Wood gunnel refinishing

I need to refinish my wood gunnels which I think are oak. It is weathered in some places(turned grey) and I don’t want to sand it if I can avoid it. (OK, I admit to being lazy if/when I can get away with it.) Years ago, at least 20, I was able to buy phosphoric acid from the marine store and paint it on my teak and let it sit for awhile then wash it off with a stainless scrub pad and it took off all the grey wood and old finish with very little effort. Great stuff! Now the marine dealer says they don’t sell it anymore and haven’t for years, he thought for liability reasons. The hardware store doesn’t sell it either and neither does home depot. So, does anyone have any ideas what type of business might carry this stuff locally, or what else it might be used for besides etching wood? Thanks,


Oxlaic acid

– Last Updated: Jan-03-04 11:17 AM EST –

You might try oxalic acid wood bleach, my local hardware store has it, so it should be available. I just treated an entire old wood canvas canoe (without the canvas on it) with it, and it really helped lighten up the wood, and did not seem to hurt anything.

Careful with acid treatments on oak.
You may find that some chemicals cause considerable chemical darkening. Check a patch before you dive in. Personally, I would sand the gunwales and then use Watco oil.

Good point
G2d makes a really good point about oak, FWIW, here is a little article on wood bleaches with a paragraph on oxalic acid.


Yeah, I used chemicals to darken alder
when building a kit harpsichord. Works beautifully, but it is essential to “rehearse” on samples. Oak is especially inclined to turn very dark.

Actually I wonder if those thwarts are oak. Any chance they are ash? Oak has never been a popular gunwale wood, and has been used only by builders not inclined to use the right thing. Even mahogany is a much better wood for gunwales than oak.

Thanks for the link mferwerda
it was real interesting reading. Although I wasn’t trying to bleach the wood as to actually dissolve a thin layer. The way the phosphoric acid worked was by dissolving a layer by turning it to mush. It still looked like nothing had happened, that is the wood was still grey after it got done working but as soon as you scrubbed it with a scrub pad it all wiped off easily, kinda like oven cleaner on baked on grease. Underneath all of the old was all the new unweathered wood in pristine original color. g2d as to whether the gunnels are oak or not I just went out and looked again and they very difinitely have that grain that oak has so yes they are oak unless there is some other type of wood that looks like oak that I don’t know about. And BTW the whole canoe is very heavy, likely because of the gunnels. The thwarts are probably ash but definately not oak. This canoe is the slipper that I am talking about in the hull deformation thread. It’s only supposed to be 46 lbs but I swear it weighs 50 just to hoist it. The gunnels may not be the original ones for the canoe but I don’t know for sure. The shaping on the outer edges and the way they are installed makes them look like it was done in a shop and so I had always assumed they were original since I recall reading somewhere that the Slipper has walnut decks which this does. And ultimately I may end up sanding the things, I know . But since I will be working on it anyway to test the shorter gunnels ideas with clamps I thought I’d use the momentum once started on the project to go ahead and do something about the gunnels. Although come to think of it If I could knock off 5 lbs. assuming the thwart idea worked I would love to replace the gunnels and thwarts with aluminum. That way I would kill two birds with one stone; get rid of some excess weight and save having to refinish the gunnels every year or so.


Interesting. Mad River customarily used
ash for gunwales, although they made a 13’ Compatriot for me in '73, with sitka spruce at my request. The spruce was stiffer, but easier to break and more inclined to rot. I’m not sure why oak would have been used. The suitability of split white oak for baskets suggests that white oak might make a reasonable gunwale wood.

be careful
with whatever chemicals you use on the gunnels to not get it on the hull. you didn’t mention what material your hull is, but many chemical stripper and bleaches will damage the surface finish of your hull. This is also true of Watco oils. If you are applying stripper or oils that could run down onto the hull I suggest you put the canoe upside down on a rack that you can work under. Drips will just drop to the ground.