Wet sanding on the lathe

[Bill Jobe]

Can you wet sand with mineral spirits on the lathe with a rag wet with mineral spirits in one hand and sandpaper in the other?
I've done some reading elsewhere about wet sanding with mineral spirits but I think they were talking about horizontal surfaces and creating a slurry. Can't do that on a vertical surface, but is there an advantage of sanding as such?

[John Keeton]

What finish do you intend to use?

[Bill Jobe]

Tung oil finish.
Do you have a better finish in mind for walnut?
It is currently bare wood. I want a finish that pops, that really brings out the grain.

[Bill Jobe]

My very first big one on the 766. I have 3 4-5" kiln dried slabs 6' long I intend to make (shallow) bowls and platters with.this piece is a very shallow 19" bowl.

[Bob Bouis]

You can wet sand on the lathe, but why use mineral spirits? If you're aiming for an oil finish, use the oil.

[John Keeton]

Nice piece of wood! I would start wet sanding with the finish at 220. That will build a slurry that will fill the grain. Frequently wipe it across the grain with a shop towel and if it gets too gummy add a little MS to a bit of the finish to continue thru 320 and 400.

[Bill Jobe]

Nice piece of wood! I would start wet sanding with the finish at 220. That will build a slurry that will fill the grain. Frequently wipe it across the grain with a shop towel and if it gets too gummy add a little MS to a bit of the finish to continue thru 320 and 400.

That's exactly where I just quit sanding, so...just right.
I usually don't dilute the TOF, but will I get deeper grain to come up if I do so on the first coat?

What do you use on walnut? I want deep grain and killer gloss.

[John Keeton]

Bill, folks use a lot of terms interchangeably. I prefer to use "grain" to refer to the direction of growth, evidenced by pores and growth rings with alternating hard and soft wood. Figure, on the other hand, is usually referred to as the undulating grain in certain pieces that when cut creates chatoyance. This occurs because by cutting across the "waves" one exposes alternating long grain and end grain. Often, this is referred to as curly, tiger, quilted, etc. You have some of that in your walnut. IMO, if one wants to preserve chatoyance, then oil is avoided. However, using oil will enhance the contrast of the undulating grain by darkening the end grain because it will soak up more of the finish/oil than will the long grain.

Wood can also have color created by spalting or fungus, mineral streaks, Ambrosia beetles, and other insects. Often streaks of color are just a part of the naturally occurring coloration in certain woods. I hear people refer to this as "grain" or "figure", but I typically do not associate those terms with color.

So.... if what you are wanting is "deep figure" then you need to decide between the chatoyance or the contrast created by an oil finish. For me, I like the contrast moreso than the chatoyance, but that is my personal preference. To that end, I would do just what you are doing.

For "killer gloss" one must have both a flat, smooth surface and closed pores. Wet sanding with the oil finish will go a long way toward filling the pores, especially if you will push the slurry into the pores by wiping it across the grain and letting the finish set some between grits. Then, it is going to take multiple coats of finish, applied carefully, with wet sanding of the finish a couple of times along the way, and for me, just prior to buffing.

[Marvin Hasenak]

A good article to read by Frank Whiton, https://www.firearmsforum.com/firearms/article/3037 I use a similar method on the lathe when finishing any wood that has large pores like walnut.

[Dennis Ford]

I have wet sanded with mineral spirits on the lathe when I turned "fat lighter" pine with lots of resin. Normal sanding of this wood is impossible.

[Doug Hepler]

Bill,

Yes, I have a better finish for walnut. There are lots of things to sort out here first.
(1) What product are you using? Some "tung oil" is oil/varnish blend. They might give you enough build to get the gloss you want. Pure tung oil will build but the process takes many coats with long drying times, and you still may not get the finish you want. You can pop the grain with any oil or oil/varnish mix. I just use linseed oil.
(2) If you want to fill the pores you can use French polishing or a pore filler. I use French polishing. French polishing will give you a brilliant gloss. Use blonde shellac because a few coats of regular shellac may darken the walnut more than you want. When finishing mugs, I have experimented with two-part epoxy like West System or Max Clear. That puts a "bar top" or decoupage coating on the vessel. Cured epoxy can be scraped and polished like varnish and it is as clear as water. The vessels finished with epoxy look like ceramics. I have also used acrylic varnish like Polycrylic. It adds very little color and dries in 2-3 hours. 600-800 grit paper followed by wax will give you a very glossy finish.
(3) If you want to rub out the finish (you probably will not need to) use pumice in mineral oil and/or rottenstone in mineral oil. Just mix a bit of the powder with enough oil to make a smooth slurry, put it on a pad and rub away on or off the lathe. Just be sure that the substrate is smooth without pores because the grey pumice will collect in any depressions.

