Tung Oil, almost, but not quite:

Scratches after Tung Oil

Dennis J. Gooding

>Sounds familiar. Most likely at some point in your sanding you failed to remove all of the scratches caused by the previous paper. Typically, these do not become obvious until you have gone to very fine grits or have applied a finish coating. Often, it occurs when you try to use a worn-out sheet of paper along the way. It simply does not cut and merely burnishes the high spots. The only answer to to go back to a grit equal to or just finer than the one that produced the visible scratches and repeat the sequence. Having been bitten many times myself, I never attempt to sand an important (to me) work with anything but new sheets or disks of paper. Good luck. Dennis

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Re: Scratches after Tung Oil

Dinyar Chavda

>Dennis:

You bring up a point that has me confusled (isn't "confusled" a much more descriptive word that "confused"?---I really like it!). Anyway, I, too, have encountered David's problem, and probably for the same reason as you stated, i.e., worn out paper.

My question is, "How do you know that the paper is worn out?" I mean, one extreme would be to take one pass with it, throw it away, and use another piece (of the same grit), take another pass with it, throw it away, and continue. Obviously wasteful.

The other is to use it until such point as you could almost use 80 grit instead of kraft paper for burnishing! Obviously, there is a point at which one should move on to another piece of the same grit, but how do you know when that is? Seems like a stupid question, and probabaly is, but, nonetheless, has caused me the same (extremely frustrating and annoying) problem as David.

Any advice? Please be as specific and detailed as possible--don't worry about offending me by statingwhat you might think is obvous, because it isn't obvious to me.

Dinyar

Re: Tung Oil, almost, but not quite:

Gary Hern (St. Louis)

>First, I want to agee with the other post that stated that you most likely are seeing the scratch pattern left in the piece before you put any oil on it. The circular scratch pattern is the biggest shortcoming that I see in turners. Sanding on the lathe is easy, but you are producing a circular scratch pattern that is next to impossible to hide. The easiest way to fix this is to turn the lathe off and sand with the grain before moving on to the next grit. Power sanding will help with this too, but will still produce a set scratch pattern. While 400 grit is probably fine enough, the scratch pattern is still visible with the naked eye when the surface is wetted. Another way on hard woods like cherry is to take it to finer grits. While the scratch pattern is still there, it will not be as noticeable. I'd suggest turning the lathe off after you sand through that grit, then using the same grit, simply sand with the grain, which in bowl orientation is 90 degrees to the rotation of the lathe. If you have good lighting, you should be able to see the scratches left from sanding when the piece is wetted with water or oil. Question, are you thinning the tung oil when using it for wet sanding? If you are using it at full strength, chances are that the sand paper is not being allowed to do it's job. The thick oil will cause the paper to "float" and not cut. To make wet sanding the most efficient, the lubricant needs to be thin enough to help remove the waste from sanding. Wet sanding with oil will create a slurry, no matter the thickness, and this can help fill small deformities, but it will not build a finish quick enough to hide sanding scratches from 400 grit.

Personally, after sanding on the lathe to about 400g or 600g, I dismount the piece, and hand sand, then apply the oil and hand sand it into the wood, not using a circular motion but rather a linear motion from foot to rim and back. At these grits, you should not see the scratches when doing it this way.

Good luck and don't give up. It really isn't that much more work and you won't regret the extra effort that you put into it.

Foiling phantom scratches

Bob Hackett

>You often hear that some turners spend as much(or more) time sanding and finishing a piece as they do turning it.I think you`ll find that as your turning skills progress this only becomes more of a fact.

I usually tell folks to use the vac and a brush between grits.Brush it hard enough to get all the stray grit out of the grain if you`re using open grain woods like oak or ash.Wet the piece every so often with water between grits.This will bring the scratches up along with the grain.You can also reverse the rotation of the piece afew times so you`ll be sure to cut the grain instead of laying it over if your paper gets dulled.Lastly,I would wet the piece,dry, hand sand with the grain with the finest grit you plan to use before burnishing just to get the last bits of scratches and raised grain.

If all else fails,get Mike Schwing to come to your house and finish it for you.Look at his figured maple bowl above to see what I mean.

Mainely,Bob

Re: Tung Oil, almost, but not quite:

TDaniel

>David, Buddy now has a velcro snding mitt and he works cheap. A butter cookie will get you about 2 minutes of sanding from him. He has to be home before dark though. No other info to pass on, Gary and Bob have pretty much said it all.

