French polish, was Ebony finish, round two

[Stéphane Collin]

Hi John.

I'd be interested in hearing your detailed process of French polishing.
Everybody I asked seems to have his own method which can vary wildely from
another, even if inherited from a branch of tradition.  I find it most
interesting.

Here is mine, for your comments.

Up till now, I found for myself that a lot of problems with French polish
come from insufficient pore filling. If this was not done intensively
enough, the shellac nicely polished is soon destroyed by its reaction with
the porous wood underneath and the alcohol or oil or void that is still in
there.  Of course, it depends on the pore size of the wood.  Most of my work
is on Rosewood and Mahogany, who both have quite open grain.
For black pianos, I believe I find usually walnut (not sure though) anyway a
much closer grain.  Yet, pore filling seems unavoidable for me.  After fine
sanding the bare wood up to 800 grit (many stop at 240, but I find the
filling goes better when the wood is sanded to 800, also at this level, I
use no water nor oil for sanding and change often the sanding papers), I
stain it with water based anilines black stain (this way, if you look
closely to the end result, you still can see slightly the wood grain, which
I find nice).  I let dry for a few hours, and then start filling the pores
by rubbing silky quality pumice stone with an alcohol filled rubbing pad
(wool inside, covered by a quite thick woven cotton veil : must be thick in
order 1° not to tear prematurely with heavy rubbing and 2° let the kind of
mastic appear between the cotton, mastic made of pumice stone, wood powder
and alcohol, which you get after a little rubbing).  The pumice I put in a
lady's pant which I tap on the surface gently, so to put minimal pumice
quantity on the surface (some cover the surface completely with pumice, but
this didn't work for me).  Not too much pressure in the beginning, and not
too much pumice stone either.  If the pumice stone clogs on the surface, I
refill the pad with alcohol.  I don't rub more than 30 cm² at a time (or the
alcohol evaporates prematurely and I can't control the mastic).  If the
filling is really too slow to happen, I add minimal shellac to the pad in
order to facilitate the mastic to appear.  Only on the first refilling, then
no more (or you get a mess, and if this happens, you're up to sanding
again).  In time, more pressure, and sometimes add very few pumice.
Usually, adding three times pumice on the work will do.  The movement is
important : rounds (not eights) with the arm in a position such that the
maximal pressure happens across the grain.  In time, the rounds become more
oblong toward straight strokes in the direction of the grain.  Here, in
time, appears already a nice shine (many are not after any shine at this
level of work, but I noticed that if I go on until this shine, the polishing
after is much facilitated).  To see all this happen, you need to look
against daylight (not direct sun, of course, nor artificial light).  I
consider the pore filling finished when against the daylight you can't see
any pores anymore, AND the surface is shiny.  Then let overnight and see
what is left the next day.  Sometimes, it stayed ok, but with rosewood, for
sure, I have to redo it all over again (because wood porosity has slicked
all my work).  Usually, after the second time, it is ok, but it might need a
third time.  When the pore filling is done, I start applying the shellac
with another rubbing pad : still wool inside, but a finer cotton veil
outside.  I use few of everything : just turning the can of shellac upside
down with the wool on it, then immediately back, then about the same
quantity of alcohol, then mix those into the wool pad by squeezing it, then
put the cotton veil on it, then put one or two drops of Sumatra oil (very
colorless and not that fatty) on the veil.  Again, no more than 30 cm² at a
time, first large movements with little pressure, in order to spread the oil
on the whole surface.  Then small eight figures in order this time to roll
the shellac in every directions, avoiding that the rubbing pad ever stops
moving on the work (which would cause a disaster).  I use few of everything
because I believe that the nice shine comes when the pad is drying.  So if
the pad was full of shellac and alcohol, it would take ages before the pad
doesn't leave traces anymore, and I don't see the purpose.  In time, the
eight figures progressively get larger, and end up in long straight strokes
in the direction of the grain.  Here, I quickly obtain the finish I am
after.  Alas, it doesn't stay so.  Again, after one or two hours, some of
the shellac is absorbed by the under layer.  But then, same process again,
and usually after three or four times, I have a stable and superb finish.
Let dry for one or two weeks (not less) and then, much of the oil used in
the process will have come to the surface, leaving little spots ruining the
finish again.  Then this oil is taken off with a third pad : still wool
inside, and an old but clean used cotton veil over it (a new one would
scratch the finish).  This I fill with absolute minimal quantity of a
mixture of alcohol and benzene.  The pad must not be wet, only humid, which
you feel best with your lips.  If too humid, you would ruin the finish.  And
then, with a very quick and light movement, long strokes in the direction of
the grain (no more turning, or you make new traces).  Oil gets off, and the
beautiful end finish appears.  Not manipulate until three weeks at least.
I'd be happy to have comments and variations.

Best regards.

Stéphane Collin.


One thing I would warn against is French polish on a maple substrate. 
Thankfully very few makers in Europe used maple veneer for black 
pianos but Steinway were an exception and I am unfortunate enough to 
have two of these to finish.  Like beech, maple will not hold a 
finish for very long without problems in my experience.  If there's a 
secret I'd love to hear it.

JD