What does it mean to patch a casing and what is it good for?
Patching a casing refers to the process in which the initial, aggressive "spots" of mycelia poking through the casing layer are covered again by adding a small thin mount of your original casing material to the spots. These initial colonization spots may be the first to appear usually within the first few days after casing. The point of patch casing is to allow the rest of the casing layer to "catch -up" with the initial spots.
Usually the casing will be permeated more evenly, in that case there is no need to patch-case.
An even casing layer will have less of a problem with aggressive spots than an uneven casing layer, but this is not always the case. Just keep in mind that the more evenly the mycelium appears in the valeys of the casing layer , the more chance of an even pin set. And an even pin set means more yield per sq. foot on the first flush than a non -even pin set.
Don't make the mistake to cover every hint of a mycelium with more casing material for a prolonged time, this leads to nothing.
Once the mycelium is more or less visible in the valeys of the casing layer throughout the casing surface, it's time to put it into the fruiting chamber.