Waxed canvas is cotton impregnated with a wax blend. Water beads and rolls off rather
than soaking through, and the fabric creases into pale lines along the folds — the
look people buy it for.
It is water resistant, not waterproof
An afternoon of rain is fine. A day submerged is not. The seams are stitched, not sealed,
and stitching lets water through eventually.
Re-waxing
When water stops beading and starts darkening the fabric, it is time. Warm the bag with a
hairdryer, work a wax bar into the fabric in small circles, pay attention to seams and
corners, then warm it again to melt the wax in evenly. Leave it overnight.
Expect it to darken. That is the wax, and it is permanent, so do the whole bag rather
than patching one panel.
What not to do
Do not machine wash it, do not dry clean it, and do not put it anywhere hot enough to
melt wax you did not intend to move — a car in summer counts.