Darkening a Danish Oil Finish on Walnut

Thoughts on tweaking the color of Walnut after it has already been coated with an oil-based home brew.September 18, 2014

Question (WOODWEB Member) :
Yesterday I finished some solid walnut bartops for a client. Today I go onsite, and there is a note from the client that the tops need to be stained darker. They are finished with a single application of danish oil (1/3 BLO,1/3 poly, 1/3 thinner). This is the finish they chose and approved. I reinforced the continual maintenance that will be required, but they wanted the oil. Now they have the oil, and they want it darker. They are willing to pay for a refinish, but I have concerns about the process. If I sand the tops raw, will they even take an oil based stain after having been oiled? Is there some sort of glazing I could put on the existing finish and achieve a darker look? I build mostly furniture and rarely stain, never paint. The natural walnut tops look fantastic, I wish they would open their eyes and see it. In the meantime though I need to make a plan to darken them and I am at a loss. Any product or technique recommendations would be greatly appreciated.

Forum Responses
(Finishing Forum)
From contributor R:
I have tinted polymerized tung oil before with success, dump some dark (jacobean) minwax into oil, flood surface, and wipe as you normally would on a tung oil finish. Itís subtle so if you are being asked to dramatically darken, it probably won't get you there.

From Contributor J:
You didn't mention what kind of darker. If it is more brown you might want to accelerate the maintenance on the finish by evenly abrading the surface and mixing some asphaltum (gilsonite) into your maintenance mixture. Test it on an off-cut over your original finish mixture.

From contributor M:
I would not use an oil-based pigment stain, for starts. Although I haven't had your particular problem I would consider using a solvent based dye stain and try to penetrate the oiled surface having removed as much oil as possible. Acetone, L-thinner or Naptha would be a good place to start to clean the surface. I would think acetone would be the solvent for dye I would try first. I often spray dye stains as a first step in finishing after sanding.

The first thing I thought of when starting to read your submission was to put it in the sun or get a strong UV lamp and try to darken it that way. Sunlight always darkens walnut anyway and I would try that before using a chemical method. I don't know how controllable sunlight is but I darkened a walnut table top by leaving it outside the shop for a few days.

Regardless of what you use to remove the oil, you're not going to get it all. With that in mind, any stain may be blotchy. The nice thing about using a dilute dye is evening out the color needs to be done to a lot of woods and dyes makes it much easier. My concern with using a pigment stain in oil will be the tendency for it to bleed out over time and stain anything it touches.

From contributor R:
"Sunlight always darkens walnut anyway." That has been the opposite of my experience. I have found walnut exposed to direct sunlight over time to fade or blonde. I have not seen the bleeding in a polymerized finish. As with everything I am doing for the first time (as a lot of custom work is) do a test.

From contributor K:
Just recently we finished over a hundred 4'x10' sheets of walnut, and had them leaning against the wall in sequence to make sure everything was consistent. There were a few pieces that were overlapped to make room, and after sitting that way for a couple days (indoors) the parts that were not exposed to the UV were lighter. We had to tape/paper them all off (covering the darker part that was exposed to the UV) and set them outside in direct sunlight. I kept a close eye on them and after one hour and twenty minutes the lighter side had caught up to the darker side. The same thing happens with cherry.

From the original questioner:
Iím definitely not taking walnut into the sun. It will look like butternut in no time. Cherry oxidizes in the sunlight and darkens, walnut bleaches. I experienced it firsthand. I'm leaning toward the idea of an additive to the original mixture. I'll look into the material suggested. I don't think they want an extreme color change, more likely a subtle darkening. I almost think they want an antiqued look, so I thought some sort of glazing might work. I have never glazed anything, though, and don't know much about the products.

From contributor G:
Watco makes dark walnut and black walnut Danish oil. This would be an easy fix and easy for the customer to maintain.

From contributor O:
Contributor G has the correct answer and is quite simple to achieve. Create a slurry of the Watco oil with wet/dry sandpaper, allow to penetrate for ten minutes and then remove all excess oil with clean muslin or cotton cloth rags. Wet/dry sandpaper 500 or 600 grit. You may need two applications to achieve dark color.

From Contributor J:
Any true glaze will have to be locked down with a protective clear - probably resulting in a more formal finish than the thin oiled look you started with. The Watco idea is similar to what I mentioned. It is definitely worth trying on your sample piece. I think the original Watco darks used asphaltum as the colorant - acting almost like an oil soluble dye that mixes in a wide variety of wiping varnish diluents.

From Contributor B:
Oil is oil and there's nothing permanent about it. It's meant to be done and redone and (while we're at it) one thinned application of danish oil is not considered done. Read the can. If they want it darker, no problem. If they want it lighter, that's usually no problem either. A little soap and water and re-oil. If only all customer complaints could be solved so easily. The one that gets me is the slight blemish or natural wood discoloration below 15 coats of spar varnish.

From Paul Snyder, forum technical advisor::
Contributor J - are you saying soap and water will remove the danish oil?

From Contributor J:
The thing I worry about was the poly in the initial finish. The surface needs to uniformly prepped for a darker re-application to not have splotching.

From Contributor B:
Soap and water is the first choice. As has been suggested, you shouldn't have to remove any of the oil, just try an application of a darker shade. The slight polymerization of oil finishes does not create any kind of impenetrable barrier or seal.

From contributor I:
Contributor J has it right. He's not talking about canned danish oil, he's talking about linseed oil, "poly", and thinner. No one knows what "poly" means here since there wasnít a mention of brand or real product. Getting Watco to soak into something with a resin finish is going to be really difficult, just about as tough as removing a resin based finish by scrubbing with soap and water.

From the original questioner:
I tend to agree with Contributor J about the poly. That's my concern. I mixed my own finish - BLO, Minwax satin poly, and mineral spirits (1/3 each). A mix I've used successfully on many pieces of furniture. Obviously I typically use more than a single application (6-10 wet sanded in, followed by wax), but this finicky customer wants a raw look - as little finish as possible. I am going to try the dark watco oil on top of the finish tomorrow and see if it works. I considered a dark wax, but the client is afraid of sheen. They think a nice sheen means there is a film finish. It is a restaurant setting so the oil finish is going to deteriorate, quickly. They understand and sort of embrace that. I will absolutely not guarantee/warranty anything for them.

From contributor I:
Wow a restaurant setting? Don't they use a disinfecting spray on it for clean up a lot of times per day? Iím glad they understand it's all on them! I wonder about using a thinned flat black acrylic paint like a glaze? Get it on the wood, then buff off with a rag. It would fill the pores with black, it will cure hard and not change the sheen.