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.

As I am told, Sunbrella is a synthetic and not canvas, thus the 303 is the recommended product. For treated canvas, Francesca is correct, Canvak, $ 35.00/gallon at Cabelas.

Actual cotton or linen canvas, or duck, we used to waterproof with wax (1950's). Lowest cost was self-mixed paraffin in a petroleum solvent that would evaporate, but that is probably illegal now in many places trying to control evaporative emissions. You could buy it pre-mixed at least through the 1980s, haven't seen it in camping stores since all consumer tents went to synthetic fabrics instead of canvas.

We used to brush it on, lost too much of it, and breathed too many toxic fumes, trying to spray it. A really good coating would about double the weight of our tents.

Modern approach, used on synthetics that aren't backed by a waterproof coating, is silicone, usually in a spray bottle. This coats the fibers (or soaks into leather etc) but doesn't necessarily fill the space in the weave, in the way that cotton is waxed. It might have an adverse effect on cotton, because that depends on fibers getting wet in order to close up the weave and repel water.

So what you use might depend on what fabric you actually have.

Once fabrics no longer maintain water repellency on their own, you can use 303's High Tech Fabric Guard, found here.

I just did this on my Fleetwood's Sunbrella, which is a woven fabric and is in fact specified for use by Fleetwood and Sunbrella for restoring and maintaining canvas and other materials water proof.

Unlike other products, this will not affect the breathability of the canvas and does not suffer many of the undesirable effects of silicone based waterproofers.

The trick I found when applying it and not having overspray is to gently pull the trigger on the spray bottle, slowly and steadily.

I had a good validation of its effectiveness when I was interrupted during application and had a rain the following day. I was half-way through a panel when I had to stop. The half without HTFG was wet, wicking moisture into it but not all the way through it, as you would expect canvas or similar material to perform. The section that had the 303 HTFG had water balling up on the outside with no signs of absorbing any moisture at all, shedding it at the slightest bump but it still is breathable. I was convinced and am now thinking about using it on my tent, my rain ponchos (fabric), etc.

The downside - it is expensive. I went through four 16 oz. bottles at $15 ea. from my local Ace Hardware. I bought out their stock and had them order another bottle so I could finish. But now I have every confidence that the material sections will not leak.

On the vinyl sections, I had previously used 303's Aerospace Protectant and those sections look brand new and have UV protection for a couple of months.

You might do what I do here. I actually started doing this from day one as we was needing some GIZMOs on both tent ends to help with heating and cooling periods.

The tarps are 9X12 and are held in place with stretch rope. Easy to put up and folds in rather nice as you can see.

We attach the 9X12 tarps into the rain gutter on both tents before we raise the roofs. Actually helps out alot when putting up the roof in the rain too..

Some folks think it may look abit like trailer trash trash but works for us. My 2008 Trailer tent material still looks like brand new...







We have put a 20x30 tarp over the whole trailer a few times and extended the front out over the awning which makes a large awning sitting area under the tarp. This is done alot camping in the Smokey Mtns camp sites where alot of folks do this. Its like a rain forest there after a rain storm - trees will drip water for days...

Roy Ken

Cotton canvas is naturally water repellant due to its weave. Once properly saturated it will absorb no more, close its pores, and water will slide right off. That's why it's been used for eons for everything from sails to tents to covered wagon covers.

Keeping enough pitch to allow natural drainage to happen is enough for real canvas, but if you want to totally waterproof it I recommend "Canvak" an oil-based preservative that's been around for years. Link. That stuff will waterproof cotton fabric well enough to use it for a bathtub.

Do bear in mind that sealing up the pores with compounds like the above will eliminate the breatheability that makes canvas so superior to synthetic fabrics.

Get a spray can of tent water repellant. Wall Mart in the camping section, any Sporting good store like Dicks, Cabellas, Gander Mountain. Spray outside, all over, let dry. Repeat a second time after a few days. We did this with our PUP at lest once a year, every year.