The word canvas refers to a heavy duty weave of fabric. In Europe it’s first usage can be seen in the 15th century with the manufacturing of canvas made from linen or hemp for the clothing industry. (The less well off would have had their outer clothing made from canvas with the more affluent using canvas to line fur garments)
However, its origin can be seen to go back much further with the discovery in China of a heavy duty hemp fabric dating back to 8,000 BC.
Strong, waterproof and durable canvas has a wide range of applications and has been used to make everything from mail bags to sails.
Canvas for tents
Tents would have been traditionally made from leather. Early canvas tents used by the military would have been made from either linen or hemp canvas (the early bell tents – the sibley tent used by the military would not have been made from cotton canvas)
Duck is the name given to a tight weave of canvas. It is this weave that is traditionally used in tents.
Duck fabric is woven with 3 yarns, two yarns for the warp (the set of lengthwise yarns) and one yarn for the weft (the lengthwise yarn)
The weight of duck has been traditionally measured in oz weight per square yard although now it is commonly referred to in gsm per square metre.
The weight of duck should always be measured in its loomstate, this is the natural weight of the canvas before it has been treated with rot or waterproofing agent.
Typically canvas weights will increase by 20% once the canvas has been treated with all three agents.
Once a canvas has weathered a few times it will be naturally waterproof (the cotton weaves needs to get wet so it swells and fills in any tiny holes) For nearly all modern tents or tarps often a waterproofing agent is also applied in production. This waterproofing finish reduces the water absorption of the fabric, speeding up drying time and reducing the weight when wet. Waterproofing will however mean that your tent will take longer to weather as less water will be absorbed into the fabric with each soaking.
A good way to tell if you canvas has been/needs re proofing is to see if the water absorbs very quickly in the canvas and stops beading on the surface.