in a cluster of micro algae. It was fixed with
Lactocupric and mounted in Glycerin
24 months ago. Rheinberg illumination (black center, clear green
illumination emphasizes the mastax trophi and the architecture of the
Click on the image to see it full size.
Pictures were taken at 640 X 480 with a Motic DC-3 camera, integrated in my National Optical Microscope, and reduced or cropped for their insertion in the article. Some pictures can be clicked on to see a bigger version. The width of the picture with each objective (on the pictures not cropped of course) is as follows: 4x = 3400, 10x = 1333, 40x = 340 and 100x = 133 microns. Equipment and the filters used were described in a previous article.
I wish to specially recognise the author of the small but splendid Neat Image Demo software, and to Jean Marie Cavanihac who brought it to my attention.
Due to the real concern about
risks associated with the
chemicals used in microscopy laboratories, I presented and
discussed in a
series of Micscape articles (see below) 20 safe mounting
20 formulas provide mounting mediums for all the materials which may be
of interest to the amateur. I present here a critical synopsis of the
than 20 months after first using the majority of them, and
my selection of the most useful ones.
Leaving apart the Damar Gum,
the mediums I review do not need any hydrocarbon solvents and therefore
have two main advantages:
1) they are safe, 2) they are cheap.
As I stated in my Conclusions
for the series: Leave the Canada Balsam for the professional
seek legitimately the “HYP”, (hundred years of permanence) for the
of their type species, and have many moments of recreation by making
collection of preparations look really professional.
Part 2. -
Simple drying mediums:
Part 3. - formulas: Fructoglycerol and modified Brun's medium:
PVA-lactic acid and PVA-glycerol
The gum arabic mediums
and 5. - The glycerin jellies and conclusions:
some inevitable repetition, my actual
on the use of those formulas is presented here..
Indicated when you want to
preserve for future
examination under the microscope your collections of micro
micro algae, mixed (or not) with very fine detritus. Fix them using 20%
20 or Lactocupric
added to your sample in the field. For a short term
examination you don’t need to wash the samples.
Try to obtain a very thin
Normally it is used for a provisional mounting
planned to last for weeks or some months at the maximum.
But because it
to be taken easily, and because the elasticity of the coverslip lets
and turn the individuals observed by applying light pressure with a
needle, it is one of the most useful techniques that the amateur must
are a very useful for the
rapid screening of a new
As you see, it is only a
refinement, but a
very useful one, of the wet-mount
method. By its nature, even well sealed, the duration of these
preparations is only two or three months. Because of this there are no
advantages of this technique are
shared by Glycerol, Fructose
or PVA-G (see below) employing in this case
a stepwise technique to
avoid the excess of osmotic pressure that these products can exert on
invertebrates, all very fragile, and obtaining with a supplementary
Glycerin is a difficult, but
permanent mounting medium. It
is also the standard to mount nematodes.
It exerts a great osmotic
living biological materials or
even on fixed but delicate ones, having as a result the distortion and
of the individuals. To avoid this it must be introduced very gradually.
The methods to do this were
discussed in the original article. With materials correctly fixed GP
guarantees an almost realistic aspect of the subjects.
pictures show micro-algae
some invertebrates mounted in glycerin. The sealing of the
coverslip must be
very carefully done. There
always the risk of infiltration. My
after 24 months has a bubble over almost ¼ surface of the slip.
Clearly 1) my
sealing was not perfect and 2) the materials were not in pure glycerin.
evaporated. But the remainder of the preparation provided splendid
the combined effect of lactocupric and glycerin. See later my
discussion of PVA-G.
MMF, Mounting mediums with Fructose
Pure, the fructose can be
found as a
powder in the sweeteners section of supermarkets. (If you bought a
kg), make donations to your colleagues, it will be sufficient for tens
and will last a long time.)
This can be
prepared according to the
formula of Larry Legg (see his article in Micscape).
Fructose is suitable for
(probably for fungi also) and for many of the invertebrates like small
entomostracans, or acarina.
more convenient and cheap,
is the concentrated corn syrup
(with 76% fructose) which is sold in the
My preparations are thin,
coverslips do not move, do not have
any crystallization, and even the
Gentian Violet stain is
Fructose receives subjects directly
from water, or
glycerin; if you have materials
preserved in alcohol, transfer them gradually to water. Like the
the fructose is capable of collapsing very sensitive materials. A
three or four stages can be necessary.
It receives and maintains
many dyes, and
preserves very well chlorophyll
in plant samples which were fixed with GALA or Lactocupric.
It is one of the easiest and
I think that Fructose
and PVA-G should be your
For handicrafts there
are sold some
transparent and syrupy glues made of PVA
Alcohol, not to be confused with Polyvinyl Acetate - also PVA - the
is the basis of students' glues) it can be bought in handicraft
and in my experience it is not difficult to find. The product is
and has the consistency of honey and can be diluted with 30% of water.
selected materials (you must test) can be mounted in this adhesive of 70%
PVA glue, directly from water or from a 1: 3 dilution of glycerol
water. The slides
must be sealed because if they are not, the pure adhesive tends to dry
and peels from the glass in a few months. I do not like the refractive
of the pure adhesive, the glycerin improves it a lot (see PVA-G).
You do not know the exact
of the prime materials, or
the exact concentration of the adhesives. But you are amateurs, and if
a tube of 50 ml of adhesive for one dollar, as I do, you would have PVA
your life (buy two if you anticipate a long time life.)
I encourage the search for this commercial adhesive because the PVA sold for microscopy is very expensive and difficult to obtain and dissolve. Glues are really very cheap and ready to use.
