Ask the Staff
I have a picnic table made of clear heart redwood. I also have 2 dogs that often climb on it while I'm at work. I just refinished it with spar urethane and I'm not really happy with the scratches that the dogs are leaving in it. What can I cover it with that will hold up to the weather and the dogs?
As far as clear finishes for outdoor furniture (not jumped upon by dogs), a spar varnish would be the product we would recommend. This is because a spar varnish is more flexible (softer) than a polyurethane top coat (polyurethane finishes are a type of varnish). The flexibility allows the finish film to better handle the wood movement that happens in an outdoor environment. This is why spar varnishes are used on boats. Also, due to the flexibility, if a dull impact happens, the varnish finish can give and may remain intact, whereas a harder finish like a polyurethane would be more prone to "crack" and let water behind the finish.
As far as being hard enough to resist dog toenails, people with wooden floors inside their homes have the same problem you are experiencing. Even durable, hard polyurethane finishes designed for floor use can be scratched by the toenails of a dog. The toenail of a dog is simply too hard and applies too much pressure in too small an area. A tile floor is a hard enough surface to keep dog toenail from damaging a floor, but I know of no finish for a wood floor that is hard enough not to be scratched by dog toenails. There could be some epoxies that would cure harder than a varnish. However, these are typically not very UV stable and so need to be coated with spar varnish with UV block to provide UV protection to the epoxy underneath. This does not gain you much as far as scratch protection, other than toenail scratches may not penetrate to the wood. The scratches will still be visible in the top coats of finish. People who really want to protect nice wood floors from dog toenail damage sometimes use this product:
Soft Claws for Dogs
You could also consider training the dogs not to jump up on the table (easier said than done) and then a standard spar varnish with a good 5-8 coats (and a refresher coat applied ever year), is the best way to protect your outdoor table with a clear finish.
with your woodworking questions. If yours is selected for publication,
we'll send you a free Highland Woodworking hat.