Waxed canvas is cotton that has been impregnated with a wax-and-oil blend. The wax sits in and around the fibres, which is why the fabric is water resistant, stiff at first and slightly scented. It is also why most normal cleaning advice is wrong for it.
What the wax actually does
The wax makes the surface hydrophobic, so light rain beads and rolls off rather than soaking in. It also stiffens the fabric, which is why a new bag stands up on its own and an old one folds more softly: the wax migrates and thins with use, especially along folds and where your hand goes.
That migration is not a fault. It is what gives a waxed bag its particular character — lighter along the creases, darker where the wax has pooled. A bag that never changes was probably not waxed, it was coated.
Cleaning without stripping it
Never machine wash waxed canvas. Hot water and detergent remove the wax, and the lining will shrink while the outer does not. Spot clean instead: cool water, a drop of mild soap, a soft cloth, and blot rather than scrub. Work on one small area at a time and let it air dry away from heat.
For mud, let it dry completely first and then brush it off with a stiff brush — you will remove most of it without any water at all. Grease marks can be blotted with a warm cloth, which lifts wax and grease together and leaves a slightly lighter patch you can even out with a re-wax.
Re-waxing
Once a year, or whenever water stops beading, the bag wants a fresh coat. Warm the fabric with a hairdryer on a low setting, rub a wax bar over the surface in thin passes, paying attention to seams and folds, then work it in with a cloth and let it dry overnight. It will look patchy for a day and then settle.
Do not overdo it. A thick coat stays tacky, transfers onto whatever it touches and attracts dust. Two thin passes beat one heavy one, and the bag does not need wax where it never gets wet.
What good ageing looks like
A well-kept waxed bag after five years is darker at the edges, lighter on the folds, slightly softer than new, and still completely water-resistant across the body. It will have earned a few marks. Ours have coffee on them and we are not sorry.