French Polishing on a Wood Lathe

As my friends and collectors know, I am passionately committed to environmentally friendly finishes - what the FDA calls "GRAS" ("Generally Regarded As Safe.")  For me, that usually means using pure, food-grade walnut oil on all pieces intended for direct food contact. For other work, I generally favor my own beeswax and walnut oil polish, the Real Milk Paint Company's "Dark Tung Oil" or Tried 'n True's "Original" finish.  All of these products produce surfaces ranging from mat to a warm satin sheen, largely depending on the wood.  "Hard" hardwoods like ash, oak, beech, and hard maples, when properly dried, can be sanded and polished so that a touch of walnut oil produces a bright, almost semi-gloss, finish.  While the softer hardwoods like walnut and birch take on a softer mat glow.

Some work, like the candlestick set shown above, however, cries-out for a high-gloss finish.  Problem is: most glossy finishes are anything but eco-friendly.  (Yes, I know: after 72 - or so - hours, just about any commercial finish is considered "safe," but until then exposing oneself to mineral spirits and other VOC's is not something I care to do.)

Another technique, familiar to woodturners - especially pen turners - is called "friction polishing."   Friction polishing is a fairly simple technique that uses a shellac-based finish that is applied directly via a rag held against the spinning workpiece.  As the finish is applied, friction-induced heat dries it almost instantly.  Although comparatively easy, friction polishing isn't foolproof.  But with a little practice, one can obtain a pretty decent gloss finish.  The nice things about friction polishing are (a) it's quick and (b) shellac is a natural product that, when dissolved in grain alcohol (I use 190-proof from the liquor store), fits into the GRAS category. (Shellac is also used as a pill coating, btw.)

While friction polishing can produce a pretty good finish, there are times, like with this walnut platter, when something even better is desired.  At times like that, I turn to the time-honored technique known as "french polishing."  Please note that I called french polish a "technique" - not a "product."  That's because, contrary to its name, french polishing relies on the gradual buildup of hundreds - if not thousands - of micro-coats of shellac, oil and other products to obtain what is widely considered the most beautiful way to finish highly figured wood.

The basic technique, which was more-or-less settled by the 18th century, is accomplished by using a wadded cloth pad called a "rubber" to hand rub the micro-coats of shellac and other materials into the wood surface.  This is done in continuous circular and figure-8 patterns.  Any resulting streaks are then "spirited off" with a fine application of alcohol - also applied with the rubber. The process is repeated - in various forms - 12 to 15 times over a period of two weeks to a month until the final finish at last emerges.  (Fair warning: french polishing is anything but easy - and it sure ain't fast.  Ask a luthier to french polish your custom guitar and you just added $1,500 - $2,000 to the tab and another month to your wait time.)

As we will see, the classic process is indeed labor intensive.  The basic process works like this:  the workpiece is first sanded to at least 600 - 800 grit to remove all toolmarks and all but the finest micro-scratches.  Such fine sanding is needed because the french polish will magnify even the smallest defect(!)  Next, we use our rubber to build-up a base coat shellac over 6 - 8 "bodying sessions" where we apply 2 lb cut shellac using continuous, overlapping circular and figure-8 motions. We can do 2 - 3 of these "bodying sessions" a day allowing 3 - 4 hours for the previous coat to dry and harden.  (We should note that shellac takes weeks - if not months - to fully "harden."  But 3 - 4 hours is sufficient for our purposes at this stage of the game.)  After 3 - 4 days, having built up a reasonable shellac base, we fill the wood grain by rubbing the piece down as before, except now we add a drop of oil (I prefer walnut because I believe it gives a slightly harder final finish) and a dab of 4F pumice. (You can actually hear the pumice working with the shellac and wood fibers to fill the grain.  Kinda neat, really.)  We then set the piece aside for 2 - 3 days to harden-up.

Now the real work begins.  Using our rubber and an equal amount of 2 lb shellac, (for me) grain alcohol, and a drop of walnut oil, we do the actual french polishing.  This consists of another 6 - 8 sessions (at 2 sessions a day separated by 4 - 6 hours.)  After each session, we "spirit-off" any streaks with our rubber moistened with a few drops of our grain alcohol.  By the 3rd or 4th day, our workpiece shows some minor unevenness, which we level off with 800-grit sandpaper soaked in walnut oil.  After another "spiriting-off,"  we follow-up with another 3 - 4 french-polishing sessions - this time with a 1 lb cut of shellac.  (Almost done.)  By now, we set our workpiece aside for another 3 - 4 days to allow the finish to stabilize and harden before a final sanding at 1200 - 1800 grit (again with walnut oil lubricant.)  One more spiriting-off and we set the piece aside for 1 - 2 WEEKS to really harden.  As a last step, I give the piece a final polishing with my home-brewed walnut oil/beeswax/rottenstone polish. E voila'! (I know of one artisan who uses a high-grade automobile polish - but since it ain't eco-friendly, I don't.  No worries - to each his own....) 

Fortunately, we woodturners can make things a little easier by using the lathe, rather than hand-power, at most stages of the game.  One well-respected turner also advocates using thin CA glue as a base/grain-filling coat instead of shellac.  (I have no experience with that technique, but it sounds promising.)  In practice, I've found using the lathe makes each session easier, at least through the "rough-leveling."  But it still leaves an uneven finish that must be rough-leveled by hand, as described above. (One could try power buffing, but I'm not crazy about it on a shellac finish.)  I also find I get best results by doing the last french polishing sessions,  with 1 lb shellac, by hand - with the final hand beeswax/walnut oil/rottenstone rubdown.

