Woodturner's Finish: a question about sanding

[Eric Gourieux]

I've gone through a few cans of WTF (my wife doesn't like that acronym) but have always applied off of the lathe. I usually apply 6-8 coats, sand, and then apply another4-5 coats. Today, I applied it on the lathe on a few 6-8" diameter pieces using a blow dryer to speed up the process and came across a bit of a new dilemma. After applying approx 8 coats I had a nice looking gloss finish. I sanded lightly with 600 grit and noticed ridges that run around the circumference of the pieces - not unexpected, I don't think, since I applied with the lathe running. Unfortunately, both pieces have moved enough that I can apply with the lathe at 100 RPM, but sanding has to be done by hand with the lathe off. Anyway, here are a few finishing questions:

When I sand after 6-8 coats, should I just sand to smooth out the largest ridges and drips or sand until the finish is completely smooth? Remember, I'll be applying another 4 or more coats after sanding.

Will subsequent coats of WTF adhere if sanded with 600 grit or does it need a lower grit sandpaper in order to "grip"?

What if I apply after buffing with Tripoli and WD and decide to add more coats? I'm going on the assumption that WTF doesn't burn into previous coats and needs the sanding to provide "grip".

Finished photos will follow

Thanks in advance for your input.

[Kyle Iwamoto]

In my OPINION, you're putting too many coats before sanding. I sand after every 2 coats. I try to take as much finish off as I can on the first sanding, after first 2 coats. I think getting to almost bare wood takes all the finish off, but leaves the finish in the grain "valleys" of the wood.

My wife thinks "WTF" is cute.

[Eric Gourieux]

Kyle,
I'll try sanding sooner to see if that helps. But, in this case, the "valleys" are actually made by the application of the finish. They run the entire circumference of the wood.

After 2 coats and then sanding, do you apply a few more coats and then do the final sanding? Or, do you apply a second time, sand, and then apply a third time?

[Bernie Weishapl]

Eric I have found that I apply 2 or3 coats. This is turning the lathe by hand and then sand to smooth. I apply 2 or 3 more coats and lightly sand just to smooth it. The last 3 coats or so are with the lathe running at around 150 rpm since that is my slowest. I generally put 9 or more coats on. I agree with Kyle that 8 coats is to many between sandings. Also be careful how much finish you put on your applicator. If it is dripping it is to much and when running the lathe you will get those deep valleys in the finish kinda like putting to much finish on and getting runs. I dip and then kinda squeeze out some from the pad I am using.

[Dave Mueller]

Guys,
What are you using to apply the WTF? It seems that the film thickness would be a function of the application method - spraying thickest, brush medium and pad (wipe on) thinnest. That would affect the probability of sanding through the finish, wouldn't it? Which do you prefer?

[Jamie Donaldson]

...so applying to a moving piece is not a process I would recommend. I build several initial coats, then sand to level before any more applications. Any more coats without sanding simply replicate any imperfections from the initial coats.

[Mike Cruz]

Eric, I sand after about every 3-4 coats maximum. Otherwise, the ridges start building up. Also, if you are getting ANY kind of drips, you are putting it on too thick. Each coat should be ultra thin.

[Kyle Iwamoto]

After 2 coats and then sanding, do you apply a few more coats and then do the final sanding? Or, do you apply a second time, sand, and then apply a third time?


After the first 2, and sanding with 320, I apply 2 coats, sand with 400, 2 coats then 400 again. If the finish looks good enough, I lightly sand with the 400 to get the nibs, then run through the lower grits of MicroMesh. If the surface is still "rough" I do 2 more coats and MM. I find it rare to have to put more than 8 coats. I getting to like WTF more and more. Wipe On Poly is stil my fav though. I'm currently trying shellac under the WTF. Same process. 2 coats of shellac.


I apply the WTF with a Costco blue paper towel. I don't do it on the lathe.

[Dave Mueller]

Thanks, guys...helps a lot.

[Eric Gourieux]

Thanks for the help. I see a theme developing. Fewer coats before sanding - and thin coats. I hope to post the finished projects soon.

[Rick Markham]

Dave, I found the opposite to be true, wiping on actually gives a much thicker coat than spraying. This stuff is a bit tricky, especially finishing on the lathe. It took me many many many times (enough to make me question whether it was worth the effort) to get a great sprayed finish with WTF. I know, a lot of folks don't have a problem with it, I did.

Eric, There is definitely a learning curve to this stuff, but it is worth the effort IMHO. I sand until the finish is smooth and even. Yes sanding to 600 will work, the new layer of finish will stick to it, (you can sand to 1500 if you want it will stick to that too. you certainly don't need too) The thing I have noticed most about it, is if you build the layers too thick too quick, you are going to end up making more work for yourself. I personally have found spraying the best method for me, I can wipe on a perfect gloss finish with WOP, but with WTF it always comes out uneven. So I spray!

[Dave Mueller]

Rick,
Now that you have figured it out, could you please help me. I have an inexpensive Paasch external mix spray gun, much like the ones used in the WTF videos. Is that the type you use? If so, what pressure and how much do you dilute the WTF. At 50/50 dilution with water and 35 psi, I get a lot of droplets and not an even coat. I assume that means more pressure is needed, but that is the highest pressure the small airbrush compressor puts out. Clearly I'm doing something wrong. The other thing I noticed at AAW and SWAT, where WTF had demos, spraying produced a very thick coat, almost like plastic - not what I am looking for. Any comments would be greatly appreciated.

[Glenn Barber]

Dave- Here is a link to an older thread about "Spraying WTF". Not sure if it has all your answers, but it is very informative! Lots of excellent tips and advice.
http://www.sawmillcreek.org/showthread.php?190692-Spraying-WTF&highlight=

Glenn