bowl finish

[Derek Voigt]

I have been working on my bowl turning a lot more lately and I have started to switch finishing from poly to more of a natural oil and wax finish. I was using just walnut oil and then trying the Doctor Wood shop walnut oil/wax combo. I have used it a hand full of times and thought everything was ok. Then I had a large walnut bowl that saw a little bit of rain. So I wiped it down and noticed several spots that looked really dry, especially in the endgrain areas. So I added another layer of Doctor woodshop, but noticed it still looked dry the next day, so I did another coat, and then a 4th coat, and it still seem to be dry.


What is going on here? Is this normal with oil finishes that don’t build layers on top of each other? Do I just keep applying oil every day until it doesn’t look dry anymore? Should I have sealed it with a coat of a film finish first?

Thanks,
Derek

[William Bachtel]

Water is a bowls worse enemy . General Finishes wood be my choice. About the water spots, when that happens to me, it takes two or three coats to get it back to normal. Wood and water don't mix.

[Pat Scott]

First off, congrats on not using poly anymore! Straight out of the can poly is not a good finish as it will create a film or top layer. Once that film is compromised the only way to repair it is to sand the entire bowl back to bare wood. IF you want to use poly straight from the can, thin it 50/50 with mineral spirits. Now what you have is a thinned poly that will penetrate into the pores but not build on the surface. In order for the thinned poly to create a film on the surface, you'd have to put on a bunch of coats. Obviously stop before that happens, as 2-3 coats is usually sufficient. By the way, if you add a little walnut oil or linseed oil to your thinned poly, you've just created your own Danish Oil.

You might have to wet sand the entire bowl to get the spots to go away. If you have a vacuum chuck this would be easy to remount the bowl and sand with Doctors oil. Dip a towel or rag in the oil and wet the entire bowl first, then dip your sandpaper in the oil and start sanding. The sandpaper will develop a slurry but will keep cutting. If you stopped sanding the bowl initially with 320 grit, then you might try dropping down to 220 or maybe even 180 and work your way back up.

If I remount a bowl with an oil finish on my vacuum chuck, I started to cover the foam on my chuck with Saran Wrap or stretch wrap. I tape 3" wide x 6" long strips of Saran Wrap over the foam and tape them in place. It only takes 3-4 strips. Saran Wrap keeps oil from being sucked into the foam on the chuck. You'll know if that happened because the next time you mount a dry finished bowl on your vacuum chuck, when you take your bowl off the chuck after finishing the bottom you'll see a dark ring in the bottom of the bowl! Don't try to sand the ring out, just wet a rag with mineral spirits and wipe the oil off. A plus is the Saran Wrap seems to give me a better seal and has increased my vacuum readings.

"Should I have sealed it with a coat of a film finish first?" NO

[Reed Gray]

The walnut oil can take a week or more to dry. Once dry, the spotting is minimal to not at all, which could be part of the problem.

robo hippy

[Leo Van Der Loo]

Walnut oil use as a good finish is overblown IMO, it is at best a semi-drying oil, with a iodine value of 120 to 135 it sits right at the edge between a non-drying and a drying oil, (drying meaning polymerization).

To get this oil to harden up you’d have to heat it and even then it takes weeks if not months to harden, you might as well put mineral oil on it :)

[Derek Voigt]

Walnut oil use as a good finish is overblown IMO, it is at best a semi-drying oil, with a iodine value of 120 to 135 it sits right at the edge between a non-drying and a drying oil, (drying meaning polymerization).

To get this oil to harden up you’d have to heat it and even then it takes weeks if not months to harden, you might as well put mineral oil on it :)

what finish do you recommend then?

[Leo Van Der Loo]

what finish do you recommend then?

Faster hardening oils are Boiled Linseed Oil and Tung Oil and even faster is Polymerized Tung Oil, where I personally use PTO, as it give a smoother finish than Tung Oil and hardens faster and harder.

BLO does work well, is not as fast as PTO and yellows more over time, wich I dislike on most light colored wood.

Here’s the low down on these two oils, if you are interested in the how and what of it.

http://www.sydneywoodturners.com.au/site/articles/finishing/oils.html

If you have lots of time Walnut oil will harden somewhat and yellows less than either above.

[Doug Ladendorf]

I just finished a couple of platters on which I used shellac, cut back with steel wool then Watco Danish Oil. By using the shellac first it reduces the continued absorption of oil. DO has BLO and some varnish to help create a hardened finish when fully cured.

[Brice Rogers]

Leo, thanks for the tip on the polymerized tung oil. Could you suggest some of the brands that you are familiar with? I see a lot of different tung oil products (Rockler, Minwax, Zar tung oil wipe-on, Formby's, etc. Although they all say tung oil, I'm not sure if they really are, and I'm not sure which ones are polymerized. Suggestions?

[Leo Van Der Loo]

iQUOTE=Brice Rogers;2576300]Leo, thanks for the tip on the polymerized tung oil. Could you suggest some of the brands that you are familiar with? I see a lot of different tung oil products (Rockler, Minwax, Zar tung oil wipe-on, Formby's, etc. Although they all say tung oil, I'm not sure if they really are, and I'm not sure which ones are polymerized. Suggestions?[/QUOTE]

Brice be aware that Tung Oil Finish like sold by Minwax is not Tung oil at all, there is not a drop of Tung Oil in it, it is supposed to make a finish that looks like made with Tung Oil

I use the POL from Lee Valley

[Brice Rogers]

Thank you Leo. I looked up Lee Valley and see that they have a polymerized pure tung oil finish and a polymerized tung oil sealer. So, I suspect that you are referring to the finish rather than the sealer.

Are there any issues of shelf life or setting up in the can?

[Leo Van Der Loo]

Thank you Leo. I looked up Lee Valley and see that they have a polymerized pure tung oil finish and a polymerized tung oil sealer. So, I suspect that you are referring to the finish rather than the sealer.

Are there any issues of shelf life or setting up in the can?

OH yes, the Polymerized Tung oil will react with Oxygen in the air, I have written about this here before some people use collapsable bags, I use a re-closable Grolz beer bottle and add water to the bottle to keep the bottle full. (oil floats on water and is an inexpensive way to keep the air away and preserve the PTO)

More water as you can see in this picture, and I have been doing this for several years already :)

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