|
Creating
a Black Piano Finish
The following
were posted to the DIY Loudspeaker list.
From:
Delwin D Fandrich
Date: Tue, 21 Jul 1998 10:42:35 -0700
OK. About
that "Piano Finish" we hear so much about. There
are two distinctly different finishes being talked about here.
The traditional "hand-rubbed" piano finish and the
more recent "high-gloss" finish. The high-gloss
finish is polyester -- a plastic. Since we don't care for
the look that this finish gives to pianos we don't use it
and I'm not qualified to comment on its application.
The hand-rubbed
finish is usually nitrocellulose lacquer. This material is
quite easy to work with, just remember that it is extremely
flammable -- explosive even -- so take care. It also stinks
and it's not real good for your insides. You will need lots
of ventilation, both to reduce the fire danger and to reduce
the wear and tear on your lungs and your brain.
The following
procedure works for both clear and colored lacquer finishes.
If you are using black, I'd suggest using an automotive acrylic
lacquer. Especially if you want a high-polish finish. Traditional
nitrocellulose tend to look a bit blue or gray when polished
out.
- Surface
preparation. All surfaces must be sanded to a dead flat
finish. We dry sand with an open coat aluminum oxide paper
-- not stearated -- starting (usually) with 120 grit and
working up through every grit to 320. When sanding flat
surfaces the paper is always used with a firm rubber sanding
block. All surface dings, scratches, blemishes, etc., are
filled or fixed after the first sanding with 120 grit. All
imperfections must be fixed before either the stain or the
first coats of finish are applied. (The obvious exception
being with a black finish which can be patched at any time.)
After the final sanding we "break" the edges to
a nice uniform radius using 220 or 320 grit paper backed
up with sensitive fingers.
- If the
wood is an open pore wood and the finish is to be closed
pore, the next step is to pore fill. Pore filler is a silica
base material that is thinned to approximately the consistency
of heavy cream and brushed on both with and across the grain.
Pore fillers can either be applied in their natural color
-- a light creamy tan -- or stained to accent the pore texture
of the wood. Once the pore filler is partially dry (the
surface is just dull) it is wiped or scraped off across
grain. A tiny amount of pore filler will be left in the
open pores of the wood leaving the surface quite flat. Allow
the remaining pore filler to dry for at least 24 hours and
sand the surface lightly with 220 grit and 320 grit dry
paper.
- If the
wood is to be stained, now is the time to do it. We also
stain the wood of pianos that are going black. It helps
later when Johnny runs into the leg with his new toy truck
and chips the finish. There are a variety of different types
of stains available. Books have been written on the subject.
For most amateurs the selection is going to be somewhat
limited to what can be found at the local HomeBase or hardware
store. These are usually oil based or water based stains.
All I can say here is to follow the directions on the can.
- After
the stain is dry apply the first coats of finish material.
You can use sanding sealer if you wish, we do not. Sanding
sealer is simply lacquer with some additives blended in
to make it easier to sand. If you've done your prep work
well you won't have to do that much sanding anyway and lacquer
without the added stearates bonds better and is more durable.
(Note: If I were putting a black finish directly over MDF
or particleboard, I'd first spray on a coat of black or
dark gray automotive primer. These are very heavy bodied
filling primers designed to fill in rough metal work and
leave a fairly smooth sanding surface. It might take two
coats.)
We spray three coats of lacquer straight over the stained
wood surface. Allow this to dry (we allow 24 hours) and
wet sand with 320 grit wet-or-dry paper on a firm rubber
sanding block. Don't over do this. You're only trying to
knock off the high spots here. Lacquer chemically bonds
to lacquer so you don't need to "rough-up" the
whole surface. You're getting rid of raised grain, dust
particles, etc. (You didn't get any runs in the vertical
surfaces, did you? If so, sand them out also.) What you
don't want to do is sand through your nice new surface into
the stained wood.
- Spray
three more coats of lacquer on the surface. You're more
experienced now so you won't get any more runs, right? Again,
allow 24 hours of drying time and wet sand with 400 grit
paper still on a firm rubber block. This time you want to
sand the surface pretty well flat. Always sand with the
grain and be extra careful around the edges.
- Spray
on three more coats of lacquer. This time let the surface
dry for at least three days. Wet sand, starting with 400
grit paper and working through 500, 600. If this is to be
a "hand-rubbed" finish stop here. The final rub
is most easily done with plastic wool sheets (the white
kind without any built in abrasive) and pumice or rottenstone.
If you can't easily find these, good old Ajax will work.
So will automotive rubbing compound.
If the finish is to be more highly polished, continue sanding
through at least 800 grit. Now switch to polishing compounds.
We use 3M, but McGuires (sp?) is more commonly available.
Visit your local auto paint store. There are about a million
different compounds available and I don't even pretend to
keep up with them. Find someone at the store who knows what
they sell -- if you can -- and ask. The final polish will
be done with a random orbital buffer. These might be available
for rent. Otherwise, check Sears and/or head back to your
local auto paint store.
The above
is not intended to answer all of your questions about finishing
wood. It's a complicated subject, but it's not an impossible
subject for one who has already figured out how to build a
speaker system. If all of this whets your appetite for fine
finishing, might I suggest two excellent books:
- Understanding
Wood Finishing by Bob Flexner (Rodale Press), and
- Spray
Finishing by Andy Charron (The Taunton Press).
