Chemically Weathering Pine

Advice on how to give pine that instant touch of gray. August 16, 2009

I am trying to weather some pine for a Wainscot installation and I was hoping someone could help me. I was thinking of using muriatic acid to weather it but Iím not sure how to proceed after that? Can I just wait for it to dry and then use a water-based poly? This is going to be for a restaurant.

Forum Responses
(Finishing Forum)
From Paul Snyder, forum technical advisor:
Are you looking for the grey, weathered look? Will you be applying a protective clear finish over it?

From the original questioner:
I am looking for a grey weathered look. The paneling is #2 pine - lots of knots. Itís for a seafood restaurant so it does need something low maintenance and easy to clean. I was thinking of spraying water-based poly but Iím not sure how it will react with the acid.

From contributor W:
We just did some cypress like that with a gray wiping stain and a dark brown glaze. My guys used a wire wheel to gouge out the summer wood and raise the grain.

From the original questioner:
I already tried to vinegar/steel wool solution and it didnít give it too much of a grey. It just slightly tinted it. I know pine doesnít have a lot of tannin, so I did a few samples by misting it with tea. That gave me a brown finish. The color I get with the muriatic acid is exactly what Iím looking for. Iím just not sure if the water-based poly will stick to it long term.

From contributor R:
Other stains that work real well for your purpose are water-based dye stains. Lockwood makes a bunch of colors and they are easy to work with. Thinned down Latex paints are also another medium to contemplate. The same goes for a thinned down oil based paint. Iíve seen some deck paints/fence paints that look quite nice.

From contributor C:
If you like this look and are going ahead with it then neutralize the muriatic/hydrochloric acid before applying water coating! Otherwise you will just react the acid and that will affect the coating. Wash the pine with clear water a couple times (distilled) then make up a batch of boric acid and D water 4 oz to the gallon. Apply, let dry, and again wash the surface with D water let dry sand lightly with 320 or finer grit, then apply your coating.

From contributor G:
Contributor C - did you suggest neutralizing muriatic/HCl with boric acid? How do you neutralize acid with acid? Why not baking soda?

From contributor C:
"Neutralize" was the wrong word. Calcium carbonate (baking soda) would be fine to neutralize. Boric acid helps lift the chlorine from the surface so that the distilled water can wash it away much better and more thoroughly.

Personally, I don't use hydrochloric acid in strengths exceeding 5%. Itís way too harmful to the wood structure (lignin/cellulose) and I never leave it on for more than a minute or so. Yes I'm aware that many people do and in strengths above five.