Chapter
Ten
Sanding,
Scraping and Finishing
Finishing can be very involved. I spend about 2-3 hours fini=
sh
sanding and scraping a harp.
Some builders will spend considerably more, a few spend less time.
80 Grit Sandpaper with Random Orbit=
al Sander
- I only hit the areas with obvious glue sppots and significant roughness.
120,
160 Grit Sandpaper on a random orbital Sander – I sa=
nd
most of the harp with these two finer grits, carefully inspecting for scrat=
ch
marks left from the last paper. I
usually wipe the hard wood areas with a wet rag to raise the grain and iden=
tify
any glue spots or glue haze before sanding it with the 160 grit paper once
again.
Scraping
– I carefully burnish a fine edge on the scraper and scrape down all =
of
the surfaces, working to remove any last burn or machine marks on the
harp. Again, I use my fingers=
more
than my eyes to inspect the harp at this point, working to ensure all the
surfaces are uniformly smooth.
Finishes
For 10 years I
built furniture and boats. I
liked Bartley’s gel finishes, Deft Brushable Lacquer or Behlen’s
Master Finish ®. They can=
work
well if you have experience with them.&nbs=
p;
The purists really frown on polyurethane, but I think it may be suit=
able
if you expect the harp is going to have to live in a rough environment.
What you do w=
ill
depend on one’s personal preferences and how these fit with the clien=
ts
desires. Some folks like a highly polished, =
glassy
finish. This will require fil=
ling
the grain on many woods. I like
the instrument to look like it was made from wood, and don’t usually =
fill
the grain. Many of the harp w=
oods
(hard maple, cherry) do not take stains as readily as oak or Mahogany, and =
I am
really quite reluctant to stain a harp for my clients.
The largest
problem I had with all of these finishes had to do with their drying time a=
nd reparability. Most of them take several ho=
urs to
dry, and even with a separate finishing room, I had to spend a lot of time
sanding out dust motes that had settled into the finish.
I can recomme=
nd
two different finishing systems depending on the work area and tools the ha=
rp
builder has available. Paddin=
g on
six to eight coats of the alcohol based shellac is the the simplest in term=
s of
tools and material needed. I =
will
describe that first. Sp=
ray lacquer
requires more equipment and a dedicated finishing area.
Padding
6-8 coats of an Alcohol based Shellac
I started usi=
ng
this system after hearing Howard Bryan (A pedal harp restoration expert wor=
king
out of
![](3D"10Book_files/image002.jpg")
Finishing kit: Counter clockwise from the top.
The Alcohol based varnishes are rea=
lly
easy to repair. I used =
to
wonder why instrument builders and furniture refinishers dwelt so much on t=
he
reparability of a finish.
Reparability is not just valuable f=
or
restoring a harp that has been damaged in some way. Every finisher is going to m=
iss
one or two glue spots, lay on a finish too thick and have it run or sag.
There is one drawback to traditional
spirit based varnishes. Shell=
ac is
a primary component, and shellac has a limited shelf life. I order from a supplier that=
is
turning over their inventory at a good rate and store it in my basement shop
which stays cool throughout the year. I know it lasts at least 10 =
months
under these conditions. If
the varnish is old, or has been subject to heat, I would recommend trying i=
t on
a sample to make sure it will cure. &=
nbsp;
Old shellac will not cure into a hard coat, and will remains
sticky. Make sure it wi=
ll
cure hard before applying it to the harp.
After reading a few books on rubbed
varnishes, I was thoroughly intimidated by the French pad technique. If you can find =
an
expert willing to tutor you on the intricacies of the traditional technique=
and
method, great. They work best=
on
flat horizontal surfaces, and my harps have a lot of surface that isn’t flat or
horizontal. I adopted a
simplified technique largely based on Howard Bryan’s advice to the ha=
rp
list.
Description of
the Simplified French Pad technique
-Tools and Materials
The varnish is applied to the harp =
with
mushroom shaped pad that is made from an old, clean cotton T-shirt. The outer layer is an
8”x 8” square of cloth held in place with a rubber band or zip
tie. When the pad is compacte=
d and
formed, it should be about 2 ½ “in diameter and ¾”
thick.
