how do you waterproof canvas?

Thanks for all the responses. Our canvas is cotton. There is no hard top to the camper, so lots of canvas to cover. It is a true fold out "tent on a box" (4.5 x 6 feet when closed) with a hard door that is zippered in place. It has two double beds and a twin dinnette set up. That's it. It was built with no inside lights, toliet, AC, heater, etc. We put in a 4 plug recepticle, small ac window unit near the floor and portapoti. It has been everywhere including Alaska by many family members over 50 years and was not new when mom and dad bought it. Still has a lot of life in it and memories for new generations.

Thanks again.