporation from the lens/cement area the better, hence the suggestion of the solvent [pure] diethyl ether by many [and that’s what I use].

‘Zeiss cleaning mixture L’, which the engineer’s now use since diethyl ether has been withdrawn from their kit, is 90% by volume ‘benzoline’ [petroleum ether sometimes called medical alcohol] and 10% ‘isopropanol’ [2-proponal, dimethyl carbinol, 2-hydroxyproparne]. The bottle says ‘Clean the optics by moving in circles, slight pressure should be exerted on optics during cleaning’. Petroleum ether or spirit isn’t the same as the diethyl ether solvent/anaesthetic often used to clean objectives, but apparently it does the job for Zeiss optics.

Keith

From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Ian Montgomery
Sent: 30 March 2009 12:28
To: [hidden email]
Subject: Cleaning lens.

In one of our teaching labs many years ago a student complained they were having a problem with the x100 OI objective and sure enough the image was lousy. I cleaned the objective and slide then re-applied a spot of oil and still the image was lousy. I then asked the student how exactly they had set up the microscope. Shock horror, my world collapsed. They had unscrewed the objective, filled it with oil, screwed it back on then put a drop on the slide. After weeks of trying to clean the objective it went into the trash as beyond economic repair.

Cleaning objectives, I use the fluid recommended by the local Zeiss engineer, 90% methylated spirit and 10% isopropanol.