In the slasher dyeing method, denim yarns in the form of a warpsheet are pre-treated with chemicals and followed by (multiple) dip dyeing in indigo. The sheet is then after-treated by washing, drying and sizing, and a last dry cycle completes the process.
It is a low-cast alternative to the rope dyeing method. One of the three main methods to dye indigo yarn, see also ‘Rope Dyeing’ and ‘Loop Dyeing’.
Source: Nouvelle de Nîmes Nº 5: The Denim Dictionary