Candidly, I only invest this amount of time for special pieces like those shown.  It is a lot of work, but the payoff - both in results and personal satisfaction - is more than worth it!

I hope you agree.

The Misunderstood Skew, Part 2

The previous post on the "Misunderstood Skew" drew some positive Facebook feedback, so I thought it might be good to follow-up with a little bit of technique.  This post won't go into a lot of detail, but will hopefully whet the appetite for a video.  In this post, we'll look at tool selection, (including my personal preferences), talk about how to sharpen the skew (and keep it sharp!) and lastly the different kinds of cuts that make the skew such a versatile tool.

Tool Selection
The skew chisel is simply a straight tool sharpened at one end so as to present an angled ("skewed") or curved cutting surface to the workpiece.  The bottom of the angled/curved edge is called the "short point" while the top is referred to as the "long point."  Skew chisels come in three cross-sections: round, oval and flat.   The round skew is basically a round rod with a skew cutting surface ground into the working end.   Although some love it, the round skew is really a specialized tool with limited applicability in my experience.  And since this is a more general conversation, we'll limit the remainder of this discussion to the flat and oval skews.
 

The oval skew, shown on the far right, is ground with slightly rounded sides.  The theory being that the oval cross section makes the tool a little easier to control.  In practice however, I find the oval skew blade a bit light, prone to flexing and more difficult to sharpen.  Many turners swear by the oval skew, but because it tends to be heavier and stiffer in use, I prefer the flat tool.  I leave it to the reader to determine his/her own preference. 


Sharpening
As one reader correctly pointed out, the skew needs to be sharp to be effective.  I think the term, "scary sharp" is not too much of an exaggeration.  The logic is: a sharp tool cuts easily, cleanly - and goes where you want it go.  A dull tool requires additional force resulting in less (and possibly loss of) control and an inferior workpiece surface.

Sharpening the skew is fairly simple.  After establishing the cutting edge on the bench grinder, we simply hone all four sides of the cutting surface (yes, 4: both sides, then the top and bottom) with a diamond sharpener to the point where the tool will cut hair.  (Sounds tough, but in practice, it's very quick and easy.  After a while, it becomes automatic.)  This honing is necessary because the skew edge is sharpened at a very shallow angle (I sharpen mine at around 25 degrees), and is thus not as durable as, say, that of a gouge.   By honing and keeping the skew sharp, I rarely find myself returning the skew to the grinder.

Cuts

We use the skew to perform five different types of cut: the scraping cut to gently refine a shape, the roughing cut to reduce a square block to a cylinder, the shearing cut to clean-up and/or refine end-grain surfaces, the planing cut to smooth and refine the sides of the workpiece, and the v-cut; plus, what I call "compound" cuts to produce beads (convex shapes) and coves (concave shapes.)


With all of these cuts, I find tool rest height one of the keys to success.  With a gouge, we typically set the tool rest to a height that places the cutting edge at or slightly below the centerline of the workpiece.  But with the skew, I'm most comfortable with the top of the tool rest slightly below the top of the workpiece.  (The exact height is determined by practice.)  The other thing I do is to run the lathe at a moderate speed - rarely going above about 1600 rpms for most work.  A "scary sharp" skew cuts well at moderate speeds and stays sharp longer than if the lathe is screaming.  (Lidded box finials and pens are exceptions, but the key is to be sure you are comfortable in all aspects before beginning work.)

This candlestick was produced almost entirely with a 1" skew chisel using all of the cuts described above.  The exception was that a forstener bit was used to drill a hole in the base, which was turned separately, to help support the candlestick stem.

The Misunderstood Skew

 

The skew chisel is probably the single most versatile spindle turning tool at the woodturner's disposal. In fact, nowadays, I find myself relying on skew chisels for the vast majority of my spindle turning work from roughing cuts - reducing a square block to a cylinder - through subtle concave and convex curves all the way through the finest detail in the most delicate finial.  As an added bonus, staying with one or two implements throughout the project saves time that would be otherwise spent reaching for - and having to sharpen - multiple tools.

No, the skew is not for bowl turning or hollowing-out a vase.  There are other tools for those tasks.  But used for its intended purpose, the skew rewards the turner with flexibility and control difficult to achieve with any other spindle turning tool.

It's interesting that when the subject of skew chisels comes up among a group of woodturners, the reaction is either enthusiastic agreement or strained silence.  The silence typically comes from fear, usually instilled by woodturning "teachers" who managed to convince their students early on that successful skew usage is a mysterious art somewhere to the left of black magic.  Used improperly, the skew can produce spectacular "catches" resulting in (1) scaring the dickens out of the turner and (2) an almost perfect spiral cut along the workpiece - usually where the turner just finished working(!).  But used correctly....   

What makes the skew so intriquing is that it is capable of so many different cuts.  Although each cut requires slightly different skills, if we take each cut individually, mastery is not difficult. I have had beginning pen turners performing near perfect roughing and scraping cuts in a matter of minutes.  I just don't tell them that the skew is supposed to be difficult. I simply show them how to position the tool and they take it from there.

For those interested, Alan Lacer's videos are a good place to start - that is: until I get my own out there ;-) .