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Aging Cherry With Lye

 


Finishing Experiment: Using a Lye solution to darken Cherry lumber

I'm working on a project right now that I am building out of black cherry. I would typically use some sort of an oil finish on cherry (like Circa 1850 Tung-and-Teak, or maybe Tried and True) or if I wanted a film finish, then I would apply one or two coats of shellac followed by Varathane. This looks nice, and ages over time to a gorgeous dark natural cherry look.

However, several years ago I came across a document on a woodworking forum in which a woodworker used a solution of lye to accelerate the darkening of cherry. The results were gorgeous, and allowed him to produce brand new cherry baseboard that looked like it was already six-ten years old, and nicely matched the dark hardwood flooring that he had already installed. I quickly did some research and found a few other documents that also outlined similar experiences.

Basically, with time and exposure to UV light, Black Cherry will naturally age to a lovely reddish/brown colour. But you can jump-start that process by wiping down your lumber with a solution of lye. This can be quite useful if you are repairing an older cherry piece and need to fit in some new wood, or if you are trying to match another project, or if you simply would like to get a head start on the natural darkening process.

I finally got around to wanting to give this a try on one of my own projects. So here is a photo essay of trying this out on some sample boards.

 


 

Here are my three test boards. (Test #1) These are actual off-cuts from the cherry boards that I am using in this project. The right hand board will be the control board -- that one will not get any lye solution. The left hand board has the typical pinkish look of unfinished cherry The center board has a lot of sapwood showing on the left hand lamination, and the right hand lamination has a more darker greenish tinge to the cherry. This should give me a lot of different surfaces to compare.
All pieces (end grain also) were sanded to 150 grit with the Random Orbit Sander (ROS), then 220 grit with the ROS, and finally to 320 grit by hand sanding. The pieces were all then wiped down with a damp rag (shown here). Once dry, they were again lightly hand-sanded with 320 grit to knock down the raised grain.

I had read that the lye wash would raise the grain, but that you need to then be careful when sanding, as the colour is not very deep. I thought to try pre-raising the grain to avoid this if possible.

I am fortunate in that one of my wife's hobbies is soap-making. So she has lye crystals on hand, and is also experienced at handling this chemical. I used the proportions mentioned in the forum thread that I mentioned above, which was 1 tablespoon added to 1 pint of water.

Note, I googled up a few other references to people doing this, and they also used roughly those proportions. I actually used 1/2 Tbsp to 1/2 pint of water. Add the lye to the water (NOT THE REVERSE), and always add it slowly while stirring.

I kept stirring until it was well mixed. Note that I am using gloves. I am also wearing safety goggles. I am also doing this outside in my backyard (Though, I did not notice any scent at all). I am also using my wife's soap-making utensils which ONLY get used for this sort of stuff, not for food.
I wiped it on with a rag dipped in the lye solution. The first application was quite striking, as the cherry instantly turned a rich reddish brown.
Here is the first board complete. Even the sapwood looked far better than it normally would.
Both boards complete. They're gorgeous.
And compared to the control board, which gets no lye solution. After about 30 seconds, I washed them down with a vinegar solution (about 2/3 water to 1/3 white vinegar) to neutralize the lye.
OKAY SO FAR.... But here is where things diverge from what I had expected, based on what I'd read online. Pictured here are the boards after five hours. They've been drying indoors since this morning. The control board on the right has had one application of Zinsser Sealcoat (shellac) on the right side of the green tape. The two boards treated with lye are looking much much much uglier. The sapwood is now showing through more prominently. The rich red has faded. The board on the left is looking very blotchy and uneven. The right side of this board has a darker section, and the left side looks more pale.
Here is a close-up of the end grain/front-corner of the left-hand board, showing how it is looking uneven.

I was not happy. I was close to throwing in the towel. I'd thought that I'd followed all the guidelines, but I was not at all liking the results. Maybe I should just stick with the familiar?

 


So I went back to Google and searched more online... I found another reference to this which contained a hint... The vinegar wash might have been the culprit.

I tried one more test board. (Test #2) This time after the Lye wash I left the board to dry for over an hour. Only then did I come back and wash it with the vinegar solution. Here is an outdoor photo showing the new board inbetween two of the old boards. On the left is the blotchy board. On the right is the control. The new center board shows a much more even colouration.

Here is an indoor snapshot with the new board at the bottom/center.

It looks MUCH better.

I was happy enough with these results to proceed with testing the finish further. First, I applied some shellac (Zinsser Sealcoat) to a portion of the board.

Next, I applied two coats of Varathane. I usually use this product when I want a film product, such as for a bookcase. I've been using it for 15+ years, and have the technique down for getting good results.

Pictured here is the control piece above a piece from Test #2. Both had one coat of shellac on the right side. Both have had two coats of Varathane over the whole piece. Both have sat in the sun for a couple afternoons. Yet both show almost no difference now between the two sides. I'm now wishing I'd put on two coats of shellac on a board to see if that makes a difference.

 


So far, I was moderately pleased with Test #2, but not exactly overwhelmed. I was not planning to take this any further, but after a conversation with a woodworker I know who was experienced with this I got a few more pointers that I wanted to try out.

Here is what he explained to me:
In his experience, after the Lye solution dries on the board, the cherry looks "like dirt". (I agree it looks dull.) However, it lights up once you apply the finish. Also, depending on the finish I was using, I could even skip the vinegar wash. With an oil finish, like a Tung oil, he recommends the vinegar wash. With a lacquer or polyurethane finish, he suggested I could skip the vinegar wash.

Time for Test #3. Here are the two board after being washed with the Lye solution and left to dry indoors.

Same two boards from Test #3, after two applications of Varathane. Wow.

Disclaimer: I am getting better, but the colours in this photo are a bit off. It is a touch less red, and there is a bit less "depth" in the grain on the left of the lefthand board than in this photo. Still, lovely.

And here is a pretty accurate photo comparing the control board (top), Test #2 (Middle board) and Test #3 (bottom board). Test #3 is definitely a richer redder look than Test #2. The control board is quite pale in comparison.

I plan to keep giving these boards a "suntan" -- a few hours outside in the sun each day -- for several days, to see if that makes any difference in these results.

 

Thanks for reading!