Can you waterproof a canvas tarp?
Apply Adhesive Spray
Adhesive spray acts like a primer, so we need to apply it in a nice even coat so that the water resistant coating has something to stick to. Stand about six to eight inches away from the tarp, and move as you spray it.
Most tarps on the market today are either waterproof or water resistant. But some tarps simply aren't designed for exposure to water. And as you can surely guess, some tarps hold up against the elements a lot better than others.
Polyethylene has been proven to be the only thoroughly waterproof material for tarp construction, so this tarp can ensure that the underlying products are not damaged. It's a multipurpose product and has many different uses and applications.
Since canvas tarps are breathable, it covers material that needs to allow moisture to escape. Canvas tarps also cover construction machinery and equipment, protect surfaces and tools, or wrap hot pipes in a refinery. Canvas tarps are treated with chemicals to make them mildew, water, and, when required, fire-resistant.
Natural cotton fibers allow canvas to be a breathable yet water-resistant material. This allows canvas tents to maintain comfortable conditions and protect you from the elements, but heavy exposure to water can eventually make its way through the fabric's weave.
Canvas fabric is known for being durable, sturdy, and heavy duty. By blending cotton with synthetic fibers, canvas can become water resistant or even waterproof, making it a great outdoor fabric.
For general use, such as covering items, look for a lightweight blue tarp that has a thickness of at least 5 mils. If you're using the tarp for transporting goods or covering machines and equipment, you should look for a heavy-duty tarp with at least 23 mils of thickness.
Wrap the tarps from the bottom up.. this creates an overlap so water should not get inside… if your project requires more tarps use one as a “cap" to go over the top. It will help direct water down. Same as any other impermeable object - either keep it dry, or shape it so that the water runs off rather than collects.
It doesn't take long before the fabric rips and deteriorates, but a waterproof tarp doesn't allow water to soak through and reach the roots of trees, bushes, and flowers. With a tarp that allows rain to pass, water gets through, but the material lasts longer.
Water resistant tarps can withstand the entry of water into the fabric for a short period of time while waterproof tarps offer complete protection from water or moisture. Waterproof products can be taken under water (submerged) and will maintain impermeability, but resistant products cannot.
How long will a tarp stay waterproof?
Tarps are made of polymeric materials that are resistant to water, ice, and air. Tarps typically last up to 90 days on the roof, while those constructed of more robust materials can last up to two years.
The Polyethylene Blue Tarps are 100 percent waterproof, generate shade protection and are tear, abrasion, UV ray, acid, rot, and mildew resistant.

One of the easiest ways to waterproof your canvas bags is to use waterproofing sprays and seam sealers. You can usually find them at outdoor and camping supply stores. If you will use your canvas bag a lot in an outdoor environment, you may want to sun-proof it as well by buying a spray also containing UV protection.
You can use a spray bottle on small tops and covers. But music artists prayer for bigger boat tops
Denim or Canvas Apparel
To waterproof natural fabric like cotton, denim, or canvas, give it a thorough rubdown with a bar of Otter Wax. The wax won't leave any residue, but will stiffen and darken the fabric to give it a rugged appearance: We recommend denim shirts, work jackets, and old canvas weekenders.
You want 100%. Clear silicone caulking and you're going to add it to your mineral spirits at this