Question for experienced woodturner finishers.

[Glenn Lefley]

Firstly, sometimes when I get punky wood I put it in my vacuum with cactus juice. Essentially plasticizing the wood, making it impervious to water, and I'm guessing finishes. Can you still use tung oil etc on these type of pieces? Ie Danish oil finish.?

Secondly, when at a class we used an oil which put an amazing finish on the wood. Also available in colors. The osmo finishes. When reading about it it says not to sand higher then 220.
I would want to sand my stuff to 400. Does this mean this oil will not soak in properly, or should you put it on when sanded to 220, then sand more to get scratches out. Don't want to look into an expensive food safe finish if it isn't soaking in when sand to 400 and is only on surface and will wear off fast.

 

[hockenbery]

If you sand with the grain you can’t see scratches in domestic hardwoods with a 220 surface.
I sand most of my hollow forms to 320 figuring a plus 1 grit is safer.
I sand the first Waterlox finish coat with 400 and subsequent coats with 0000 scotch brite.
You can see scratches in the surface film finishes.

I sand hollow forms and Natural Edge bowls off the lathe so it is easy to sand with the grain.

When I sand spheres on the lathe to maintain and improve roundness. i’m carful to sand with the face grain to the centers last so that i’m Sanding with the grain lines. Generally I sand these with 400 because so much sanding happens across the grain.

Many Exotics will show scratches at higher grits.
Ebony will show Scratches at 1200.

Finials I sand with 320 and 400

 

[john lucas]

I find that finish can affect how far you need to sand. I did a flat wood test where I sanded up to 1200 grit in patches. I would sand the whole board with 150 grit. Then skip the first 2 inches and sand the board with 180. then skip the first 4 inches and start sanding with 220. Did this up to 1200. I used 4 various woods and had 4 samples of each. Then I finished them with various finishes, oil only, oil poly mix, lacquer, lacquer and oil. when all were dry I buffed them with the Bealle system. Then I took them to the club. Only one sample could anyone tell the difference beyond 400 grit. I did not do this test on exotic woods and they weren't turned. Sanding scratches show up worse on turnings and especially exotics. I try to sand with the grain whenever I can but things like finials or wine stoppers where you might have beads are impossible to sand with the grain so for those I have to sand finer than 400.
when you put a finish over epoxy or woods that have had a penetrating plastic it any finish will only stay on the surface. If it is a hardening oil it will dry but will still be on the surface. If you have any doubts about whether a finish hardens just put some on a piece of glass and let it dry.

 

[Odie]

I did a flat wood test where I sanded up to 1200 grit in patches.

That would make a great write-up, John.....

Note: I don't have much problem with domestic hardwoods sanding to 600 grit. Walnut would be the exception to that. Sometimes the very fine scratches left by the 600 grit only shows up after the Danish Oil has been applied and dried. This can be dealt with by using 0000 steel wool in a hand done version of random orbital sanding.

-----odie-----

 

[john lucas]

Yea Odie. I need to do the same test with turnings. Have thought about doing a whole bunch of wine stoppers with the same shape but different woods and different finishes. Each sanded to a different degree. the reason I did this test to begin with was I wanted to find out if I really needed to sand to the same high grit with each piece. I also wanted to see if film finished required more or less sanding than oil finishes. Not a definitive test at all but did show me that I didn't need to sand higher than 400 grit for most of my woods. There simply wasn't an improvement in the final product. So between cutting cleaner so I don't start with as course a paper, and not needing to sand to as high a grit on most woods, I've saved a lot of paper and time.

 

[Glenn Lefley]

I find that finish can affect how far you need to sand. I did a flat wood test where I sanded up to 1200 grit in patches. I would sand the whole board with 150 grit. Then skip the first 2 inches and sand the board with 180. then skip the first 4 inches and start sanding with 220. Did this up to 1200. I used 4 various woods and had 4 samples of each. Then I finished them with various finishes, oil only, oil poly mix, lacquer, lacquer and oil. when all were dry I buffed them with the Bealle system. Then I took them to the club. Only one sample could anyone tell the difference beyond 400 grit. I did not do this test on exotic woods and they weren't turned. Sanding scratches show up worse on turnings and especially exotics. I try to sand with the grain whenever I can but things like finials or wine stoppers where you might have beads are impossible to sand with the grain so for those I have to sand finer than 400.
when you put a finish over epoxy or woods that have had a penetrating plastic it any finish will only stay on the surface. If it is a hardening oil it will dry but will still be on the surface. If you have any doubts about whether a finish hardens just put some on a piece of glass and let it dry.

So what was the sample they could tell the difference on beyond 400 grit?

 

[john lucas]

I can't remember. It was too long ago. I do remember they could only tell on the next step at 600. Every step beyond that looked exactly the same.

 

[Gerald Lawrence]

I have not tried Watco on a stabilized wood but I have gotten it on metal while finishing . When this happens it will stay sticky since it works by penetration. I have started using Abralon from 500 to 4000 and love the result in removing scratches. So far have only used lacquer so not sure what penetration oil will get. Have not used osmo but it may be like poly in that when applying a coat after 24 hours dry time you should scratch (sand) the surface to get adhesion of the next coat. So from that I will surmise that the osmo needs a scratch pattern to adhere and does not penetrate.