If you unfold or unroll a canvas awning, tent or backpack only to meet up with a blast of musty odor, the time has come for a thorough cleaning and airing out of the item. Caused by prolonged storage in damp environments, musty smells coming from canvas typically indicate the growth of mold or mildew. Refresh dank canvas not only to remove the smell but also to sanitize and protect the item from future degradation or discoloration.
Brush away any loose debris on the canvas item with a stiff broom or brush. Knock off any stuck-on matter. Employ only a plastic or natural-bristle broom or brush, rather than wire or other abrasive materials, to prevent damaging the fibers.
Hang the item outside and gently rinse it with water using a garden hose with spray nozzle. Avoid high pressure, as it may wear out the fibers or embed dirt even further.
Fill a spray bottle with white vinegar and spray the entire canvas. Vinegar effectively kills mold and mildew.
Create a sudsy solution of dish soap and warm water in a bucket. Scrub the canvas with the soapy water with a scrub brush. Work in circular motions starting at the top of the item and working downward. Continuously rinse the canvas with fresh water during the scrubbing process. Washing the canvas with soap removes any remaining mold and mildew. When finished, give the canvas one more thorough rinse then leave it to dry.
Give the canvas another whiff once dry. If any musty smell remains, choose from two options for further sanitization: Employ a vapor-steam cleaner or scrub the canvas with a solution of one part baking soda, four parts white vinegar and four parts water, then rinse.
Allow the canvas to dry if additional cleaning was done, and then spray the canvas with a coat of canvas protectant. Canvas protectant shields canvas from water and ultraviolet (UV) damage.