Can this be used on a car's convertible canvas top

The best way to answer this question is to address what kind of material the convertible canvas is made from. Since our waxes are made from natural ingredients, they bond best with natural fibers that have lots of fibers to hold the wax seal. If you looked at something like polyester under a microscope, you'd see thousands of smooth plastic strands woven together to create the fabric. Our wax tends to get "pushed out" from these fabrics over time since it isn't able to bond with plastic (As opposed to something like a silicone spray that coats the microscopic strands with a thin layer of polymer chemicals). In contrast, if you looked at a natural cotton canvas under a microscope, you would see woven strands that are really fibrous and absorbent. The latter example is the best for waxing since it will "grip" the wax and hold it in place to provide a waterproof seal. It should also be noted, that our wax will work well with cotton/poly blends so long as the natural fiber is in the majority (ex: 60% Cotton / 40% Polyester). In short, if your convertible canvas top is made from a natural fiber such as cotton, hemp, or a poly blend, our wax will work great. If it's made from polyester or nylon, we would recommend getting in touch with the manufacturer directly to find out what product they recommend for waterproofing.

Would the solid or liquid version be better for waxing a Barbour coat?

Our Wax Bars and Fabric Dressing are fairly similar however the Fabric Dressing has a higher proportion of oils to wax. The higher oil content helps the wax to melt down faster, and is also what makes it ideal for re-proofing factory waxed or oiled garments in the traditional manner. Because our Fabric Dressing is melted down when applied, it permeates the fabric and yields a more factory-waxed and matte appearance. This is ideal for multi-layered coats and jackets, or for re-proofing factory-oiled fabrics. Our Wax Bars are excellent for one-sided waxing because it creates a seal on the top layer of the fabric. It’s ideal for hats, shoes, bags, and jackets where you wouldn’t want waxed fabric in direct contact with your skin. Our bars are also great for quickly re-proofing factory waxed and oiled garments. Our Wax Bars are really easy to apply, and just need to be rubbed directly onto the fabric. The appearance of this method will yield a really great look that will usually darken the fabric and give it a leathery, coated appearance.

What is the difference with otter wax and Paraffin Wax?

Otter Wax Fabric Wax is made from the highest quality beeswax and proprietary blend of of plant-based waxes and oils. And doesn't utilize paraffin, silicone, or other petroleum-based synthetic ingredients.

I want to wax a pair of jeans. What size should I get? Also after applying wax, would it ever come off when washing the jeans after normal use?

1 bar put a single layer on 3/4 of a pair of jeans. I am melting it in with a heat gun. My size is 30/30. Don’t wash them but you can spot clean them.