So -- no wet sanding is necessary

Doug

[Steve Bistritz]

Related question.... I have used Fornbys "tung oil" and sanded with it to fill pores and if I use it on lighter woods the pores turn dark and seem to stand out because of it...I have tried boiled linseed oil but it turns white when sanded...not cured enough??? Can you explain french polish???


Bill,

Yes, I have a better finish for walnut. There are lots of things to sort out here first.
(1) What product are you using? Some "tung oil" is oil/varnish blend. They might give you enough build to get the gloss you want. Pure tung oil will build but the process takes many coats with long drying times, and you still may not get the finish you want. You can pop the grain with any oil or oil/varnish mix. I just use linseed oil.
(2) If you want to fill the pores you can use French polishing or a pore filler. I use French polishing. French polishing will give you a brilliant gloss. Use blonde shellac because a few coats of regular shellac may darken the walnut more than you want. When finishing mugs, I have experimented with two-part epoxy like West System or Max Clear. That puts a "bar top" or decoupage coating on the vessel. Cured epoxy can be scraped and polished like varnish and it is as clear as water. The vessels finished with epoxy look like ceramics. I have also used acrylic varnish like Polycrylic. It adds very little color and dries in 2-3 hours. 600-800 grit paper followed by wax will give you a very glossy finish.
(3) If you want to rub out the finish (you probably will not need to) use pumice in mineral oil and/or rottenstone in mineral oil. Just mix a bit of the powder with enough oil to make a smooth slurry, put it on a pad and rub away on or off the lathe. Just be sure that the substrate is smooth without pores because the grey pumice will collect in any depressions.

So -- no wet sanding is necessary

Doug

[Doug Hepler]

Hello, Steve

I'm happy to respond to your questions. My guess (no more than that) is that the oil is darker than the wood and that sawdust in the pores looks dark because the surfaces of the sanding dust are irregular and do not reflect light back out at you. I tried the method of sanding in a finish years ago and did not like the result. Unless the wood is very porous I prefer to smooth it with multiple coats, which is where the French polishing comes in.

I have never seen BLO act the way you describe. Let me explain how and why I pop grain with BLO, which will also explain why I have never seen that phenomenon. Oil accentuates grain pattern because it penetrates wood to different degrees. For example, grain rising to the surface has pores that the oil can penetrate more, while grain that is parallel to the surface basically just gets wetted by the oil. I apply BLO and let it penetrate for a few minutes to an hour. Then I scrub it off with a clean rag. After that, I let it dry at least overnight. A thicker coating of oil takes longer to dry and can take days. BLO never hardens into a film, so why leave it on the surface? (Pure tung oil and oil/varnish blends will eventually harden into a film, but I'm not interested in that property.)

Now to the French polishing. There are many ways to do this and many sites on the web describing it. I use about a 2 lb cut of shellac. Zinsser Seal Coat is a great product and I often use it. (Sometimes, for very light wood, I go for ultra-blonde flakes and mix it myself.) Take two pieces of hard finished cotton cloth (e.g., denim from washed bluejeans). Fold one piece into a small pad about the size of a silver dollar. Wrap that in the other piece and tie it with string to make a bundle, sort of shaped like a mushroom. The stem of the mushroom should be long enough that you can grip it easily with your fingers. That is your application pad (called a fad, don't ask me why).

OK. Pour about 1-2 oz of shellac into a wide-mouth jar and saturate the pad. Pour a little BLO onto a separate dish. When the pad is saturated, wring it out a bit so that its wet but not really dripping. The idea is to have a reservoir of shellac inside the pad. Start your work piece spinning slowly, probably as slow as it will turn. Apply the shellac evenly with the pad. Don't press too hard. At first the shellac will just flow on and the pad will slide smoothly. You can see when it starts to dry. Squeeze a little more shellac out of the pad and continue. Here's where the "art" comes in. Eventually the shellac will start to grab. Now dip the pad in the BLO. You just need a drop. It will act as a lubricant and let you polish the surface of the shellac without grabbing. At this point it should look nice and shiny, even if the pores are not filled. Put the pad back in the jar to soak. Let the surface of your turning dry an hour or so (or more) until it is hard. Then repeat the process until you have the surface you want.

Usually, you will have a high gloss surface. If you like you can gently sand it with 300-600 grit paper and then apply a coat of wax.

Hope this helps.

Doug

[robert baccus]

Just a few comments learned the hard way. Forby's Tung oil finish has no tung oil in it??? Your description of a French polish is Very new and unique and wrong. The real method used a tampon, shellac, mineral oil and acahol and much elboe grease. Google it up--beats opinion every time. A french polish is probably the prettiest finish in the world if labor is plentiful.