TD

So butter cookies is the solution... Lol

David Hammond, in Powder Springs GA

>Terry, I might take you up on that deal - I just need to pick up some butter cookies, then maybe the scratches will go away. :o)

Thanks guys for the responses, all of this really helps - and I'm certainly not going to give up! I think taking the peice off the lathe, and doing some hand work should really help.

Also, I wanted to clarify a little here: I "finished" the cherry bowl I was talking about, months ago - sanded with tung oil, and about one coat of oil on the peice. It sat for months, in a box, then on a shelf, before I took it out to work on it again. I made a point of inspecting the surface before I started again, for scratches. Between the slurry, time, rubbing and handling of the bowl, I could not see any circular sratches. The finish was very low luster then, so maybe the lines were there anyway. But, now, after more oil, the oil seems to have taken on circular scratches, small and fine, but they're there - they look like they're in the oil, coming from how I applied the oil - on the lathe - but maybe not. Obviously I need to keep working on this - thanks for all the info guys!

Sorry it took me so long to reply, my pc went nuts last night...

David

Re: Tung Oil, almost, but not quite:

David Hammond, in Powder Springs GA

>Thanks Gary for the response. I've been using Watco, without any thinner - but I do think adding a thinner would help, as my slurry does get thick, and the slurry starts building up in small amounts, on the surface of the bowl. When it does build up I stop and wipe it off before moving on to higher grits though. I used up the Watco I had, and have switched to Waterlox for these finishing coats. The Waterlox is much thicker, and I have thinned it with mineral spirits - is this ok? What would you suggest to thin the oil with? I think I'll try applying the next coat of Waterlox, thinned, off the lathe. If I can't get rid of the scratches, I guess I'll be sanding through my finish and starting over at some lower grits. I have been reversing the lathe between each grit. Well, I have finally gotten some good lighting at the lathe, so I guess I need to get to work!

Thanks.

David

Re: Scratches after Tung Oil

Ron Sardo from PA

>I usally change sandpaper before it gets a chance to wear out. Think about it, how much are you really saving? Fresh sandpaper cuts quicker so less time is spent sanding. Now if you have to resand because of missed scratches, it now costs even more.

Worn Sandpaper...

Peter Teubel

>I can only offer you the method I actually use (power sanding, of course). For bowls up to 8" in diameter, I use one 3" disc of each grit for the inside and outside...then discard the disc. For bowls bigger than 8", I use one 3" disc for the inside...disgard...and use another 3" disc for the outside. I then use another 3" disc for the bottoms after vacuum chucking, although that disc will last for two bowl bottoms. This applies to ALL grits used.

Yes, I go thru alot if 3" sandpaper discs (minimum 6 per bowl), but I find it the quickest, most cost effective way of production (i.e. sanding time is minimized).

Thinning the mix is good

Dominic Greco in Richboro PA

>David,

Gary is dead on when he says that you should be thinning the finish when wet sanding. For wet sanding really open grained, or problematic woods (like walnut), I use a mix Russ told me about. It's 50 varnish and 50 mineral spirits (or any thinner).

Bob's comments about vacuuming between grits is also great. When wet sanding to Russ' regimen, I wipe the bowl off in between grits with a clean ragged soaked with thinner. I also use my air hose to clean it off. I'm trying to remove excess swarth (dust and finish mixed) that hides these scratch lines. It also helps to make the next grit work better without getting clogged as fast.

Another tip is to have the proper lighting. The proper lighting will help you spot scratches long before you're ready to finish. Check out Fine Woodworking's latest issues for tips on this.

Good luck,

Dominic

Re: Lighting

David Hammond, in Powder Springs GA

>Thanks Dom, all this advice is much appreciatted. I have just gotten some good lighting around the VB: I couldn't decide how I wanted to light the workspace around the lathe, without spending an arm and a leg (maybe both legs). But, my Mom and Dad happened to be in Linin' & Things (of all places) and found a clearanced floor lamp and desk lamp, both with a flexible arm on the head of the lamp, for nine bucks! I never even considered floor lamps, but they're working great! If they get in the way, I move 'em, for roughing and such. But when I need them I can put them right where I need them, and adjust the flexible arm easily. Cheap is so nice, when it works!

David