PVA-G. - Polyvinyl Alcohol with
and maintains the color
most usual dyes that the
amateur can employ, and also the chlorophyll of plants. And you can
in it practically all subjects, including pollen (with or without
am a fanatic of PVA-G and recommend that this becomes
difficult materials such as samples mixed with detritus,
which we discussed in the article on PG, a step by step method
can be used
with PVA-G with very good
results. This gives you a preparation
with the benefits (or better) of a glycerol mount, but solid, dry, and
easily and examined even with the oil immersion without problems. I use
product labeled "ITOYA" Paper Glue.
Some correspondents say that the PVA glues are difficult to find in
Water saturated with
polyvinyl product which
has 1% of phenol as
an included preservative; it is an
PVA-L. - Polyvinyl
alcohol with lactic acid.
This, and the now not
recommended GLG, were
proposed as a replacement for the formulation of Hoyer. Hoyer's
is a powerful clearing agent / mounting medium with arabic gum, chloral hydrate
forbidden. The lactic acid clears fast and is very penetrating,
formula was promising, but its refractive
index of 1.43, is
disappointing and much lower than that of
glycerin (1.47). The PVA-L is a good clearing medium
acts quickly, but if PVA-G is
allowed time, it must be more
the same materials. Of course, the preparations which I have, with PVA-L,
dry, firm, and clear. Certain materials like aphids cleared up
for example. But some of the slides had an additional problem which I
what to ascribe it to. They had small crystals strewn under the
reason which I can
discover that justifies this
fact and I believe simply that one needs to be very neat when one
washes the coverslips,
the slides, and also sourcing the fixatives or other reagents added to
For the moment I must
recommend the use of PVA-G, and to continue
some experiments with PVA-L. Here two successful examples of
picture is from a small
"thrip" (an insect of the order Thysanoptera) captured on a Gerbera jamesoni flower. It
was fixed with
alcohol 70%, washed in water and mounted with PVA-L, 8 months
is perfectly dry, firm and clear, without crystals. Notice the
particular wings of this insect. Obj. X10. Illumination through the
pictures were stitched for this image. The background was blurred
The common solvent for all
acetone, butyl acetate or many
other commercial solvents.
Generally, to employ it as
a mounting medium, it is wise to dilute it a
little with its solvent to make sure that it runs well under the
mounted leaf epidermis,
scales of butterfly, and parts of
insects, algae, protozoa and rotifers. The worst subjects were the
branches of filamentous algae, which were flattened by dehydration with
resin of vegetable origin, Damar shares with balsam the property
life. It is almost a HYP. Read the
its preparation and techniques for use in the previous article.
is naturally a very good choice, but
for the adult amateur. There
is a protozoologist who recommends it as the best medium to mount gregarines
(a form of parasitic protozoa).
II raised my objections to this much advocated medium in the previous article. Nothing has changed.
borax jelly is the most difficult formula,
although it is much
recommended (for pollen especially). Even with double borax and
disinfectant, this formula becomes easily soiled with fungi and
bacteria. I do
not use it.
See my comments and
techniques in the corresponding
Apathy was always blamed for the
crystallization of saccharose. In the very thin
preparations of tissues colored with
The formula does not dry
fast, but it
dries. The subjects included are
well preserved. The only problem is the crystals. Try to seal the
that GAF, which
incorporates fructose (I use Karo, see the
formulas), does not suffer the
crystallization problem. GAF
is my formula to replace the Lillie's
derived from Apathy’s
by incorporating fructose in
place of saccharose.
The results are comparable with PVA-G, even for the
protozoa. But the drying of the edges is much slower and in wet
require the assistance of a furnace. But it does dry.
But, before you engage in GAF preparation and its use, you must remember that the results are very similar and no better than mounting in fructose or in PVA-G. If you find Karo or fructose in your supermarket you do not need GAF. It is the same one if you obtain PVA.
I am not a diatomist.
But it is clear to me that this synopsis
must include this synthetic resin which has a refractive index of 1.58,
making it useful for the mounting of diatoms. It is sold to repair
lamp glasses of cars. Probably the cyanoacrylate resins which must be
(the intense indirect light of the sun is a good source of UV) could
or less the same index. I never have used it but it is frequently
AG, alcoholic glycerol
GLG, arabic gum, lactic acid
FJ, Fructose Jelly
They all have a good
for short term work. But they
do not harden at all, they need to be very carefully sealed, and by no
they better than those discussed above. I’ve discarded their use.
Thus, you have a useful and
required medium for temporary mounts: Aw.
mediums of choice for the average amateur: FMM (home made solution of
fructose, or preferably commercial fructose syrup of the Karo type), PVA-G, NPM, and the Kaiser’s Jelly. And a medium
for adults: Gum Damar.
can not find fructose or PVA, use the very good but a little more
difficult GAF. Two good
mediums: PVA-L, for a
similar result to the PVA-G; PG,
to seal, for certain subjects it is similar to PVA-G, (for the moment
be considered the standard for the nematodes, in the future we must
with the PVA-G or the PVA-L). We
also have a special medium for diatomists: Norland 61. So the present review reduces
the list of
the most useful
amateurs' safe mounting mediums from twenty to nine (postponing my opinion
on PVA-L pending additional experiments).
Marcel Lecomte site http://users.skynet.be/Champignons_passion/main.htm
Jean Legrand CONSTRUCTION D'UNE HOTTE DE SECHAGE http://www.microscopies.com/DOSSIERS/Magazine/Articles/JLegrand-Hotte/Etuve.htm
Please report any Web problems or offer general comments to the Micscape Editor.
is the on-line monthly
magazine of the Microscopy
site at Microscopy-UK