Stage Two: Casing
"Casing" is a term used by mushroom growers to describe the addition of a top layer.
Although not all mushrooms need this layer, it is worth adding as it greatly increases yields.
Casing protects the grain from drying out and also provides a good habitat for baby mushrooms to form and develop.
We now use a new type of casing - dry polymer in a bag (which replaces the older "soil" in a tub). The dry polymer requires the addtion of hot water before use (see below).
Take your bag of dry polymer then simply boil the kettle and add 1/2 of a mug of very hot water to the bag (careful not to burn your fingers).
Close the bag and stand upright for about 30 minutes until it cools. Shake to mix the expanded contents.
Cut the top off the white grain bag (from Stage One) about half way up.
Pour the casing layer on to the top of the grain and shake gently to even out.
Fold over the top of the bag and add a couple of clothes pegs. Then cover the whole thing in foil - you should end up with something like this. Put it back in the airing cupboard at 25-30 C for 3-4 days. Go to
Stage Three