as a Substitute for Hoyer's Solution Mountan - Revisited
Glycerin Jelly as a Substitute for Hoyer's Solution Mountant - Revisited
The previous page on Glycerin Jelly was apparently rather well perused, and this is a simplified summary of the important items on that page.†
How to make Glycerin Jelly
Take 2 packets (2 time 7 g) of gelatin (Knox brand works fine),
Mix in 50 ml cold water to hydrate,
Heat but don't boil while still stirring, until the liquid is clear or at least there are no undissolved gelatin,
Swirl it to dissolve all gelatin,
Add glycerin to 200 ml,
[Optional: Add a crystal of thymol to keep down bacteria and fungi,]
Heat for about an hour until dissolves and the liquid is clear,
Pour on a clean PVC (polyvinyl chloride) pan with a flat bottom to make a thin layer,
Leave uncovered (drape a cloth if dusty) overnight or a couple days to allow most water to evaporate,
Peel off the thin, flat sheet of glycerin jelly,
Roll into a kind of jelly roll,
Slice the roll crosswise into neat, tight curlicues or helixes about 1/4 inch wide,
Keep in a plastic box,
Pinch off a small piece when wanted.
If there are bubbles, reheat in a beaker (water bath is helpful) and let stand as liquid. Do not keep hot for a very long time, as heat denatures the gelatin.
The glycerin jelly will be hard to remove from the plate unless the water portion has evaporated. It is best to evaporate the water portion with heat since glycerin absorbs water, to some extent, from the air.
Why use Glycerin Jelly?
Problems arise when microscope slides are made, as is commonly the case in bryology, with Hoyer's Solution. The slides remain sticky too long and arrive through the mail smeared. Also, some researchers may not have access to Hoyer's Solution as a mounting medium because a main ingredient, chloral hydrate, is a controlled substance.
You can make an acceptable mounting medium with glycerin jelly.
How to use Glycerin Jelly
Put your plant material on a slide in water, soak, maybe heat a little with a butane cigarette lighter until well soaked. Make sections, etc., with a razor blade and probe, or make a tentative arrangement of material Take a strip of glycerin jelly and pinch off a small portion, put on the slide with the material and heat. Be careful to apply the heat rather generally (all along the slide but donít burn your fingers) rather than in only one spot (which can crack the slide). Arrange material and gently add a cover slip.
It hardens in a minute and may be mailed when cool - which is almost immediately after labeling. Don't worry about the clearing aspect of Hoyer's solution, material usually doesn't have to be cleared to be studied or illustrated, or if you must clear it, first dip the most plant in lactic acid for a minute or so (or heat in the pure lactic acid) before preparing the glycerin jelly mount.
Note: Although you can put a dropper bottle of glycerin jelly on a hot plate to keep it liquid, the heat eventually turns the jelly brown, and the gelatin breaks down so that it will not harden.
Another note: Glycerin dissolves (eventually) calcium carbonate.
Also: The glycerin jelly mounts are like little sponges. Do not stack slides as the pressure will squeeze glycerin from the mounts and make a mess. This is true even if you do not add pure glycerin in the mounting stage.
See: Zander, R. H. 1997. On mounting delicate bryophytes in glycerol. Bryologist 100: 380Ė382.