e.hutton caterpillar at
Mon Mar 3 05:07:55 EST 2003

Chris© wrote:

> Couple of questions about desiccant and preserving mushrooms.
> 1. Does desiccant loose it's efficiency? For example that packet that
> came with my coat. Will it still work after 12 months?
> 2. Where would you typically buy desiccant?
> 3. Is there anymore information on the Honey preserving method? How
> common is it used? How does that work?
> Thanks. I appreciate any help. As you know I have a growkit which is
> behaving it's self and working well for me. The next natural stage is
> to know what to do with these mushrooms.
I recieved the folloing by e-mail. As it has not turned up on the newsgroup
even now I submit a copy for information.

From: Tryggvi Emilsson <emilsson at>


These current discussions on the use of dessicants to dry mushrooms
reminded me of a little blurb that I rote for the "Spore Print" (L.A.
Mycological Society) in December, 1995.:

  "Illinois summers are often quite humid. My early attempts to dry
mushrooms involved spreading the precious specimens on a clean concrete
driveway. Sometimes they turned into maggot hatcheries; sometimes they
dried. However, when they did dry, they usually got scattered onto the
lawn by the wind.
  For a mushroom (or anything else) to dry, three things obviously have to
   a)water has to diffuse from the bulk to the surface,
   b)water has to evaporate from the surface,and
   c)moisture has to be carried away from surface to the surrounding air.

The rate of a) increases slightly with temperature (roughly T**(1/2) ).
The rate of b) increases steeply with temperature, but unfortunately, so
does the rate of spoilage. The rate of c) depends slightly on temperature,
but VERY steeply on air speed. This led me to speculate that the easiest
way to speed up drying would be to increase air flow.(Which is hardly
original- clotheslines have been in use for a LOOOONG time...  :-) ). To
test this conjecture I rigged up the following:

Equipment needed:

- One floor fan (the square jobs, about 2x2 ft.; available in K-Mart for
- Four bricks, empty coffee cans, or any other stands, about 8 inches
- One fly screen, off a window; at least as big as the fan.

Place the four bricks on the ground in a square, 2ft on a side. Lay the
fan, flat, on top of the bricks. Make sure that when the fan is on, the
airflow goes DOWN. Now lay the screen on top of the fan.
Split the mushrooms down the stem, then spread them evenly across the
screen. (If the air flow is upwards, things look fine initially, but when 
'shrooms dry they get blown all over the place!). Usually, if this is set
up in the morning, the mushrooms will be dry by late afternoon. It can run
unattended indefinitely.
Needless to say this scheme will not work if the ambient moisture is 100%.
That, however is seldom encountered, and even at 85%, it works
reasonably. It works quite well indoors, in air conditioned premises,
providing no one objects to the mushroom fragrance (and possibly
spores). It also works well indoors on drizzly, foggy fall days, when
nothing could possibly dry outdoors.
  Many improvements can undoubtedly made on this scheme. Eg, a coarser
screen, like 1/4 inch mesh hardware cloth, would probably increase the air
flow appreciably. Cardboard sides, on top of the screen, would permit a
larger load of mushrooms.
  Better drying rigs can be built, but most casual fungophiles may not
want to invest the time and money, OR, have to come up with a place to
store the contraption during the off season."

Additional comments, Feb. 2003:

I have used the method described above many times, to dry 20 lbs. of
Grifola frondosa at a time. In one or two days, in dry weather, they loose
85% of the weight, leaving about 3 lbs of pretty dry stuff. Additional
drying in hard vacuum, with a liquid nitrogen cooled trap may remove
another 1/2 lb of water. This step was taken just to answer the question
of how much water is left after the first step, but is obviously not
practical for most people. The removal of the last traces of moisture can
be accomplished just as well by drying in an oven, at 110 deg F, or with a
Conclusion #1: to dry 10 lbs. of mushrooms one must remove neary 9
lbs of water.
Conclusion #2: Abundant airflow is usually the key to easy removal of most
of the water from mushrooms. Slicing them thin is less important because
water diffuses very readily through the fibrous fungal tissue and moves
easily from the bulk to the surface where it evaporates.

On dessicants:

The little dessicant packets in consumer products (electronics, pill
bottles, etc.) usually contain silica gel. When dry, silica gel can absorb
about 20% of its own weight worth of water. (ie. moisture). In other
words, to dry 10 lbs. of mushrooms one would need nearly 50 lbs of dry
silica gel, which is hardly practical. Furthermore; suppose one put 100
lbs. of silica gel and 20 lbs. of mushrooms into a sealed barrel. Without
forced air circulation the rate of diffusion of the moisture from the
mushrooms to the silica gel would be too slow; the mushrooms would
probably spoil before they dried. Silica gel is good for keeping DRIED
mushrooms dry (in a sealed container), but not for drying fresh ones.

Anhydrous calcium chloride is sometimes used as a dessicant. However, if
given enough moisture, it will liquify into a thick bitter brine.
(Non-toxic, but corrosive to many metals)
Edwin Hutton
...Grant we beseech Thee that, ... during our journeys through the
Internet we will ... treat with charity and patience all those souls
whom we encounter. Amen.From <>

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