SUBSTRATE PREPARATION
Some substrate will need a preliminary treatment. Straw generally needs to
be chopped. Paper will also need to be shredded. Maize cobs and stalks must
be broken up. The best equipment for this kind of work is a hammer mill
with a “screen.” “Screens” for hammer mills are heavy steel plates with holes
cut into them (Fig. 6). Small pieces of wood, tree branches, etc. can also be
handled by the hammer mill. There are several reasons to shred things. The
most important is to increase the surfaces where the mushroom mycelium
can grow, but another is to make the substrate a little more compact and
easier to handle.
The next two things that must be done are wetting and pasteurization.
The two basic methods of wetting and pasteurization are describe in Chapter
2. The most efficient for space, time and heat, we can call the hot water
method. In the hot water method, water is heated in a large container to 55-
60°C (131-140°F). NOT MORE THAN 60°C (140°F) (Fig. 17)! Then dry
substrate materials is added to the water. Ideally the water should just cover
the substrate. Let that stand for 30 to 60 minutes. NOT MORE THAN 60
MINUTES! At that time drain the substrate and place it where it will cool
slowly. It should be 25°C (77°F) 16 to 20 hours later. At the end of those 16
to 20 hours, and at 22-25°C (71-77°F) the substrate will be spawned.
The hot water method can be used for substrate that has gotten wet, but
more care is required and some of the advantages are lost. If any of the
substrate is wet, the water should be closer to 60°C (140°F) than to 55°C
(131°F) the temperature must be monitored closely as the substrate is added
and never allowed to be less than 55° (131°F). When dry material is used,
everything that is wetted with the 55-60° water is pasteurized. If it is already
wet, we can not be completely sure it has been adequately heated. For that
reason wet material should be held for nearly the full 60 minutes