[Doug Hepler]

Dear Robert Baccus

You wrote <Google it up--beats opinion every time.> It's not opinion. It's how I do it. I have done this procedure about 20 times over the years on turnings, and a similar process for table tops. We are now hijacking the OP's thread and I will not respond further.

Doug

[Steve Bistritz]

Thanks so much Doug!!!!!!

[Bill Jobe]

Bill, folks use a lot of terms interchangeably. I prefer to use "grain" to refer to the direction of growth, evidenced by pores and growth rings with alternating hard and soft wood. Figure, on the other hand, is usually referred to as the undulating grain in certain pieces that when cut creates chatoyance. This occurs because by cutting across the "waves" one exposes alternating long grain and end grain. Often, this is referred to as curly, tiger, quilted, etc. You have some of that in your walnut. IMO, if one wants to preserve chatoyance, then oil is avoided. However, using oil will enhance the contrast of the undulating grain by darkening the end grain because it will soak up more of the finish/oil than will the long grain.

Wood can also have color created by spalting or fungus, mineral streaks, Ambrosia beetles, and other insects. Often streaks of color are just a part of the naturally occurring coloration in certain woods. I hear people refer to this as "grain" or "figure", but I typically do not associate those terms with color.

So.... if what you are wanting is "deep figure" then you need to decide between the chatoyance or the contrast created by an oil finish. For me, I like the contrast moreso than the chatoyance, but that is my personal preference. To that end, I would do just what you are doing.

For "killer gloss" one must have both a flat, smooth surface and closed pores. Wet sanding with the oil finish will go a long way toward filling the pores, especially if you will push the slurry into the pores by wiping it across the grain and letting the finish set some between grits. Then, it is going to take multiple coats of finish, applied carefully, with wet sanding of the finish a couple of times along the way, and for me, just prior to buffing.

I'm experimenting on a smaller bowl I hadn't finished yet.
I just wet sanded with 320 and tof/mineral spirits. Do I sand and wipe more than once before letting it dry?

[John Keeton]

Once per grit for me, but it is critical that all sanding scratches from a prior grit are removed before proceeding further. I spend progressively less time as I move up thru the grits with the most time at 150 dry. I don't wet sand until 220.

[robert baccus]

There are some great articles on U-Tube concerning French polishing done the traditional way. These go into detail on materials and techniques. I have a copy of a book written in the 1600's by the director of wood finishing for Louise 14th. Covers this and finishing with wax, shellac, oils and lacquers. There were many new materials for finishing as well as woods from the new world.

[John K Jordan]

...Now to the French polishing. There are many ways to do this and many sites on the web describing it. I use ...


Doug, very nice write-up. This is much the way I do french polishing except I never tried denim, I use thin cotton with an extra wad inside, tied at the top as you mentioned. I use a pad like this for rubbing with pumice and rottenstone too as learned from a gun stock finishing article.

I also like your explanation of how the grain orientation affects the appearance of wood when oil is applied which well describes the effect of oil on figured wood. I finish many of my pieces with oil using the same technique you described but I usually use "danish" oil instead, which probably has a BLO base. I occasionally repeat after the initial drying, but just wipe on, wipe off with no soaking. This can be buffed to a shine if desired without a building up a layer on the surface or filling the pores. I often prefer a soft sheen instead of a gloss.

BTW, I do use gallons of BLO, but around the farm instead of on turnings - rake and wheelbarrow handles, barn doors, wood benches and steps, etc., brushed on thick and left to dry. It works wonders for wood left in the elements.

JKJ

[Hayes Rutherford]

Still another description of French polishing that is pretty good. Somewhere in the article is a photo of the "vapor trail" that is left when things are happening right. http://www.frets.com/FretsPages/Luthier/Technique/Finish/FrenchPolish/frenchpolish1.html

[ron david]

There are some great articles on U-Tube concerning French polishing done the traditional way. These go into detail on materials and techniques. I have a copy of a book written in the 1600's by the director of wood finishing for Louise 14th. Covers this and finishing with wax, shellac, oils and lacquers. There were many new materials for finishing as well as woods from the new world.

do you do any french polishing at all ?
ron

[Jay Mullins]

Thanks for taking the high road.

[robert baccus]

No longer like a lot of things. I Perfected my techniques in lacquer finishing and can duplicate (?) a french polish on the lathe in a small fraction of the time using newer materials and techniques. Many of these I learned finishing old jalopies & show cars in my misspent youth when lacquer was the only great finish available. It is very easy, forgivable and repairable and very easy to "rub down" to any gloss desirable all on the lathe. I only touch up the bottoms and sign them after dismounting. Interesting--Sean Connery was discovered while doing french polishing on coffins in London. May be a way to Hollywood.