So today I'm going to talk about how to clean microscope
optics, and in particular, how to clean objectives and
optical filters. And this is something that is an important
technique to know because it's pretty easy to get optics
dirty. Particularly if you're using oil immersion objectives,
as you tend to accumulate old oil on the objectives, you can also
smear oil on air objectives that aren't supposed to have oil on them.
Those are probably the two major sources of dirt that we
see here. Before you go to clean your objectives, it's best to
check the manufacturer's recommendations. Different manufacturers
recommend different methods of cleaning their objectives.
In particular, different solvents or cleaning products to use.
So what I'm going to recommend here, what we like to use
for our Nikon objectives, but if you have a different microscope
you may want to be using some other cleaning product.
So the first thing to do is to inspect your objectives and
see if they need cleaning. So we can take off an objective
from the scope here. And then take a look at it. And the first
step is just to inspect it by eye, you can look at it and see
if it looks like it's dirty. You can look through it, to see if
you get a good clear image through it. It's hard to do this
with these high magnification objectives, but for low
mag objectives, looking through them is an easy way to spot
dirt. And then for these high mag objectives which have these
small lenses, one useful technique is that you can pull off
the eyepiece of the microscope. And if you look through
them backwards, they make a very good magnifying glass, so you
can use that then to get a close up inspection of the front element
of this objective, and see if it's got oil or dirt or debris on it.
So to clean this, I'm going to put it down on the table,
get a piece of lens paper here, and then peel off a single sheet
of lens paper, being careful to only handle it by the edges,
not by the center because I don't want to get fingerprints
and oil from my fingers onto the objective.
So you take your lens paper, handling it by the edges, and then
the way I like to clean objectives, these Nikon objectives, is using
xylene or chloroform to remove the oil, followed by methanol
for cleaning up any residue left behind by those solvents.
And in all cases, I use the spectrophotometric grade
solvents. So to clean this, you put the lens paper down on
the objective, take your solvent here, and then put a single
drop on the objective, and then pull the lens paper gently
from side to side, so that you wick off the solvent, along with
any dirt on the objective. You can take a look at it in between
and see that this is now much cleaner. And then I'll just repeat
with methanol. And that's how you clean an objective.
For objectives like this air lens here, where the front element
is recessed, the lens paper trick doesn't work so well
because it doesn't get into the concave part of the lens.
And so for those, I like to use cotton swabs, you can either buy
commercial cotton swabs, the glue-free ones are best.
Or you can make your own just by taking pure cotton and twirling
a little wooden stick in it to pick it up. But otherwise the cleaning
procedure is the same, we're just going to use a swab instead
of lens paper. So again, I'll wet my swab with solvent
and then just go in here and gently swipe across the surface
of the lens, using a new surface of the cotton swab each time.
And again, I would repeat with methanol to remove any residue
from the xylene, until that objective is clean.
For air objectives, if they don't have oil on them
you also want to use a blower on them to remove any loose dust
so that you don't scratch the objective. If the objective
is oily, this is not terribly helpful because the oil will stick
the dust in place. But if it's not, it's generally a good practice
to use a blower like this one to blow off any loose dust on
the surface of the objective. Another useful way of detecting
these, in addition to looking at them with a magnifier
is also you can look through the objective at a distant object
and see if there's blur or dirt, which you can see if the streaks
or aberrations in the image. That works better for low magnification
objectives, than high magnification ones. So that's the basics
of cleaning objectives, it's good practice to do this routinely.
Particularly for oil objectives, which tend to build up residue
and gunk. One other point worth bearing in mind is that
these solvents that we're using here are really designed
for removing oil from objectives. If your objective has
been dirtied with say, tissue culture media or some other
water-based substance, then you'll want to use water,
maybe with a little bit of soap in it to remove that residue
and then follow up with distilled water and methanol,
probably to get the cleanest lens. Some manufacturers also
recommend using Sparkle window cleaner, or they have custom
cleaning products you can use for their objectives.
So now I want to talk about cleaning the filters and we're
going to talk about cleaning two different kinds of filters.
So here we have a filter that's mounted, you can see it's mounted
with this black ring. And we'll want to clean this slightly differently
than an unmounted filter. So let me get a piece of lens paper to put
these on. So again, we use lens paper here to avoid
getting dirty. So there's a mounted filter, which is mounted
in this metal ring. Here's an unmounted filter now, which
doesn't have that ring around it. It's just a piece of glass.
This, you want to be especially careful because putting it
down, there's no metal ring for it to rest on.
For the unmounted filter here, we can use the same lens paper
trick we used for the objective. First, I want to blow it off
and remove any loose dust here. So clean off the dust,
and now we'll take a piece of lens paper, again handling
by the edges. And then, use a little stick here and put a drop
of solvent on the optic. And then again, do this drag mopping
technique to gently drag the solvent off, pulling any dirt
with it. And the stick is here just to keep the lens, or the uh
filter from sliding around as I do that. That technique does not
work on these mounted filters because you can't get
the lens paper in close contact with the filter everywhere.
So here again, we're going to use cotton swabs. Again,
blow off any dust so we don't scratch it with dust on it.
Then, put it down on our lens paper. Take a clean swab,
you always want to use a clean cotton swab, so you don't
transfer dirt from one optic to another. Moisten it with solvent,
and then gently, using a spiral motion, clean it from the center
to the outside. Just removing any residue or dirt on there.
And that's how you clean a filter.