MITRA Forum Question Details

In high-quality artist's linen canvas, loom sizings are generally light enough that the fabric weave is easily receptive to studio sizing and priming with no need to launder prior to stretching. Some artists take the optional steps of pumicing, picking (removing slubs and irregular inclusions) and sponging canvas with water to render the surface uniform and to raise the nap.

There are acrylic-based, PVA, starch-based and oil/wax sizings. These are generally sold as branded, factory-formulated products, rather than as single-ingredient materials. Not all are applied to the finished fabric, but rather may be used just on the warp yarns, for example.

Laundering would remove residual starch but would also disrupt the uniformity of the weave pattern and result in a less flat surface, so in my opinion this is a "last resort" fix for a failed RSG sizing but not a standard or necessary step in preparing canvas.