Achieving
a fine finish on your work is not all that difficult. It does
require some knowledge of the the materials you use and the
proper techniques used to apply them. And some patience. Good
luck.
Del
Del Fandrich
Piano Designer & Builder Hoquiam, Washington USA
From:
Keith A. Lahteine
Date: Sat, 18 Dec 1999 12:27:18 -0500
Dear List
Members :
I'll tell
you how I apply a gloss black, or any color for that matter,
painted surface.
Before I
got involved with loudspeaker systems, full time, I ran a
cabinet shop and built quite a few specialty furniture items.
As well as build the items I had to finish them. About 25
years ago I had a friend who was employed as a yacht painter.
Most of the yachts he painted were wooden. He worked for a
very high priced "Yacht Yard". One of the Crosby
families from Osterville on Cape Cod. I used to marvel at
the finish he achieved with a brush. There was no way you
could apply quite as durable a finish by spraying. I'm in
no way against spray painting but for M.D.F. it would be close
to impossible to tell the difference between a brushed and
a sprayed finish. Brushing, for one thing, puts down a much
thicker and more durable finish, not to mention much less
costly. People get so hung up on automotive type finishes
they forget or don't appreciate the fact that your working
with a cabinet not a car. No matter what type of final finish
you choose the preparation work is very important. I'm just
trying to stress that you don't need to use a spray finish
to achieve a very good result. A a matter of fact brushing
will get you a much thicker, more protective, finish. I always
recommend oil base paint as well. It might just be me but
I've never seen as good a finish achieved with latex paint.
For a prime I like something like a white shellac such as
"BIN" or "Stain Kill" either of these
can be darkened for the black finish paint. If you leave it
white it's a little harder to cover. Put the prime on before
you do any filling. Trying to use something like "Spackle".
Any fill on bare M.D.F. may cause the fill to shrink a bit.
It works a lot better on the primed M.D.F. "Spackle"
comes in two weights, regular and light. The lighter is just
that, a little lighter. It will, also, dry more quickly than
the regular consistency. The light sands more readily as well.
This might be something to consider if you plan on using a
lot of it. In any event it, usually, takes two applications
of fill to complete the job. An initial sanding with about
a 120 grit followed with a 220 grit is about right. I like
to sand everything with, either, finish sander or a random
orbit and about 120 paper . After this the prime is then applied.
When the prime is dry lightly skuff it with 220. I like to
wipe down the piece after sanding with a rag or paper towel
dampened with alcohol or water. The alcohol dries a lot quicker
than the water. After this your ready to apply the "Spackle"
fill. A regular putty knife is, usually, all that's required.
The reason I suggest two applications are in case any deep
or extensive fill areas are encountered it can take a couple
of fill applications to cover them. Sand any fill areas with
a wood block to maintain flatness. Depending on how much leveling
you have to do, either, 120 or 220 paper is desired . In any
event finish with the 220 as a final prep. for finish paint.
Remember the last step before your finish paint is that wipe
down with the damp rag. Picking the proper finish paint is
a very important step.
A few years
ago I worked for a cabinet company in "Palm Beach County",
Florida. Whenever a painted finish was requested there was
only one place that was considered for supplying the paint.
The "Benjamin Moore" store. There is No.1 in paint
and No.2 is a long way back. The "Benjamin Moore"
is that good. They have an oil based finish called : "Impervo"
. This comes in a satin or a gloss finish. I use the satin
finish no matter whether I want a gloss or a satin in the
end. I believe it takes three coats of finish paint to do
an adequate job. Each coat is then lightly sanded with a 220
grit paper or a 400 (wet or dry) before the next coat. If
a final gloss finish is desired the third coat of paint is
then followed with a few coats of gloss urethane. As a matter
of fact even if your after a satin finish the gloss urethane
is a good idea. The final coat of urethane can then be followed
with, either. pumice or rotten stone to achieve the satin
finish. After everything is dry a good coat of paste wax will
preserve the whole business.
Good Luck
: Keith
P.S. Here
are a couple of tips. For brushing a good oil based finish
use a good "China Bristle" brush. About two inches
is good. Surprisingly those, inexpensive, foam brushes work,
pretty, well too.
From:
Ed Heath
Date: Fri, 12 Jan 2001 12:47:22 -0500
Flat black
spray paint and 0000 steel wool, then several coats of spray
polyurethene, buffed between coats, will produce a finish
that can't be told from the labor intensive real thing. You
can determine the amount of gloss by choosing the grit of
the wet dry sandpaper that you use for the last coat of clear
Poly. Use High gloss, because it is harder, and you can bring
the gloss down to wherever you choose with the black sandpaper.
Use paint thinner with the wet/dry sandpaper, rather than
water. An initial coat of thinned low density (Red Devil)
spackle. It sands easily, and will fill all of the irregularties
in the surface. Block sand the spackle.
Date: Fri,
12 Jan 2001 21:17:31 -0500
It is possible
to give this treatment as much depth as wanted, by numerous
coats of gloss Poly that are alternated between sanded and
unsanded high gloss with the sanded coats applied while the
unsanded high gloss is still very slightly tacky, so it will
adhere well over the unsanded high gloss. This method gives
the illusion of depth by leaving reflective layers beneath
the polished layers. It is not as hard a final finish, so
I do not really recommend it, but it will give depth, and
will eventually get quite hard, but it takes a long time.
I really do not know how one would get more "depth"
without endless numbers of sprayed lacquer layers, which is
just an unreasonable amount of intense labor.
|
