Tuesday, November 17, 2020

Thoughts on Water Based Polyurethane

 My experience with water based polyurethane is pretty limited. I do have a couple of projects that were finished with water based polyurethane but I have to admit I had my wife finish them. I needed them finished before guests showed up and I had travel plans and couldn't do it myself. That was also close to two decades ago.

Many of the YouTube wood workers I watch will finish their shop projects with water based polyurethane. I figured I may as well give it a try on my sharpening station. There was going to be a lot of water involved anyway so why not protect it from getting wet. Or at least protect the wood from getting wet.

So I bought a quart of General Finishes water based polyurethane. I picked General Finishes because it is what my local Woodcraft store carried and I use their oil based Oil and Urethane varnish on most of my other projects. 

So far I have applied three coats to the case, drawer fronts, and handles. I'd been planning on putting even more coats on the case except I got bored. It isn't like I am going to be soaking the project in water. It is just going to have water splashed on it occasionally. The third coat went onto the drawer fronts and handles tonight.

I know it is durable because my other furniture - including my table saw outfeed table - has held up for close to 20 years. While I think I prefer the amber hue given by oil based polyurethane the color imparted by the water based is fine. The odor is certainly less objectionable. 

The main thing I don't like about it is the application. Sure, the brush cleans up with water but with my wipe on oil I could just drape the rag I was using over a saw horse or the edge of the table until it dried. Another difference is my wipe on polyurethane is thin enough that it self levels. I need to worry about leaving puddles but it stays wet so long I can just make sure to wipe down the project one final time and I don't have to worry about it. Speaking of wetness the water based poly dries quickly which is nice for being able to put multiple coats on in a day but I also have to be careful to keep a wet edge. Also, my wipe on poly dries (cures) quickly enough since it is large part mineral spirits to put multiple coats on in a day.

My gripes are pretty much what you expect with a water based polyurethane so there are no surprises there. But despite my griping I'll keep using it for shop projects. The low odor and sufficient protection is sufficient to sell me on at least that use. Bob Flexner says you cannot thin a water based polyurethane but this can says you can thin it by 10% with distilled water. I might try that next time to see if it reduces brush marks.