Problems with Danish Oil

Ken Martin

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For several years I have been finishing most of my turned pieces with a penetrating oil and then Minwax Clear Satin polyurethane quick drying spray finish. Almost exclusively I use neutral Danish oil in that process.
Lately, something has changed in my process. The new can of Watco Neutral Danish oil is not acting right. The first few pieces, it was fine, but the last few have turned very dark and it takes a week for the first coat of poly to dry.
I found a very colorful piece of coffinwood that I got from Byron and turned a bowl. It looked like a cross between a vibrant rainbow poplar and a really nice piece of canarywood. While the vibrant colors of red, purple, green, and amber on a milky background had faded to mostly variations of brown, it was still a strikingly vibrant piece when I had finished sanding.
Then I put the Danish oil in it. Within two minutes, it had turned a monotone dark, walnut brown and still isn’t completely dry (tacky) after 2 full weeks inside my central air conditioned house. The same thing happened to a walnut bowl, turning it almost black.
The oil looks fine, feels fine, and smells fine on my applicator (a piece of cotton T-shirt remnant) and goes on as usual. Then, within 5 minutes, the piece turns very dark.
What could be causing this? Heat?
 

JerseyHighlander

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It sounds like your new can of Watco may have a lot more solvent than oil. If you hadn't put poly on it already I'd say put it out in the sun or use a heat gun to flash off the excess solvent. With poly on it, I'm not sure how it would react.
 

Ken Martin

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Just for visual aide, I dug out the pics @Byron Barker showed us in his sales post and then a pic of the same piece of wood after I butchered it and put the Danish oil on it.

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trc65

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I have no idea what's causing the darkness unless it's just the natural darkening that oil produces when applied to that specific wood.

One test that I always use with drying oil/danish oil is to make sure that my applicator cloth has turned hard before applying any more finish.

My only thought with the poly not curing/drying is that for some reason the Danish oil hadn't fully dried and you trapped some solvent underneath the fast drying poly. Could be old (not fresh) Danish oil or maybe the wood absorbed more Danish oil than your normal pieces/practice.

I know nothing about coffinwood, but there are some woods that contain oils that prevent oils/resins from properly drying and curing.

At this point in time, you can keep the bowl somewhere with a lot of airflow. Apart from solvent evaporation, oils and resins (poly) cure from oxidation so adding airflow can sometimes help speed curing.

You can also try to remove as much of the sticky finish as possible using mineral spirits or naphtha and lots of rags. It will probably then need a sanding before anymore finishing. Once dry, I'd probably put a barrier coat of shellac before any top coat.
 

Ken Martin

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Thanks @trc65 , good idea about the shellac barrier. I’ll probably do just that.

I had a bowl do the same thing last year in drying as this one is doing. Patience prevailed when 16 days later I tried a secon coat of poly and it dried in a couple of hours.

It’s the darkening that I can’t figure out. Like I said earlier, it was a new can, recently restocked, and two previous pieces turned out great! Then this one looks like it got dunked in brown shoe polish!

after reading a bit of the links @Byron Barker sent me, I learned that the coffin tree is a conifer. Now I’m wondering if it has something to do with Ph and/or rosin. It’s just an interesting mystery that I’d like to solve before i work any more of it, if I ever get the chance.
 

Byron Barker

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Thanks @trc65 , good idea about the shellac barrier. I’ll probably do just that.

I had a bowl do the same thing last year in drying as this one is doing. Patience prevailed when 16 days later I tried a secon coat of poly and it dried in a couple of hours.

It’s the darkening that I can’t figure out. Like I said earlier, it was a new can, recently restocked, and two previous pieces turned out great! Then this one looks like it got dunked in brown shoe polish!

after reading a bit of the links @Byron Barker sent me, I learned that the coffin tree is a conifer. Now I’m wondering if it has something to do with Ph and/or rosin. It’s just an interesting mystery that I’d like to solve before i work any more of it, if I ever get the chance.
The bowl still looks really nice! I’m not experienced with finishes, but the experience I’ve had sealing cinnamon cutting boards (highly porous wood) is that the oil darkens wood if it enters deeply much in the same way water does when you wet a surface. I had used a hot olive oil/ beeswax finish on the boards and they went from pink to auburn and stayed that way.
 

trc65

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Something to try instead of the oil or Danish oil before poly is some plain shellac. It will "pop" the grain (maybe a little less than oil), give you a good seal, and is a nice base for the poly. Lacquer (nitrocellulose, not acrylic) by itself can do much the same.

Just make sure if you are using shellac before poly that it is dewaxed. Poly has problems adhering to anything with a wax component.
 

Karl_TN

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Just for visual aide, I dug out the pics @Byron Barker showed us in his sales post and then a pic of the same piece of wood after I butchered it and put the Danish oil on it.
It’s been my experience that eastern red cedar can turn also dark using just about any oil. In time it may have darkened like this anyway. Agree with Tim on using dewaxed blonde shellac as a sealing coat before adding a non oil finish For protection.
 

JonathanH

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The bowl looks great! Darker than preferred or not.

I've had a few projects that Natural Danish Oil turned too dark. I've become more picky about what I use it on.

To compensate I often do as others have suggested with good results- use a base layer of delayed shellac to seal & pop the color.
 

Ken Martin

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Well, as an update, the bowl finally got dry enough to put on a third coat. Let’s see how long this one takes to dry. The clock starts …now
 

Ken Martin

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FINALLY!!! :yipee:
After FIVE full months (that seemed more like five full years), I finally have a finish I can live with! It took six coats, and the last couple did dry in a couple of days each, but j

ust when I thought I had put the last coat on, it would dry uneven or run or something. But I finally got to put this one on the shelf today! :cool:

@Byron Barker , thank you for a beautiful piece of wood, but in the future, no matter hou much I beg, please don’t EVER sell me another piece of coffinwood!:lol2:

Happy Thanksgiving, Y’all!!!!

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Ken Martin

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Yeah, @Mike1950 a little research on my part would have gone a long way I didn’t realize that coffinwood was a resinous conifer. That explains a lot about how it reacted to the Danish Oil.
The real surprise was how long it took a coat -especially the first couple of coats- to dry! WEEKS for water based polyurethane to seal the wood and allow the next coat to dry. And just when I thought I was putting on the last coat, an area of resin would bleed through! It was an exercise in patience and humility. I was definitely NOT in control of any of this situation!!
 
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