oil immersion lens care

[bregalad]

I currently wipe over my oil immersion lens with a dry pec-pad tissue after use. The tissues are rather expensive and I'm just running out. What do other people do?

Do they do any cleaning? Some say it's not necessary with modern oils. Do people use a solvent? If so, what? And any particular tissue?

Grateful for any advice or comments.

[stickman]

Hi Bregalad

Nowadays I never bother cleaning mine - When I finish using the 'scope I make sure that I leave a slide on the stage and the lens is immersed in oil - so it always has oil on it and never dries out.

Cheers, Nick.

[Lancashire Lad]

Originally Posted by stickman

Hi Bregalad

Nowadays I never bother cleaning mine - When I finish using the 'scope I make sure that I leave a slide on the stage and the lens is immersed in oil - so it always has oil on it and never dries out.

Cheers, Nick.

Very useful tip!

I haven't dabbled with the immersion lens as yet but would be grateful if anyone could answer this question: -

Most of the "in depth" articles seem to suggest that in order to benefit from the the use of oil immersion objective lenses, the top lens of the sub-stage condenser should be "oiled" to the underside of the slide.

This seems like a step too far for me - as the condenser would then need to be scrupulously cleaned upon every change back to non-immersion objective lenses.

Does anyone actually oil the condenser lens as well? (and if so does it really make a visible difference to the resolution?) - or do you see still the benefit when just oiling the immersion objective itself?

Regards,
Mike.

[stickman]

Originally Posted by Lancashire Lad

Does anyone actually oil the condenser lens as well? (and if so does it really make a visible difference to the resolution?) - or do you see still the benefit when just oiling the immersion objective itself?

I've never heard of this before so I've just tried it out of curiosity!

Obviously the sub-stage condenser needs to be really near the slide to achieve a film between the two. This in iteslf (with my setup anyway) somewhat spoils the image by losing contrast.

Overall I found no real difference in image quality and as you say Mike, it's rather fiddly to clean.

Whilst on the subject, does anyone know if there's an odourless immersion oil available? The one I'm using stinks and I'm finding it difficult to identify certain agarics when all I can smell is the bloomin' oil....

Cheers, Nick.

[CorneliusMS]

Just for information, gentlemen . . .
Optimum function (max numerical aperture/max resolution) is obtained from oil immersion technique when both condenser and immersion objective are oiled, although improved function will be obtained if oiling the objective alone.
The condenser used is the normal type and does not need to be of any special 'immersion' type.
The specimen should also ideally be mounted using a medium with glass-compatible refractive index (~1.515).
This way, the light path from condenser right through to the objective is 'transparent' to each light ray and no refraction takes place.
Absolute, optimum resolution is only obtained by imaging with a single, filtered wavelength of light.
See:
Cargille - Immersion Oil and the Microscope
This link also discusses different types of oil (ideas for non-stinkiness?)

Chris

[bregalad]

Thanks for the useful link, Chris.

And thanks, Nick, for your suggestion of leaving the lens attached by oil to a slide. I'd have to remember to store the the microscope case upright though!

The oil I use seems to be odourless and suits me fine - it comes from Brunel. I did try an immersion oil from Scuddlebut, but it was too gooey (viscose?) for me.

But stinky? I used to love the smell of cedarwood oil in the morning ...

[Lancashire Lad]

Just used the oil immersion lens for the first time today. (and discovered that I've been missing so much by not having used it sooner. ).

Its use has given rise to the question - What to do with the oiled up coverslips at end of session?

With an eye on re-using them rather than just throwing them away, do any of you oil immersion regulars have any tips on best way of cleaning the oil off?- (which doesn't compromise/contaminate whatever specimen they would next be used with).

Regards,
Mike.

[fairplay]

I used to have this problem when I first started using an oil immersion.
Hopefully, these days immersion oil is no longer carcinogenic, but I used to place a teeny drop of Fairy Liquid on the coverslip, rub it in with my thumb or index finger, place under very slowly running water and this should then loosen the cover slip from the slide - this is when you have to be careful of any congo red or other stainers (esp. Melzers) getting on your skin.

Usually, I have a batch of about 6 slides waiting to be cleaned, so it's best to clean the surplus oil with a kitchen tissue first, then do the cleaning.

I still find it very tedious, and must say, off putting. You will find drying the coverslips even more tedious, and you will loose many and break many, and that is why these days I just throw them away.

There is a lady I know who simply re uses hers again and again by cleaning her slip with tissue immediately after the ID, but there is always the risk of contaminated material this way.

How do you manage cleaning the O.I. Lens itself ? I always use proper lens tissue, but no longer clean the lens at the end of the day - just once a week if using it regularly.
Be careful though not to use too much oil as the very first scope I bought had the retracting mechanism all gummed up presumably by oil creeping up the sides (previous owner - not me), and finally, don't ever make the mistake of lowering a non oil immersion lens into the oil pool - you will be rubbing the lens for ages to remove the oil before you have a clear picture again.

Neil.

[Lancashire Lad]

Hi Neil,

I generally wipe off the specimen with a dry tissue, then leave the used slides and coverslips soaking in plain water until I have about a dozen or so. I then use a plain warm water soak / flush / tissue drying method to clean them for re-use.

I’ve done that without any (apparent) problems ever since I got the microscope. I’ve only ever broken a couple of coverslips during washing / drying, so that hasn’t been a big problem.

The three coverslips I used with the oil immersion lens yesterday, I managed to clean reasonably easily by firstly wiping the oil off with a dry tissue, and then washing them in warm water with a few drops of washing up liquid added. I then left them soaking in plain water overnight, flushed them off, and dried them off earlier today – again with a dry tissue. It seems to have done a good enough job – although I haven’t yet used them again.

It seems a waste to throw them away, and I just thought that maybe there might be one or two good tips to be had for easily and thoroughly removing the oil.

Since posting yesterday, I found this site:-
http://www.memphys.sdu.dk/facilities...microscope.pdf - see page 9
which advocates the use of Acetone specifically for the removal of immersion oil from coverslips. – But using Acetone would bring its own health and safety issues, and I’m not too keen on that if there is a better safer method.

As far as cleaning the lens itself – well, I only used it for the first time yesterday, but I’ve adopted Nick’s approach and have left the scope set up with the oil immersion lens “parked” in a tiny drop of oil on a microslide on the stage.

Hopefully this will negate any need for cleaning the lens – or at least it should negate any frequent need for cleaning.
The scope is always left under dust cover, and I have never had any problems with dust – but if the oil ever does get contaminated then I’ll cross that bridge as and when. (I do have some proprietory “Whatman Lens Cleaning Tissues” from Brunel).

Regards,
Mike.

[flaxton]

For years I used to clean both slides and cover slips but no more. Once used they go into a jar of soapy water untill I have enough to fill an old slide projector rack which goes into the dishwasher (slides only). I found a supplier of cover slips at c£23 for a box of 2000 slips so they now get thrown out. Life is too short and they have lasted a few seasons so far.

Mal
Ps I also leave the lens in the oil