"When the mycelium is midway through the casing, the entire layer is thoroughly ruffled down to the bulk substrate. The agitated and broken mycelium rapidly reestablishes itself and within three to four days it completely colonizes the casing. The result is an early, even and prolific pinhead formation. Before using this technique, the grower must be certain that the substrate and casing are free of competitor molds and nematodes"

The Mushroom Cultivator
Chapter 8 The Casing Layer
subchapter 6 Casing Colonization
pages 136-137
paragraphs 4-5