I mix equal parts of varnish and Be=
hkol®
solvent in a half pint “squirt bottle”. My bottle was originally used for
dispensing saline solution for contact lenses. I drilled the hole in the ca=
p to
1/16”
I use a Q-tip to apply finish into
nooks and crannies, and I store two pads and Q-tips in an a discarded Sour
cream container (with a tightly sealed cap) between uses. The layer of cloth on =
the
outside of the pad will wear through after applying three or four coats of
finish, and I replace it with a new square of cotton. The tools to apply the Violin
Varnish cost pennies at most.
The Varnish is $19 per pint (in 2005), and the Behkol runs another $=
9,
but that is enough to finish three or four harps.
-Method
Finish is applied to the pad then t=
he
pad is used to apply the finish on to the harp. It takes a couple of tablesp=
oons
of finish to saturate the pad the first time you use it. The first three of four strokes ar=
e made
in a circular motion to distribute the finish evenly over the area. I use the pad to move finish=
from
areas that are puddling, sagging or running to areas that are dry. Within 8-15 seconds most of the al=
cohol
has evaporated and the finish will become tacky. The final strokes should be =
made
before it begins to tack up and are linear, along the grain.
Because the finish dries rapidly, I
usually limit the area I am finishing to a square foot. When I am ready to =
move
on to a new area, I renew the pad with a squirt of fresh finish.
It takes me about 25 minutes to app=
ly
one coat of finish to a five octave harp. At that point, the fir=
st
area varnished will be dry to the touch, and I will put on a second coat.
It takes four or five hours for the
varnish to cure hard enough for sanding. I take care of any flaws, th=
en
sand the entire harp with 220 grit paper.&=
nbsp;
The object of this sanding is to remove any surface roughness –=
; no
more than the top 30% of the finish.
Do not sand the finish off to bare wood.
I brush the sanding dust away with a
shop brush and tack cloth and apply two more coats and let them cure for
another 4 hours (or overnight) before sanding the parts with 320 grit
paper.
At this point I am getting a pretty
good build on the finish.
I will apply 1-3 more coats, “sanding” in between coats =
with
copy paper. This paper =
seems
to cut about as well as 500 grit sandpaper. As you rub the finish, the paper w=
ill
take on a sheen, at which point you will need to change to a new fresh sect=
or
of the paper so it will continue to abrade and smooth the finish. Copy paper loads up a bit qu=
icker
than real sand paper but is much cheaper.
I pay special attention to the stri=
ng
rib and the side of the neck that will be under the strings. If I get the finish I want in these
areas, I can proceed with mounting hardware and stringing. I can return at my leisure to touc=
h up
any areas after I have strung the harp.&nb=
sp;
It takes about two weeks for the harp to start holding its tension
before mounting levers, so I have ample time to inspect the harp and identi=
fy
and correct any blemishes.
After the finish has cured two days=
, I rub
out the entire instrument using Behlen’s Deluxing Compound. It is a lot like the rubbing
compound used for car finishes. It removes any dust motes, and
gives the finish uniform semi-gloss sheen, leaves a light coating of wax on=
the
surface of the instrument.
Target
Coating’s Water Based Ultima Spray Lacquer (USL)
After Asking
Larry Fisher to explain how he got his incredible finishes, I found that ma=
ny
Luthiers have been adopting the Target Finishing System. It is a water based finish, but rep=
licates
many of the best qualities of a nitrocellulose lacquer. Spraying requires a larger investme=
nt and
more set up time than shellacking but once I had invested in an HVLP spray =
rig,
a proper respirator and set up a ventilated clean finishing area, I found t=
hat
I could get a smoother, deeper gloss with less effort. Here is the process that I
use. You will be able to find=
several
other variants (that involve more steps and work) on the Internet. They may result in a glossier, thic=
ker finish,
but I think this is one of the best for the effort invested.
1. First I la=
y on
two coats of the Alcohol-based shellac.&nb=
sp;
It may be tempting to =
skip
this step and start with the Target Coating’s USL, but I find the res=
ult
has that grayish-blue tinge that many water-based finishes suffer from.
2. I screw an=
eye
hook in the top of the sound box and use twine to hang the sound box and th=
e Neck/pillar
from overhead hooks while spraying. I find it works best to hang the pi=
llar
from a bolt in the foot and spray it upside down. To spray the top of the neck (now f=
acing
the floor), simply grab the dowels extending from the knee block to swing t=
he
neck into a vertical position.
3. I spray on=
four
coats of USL, with each coat spaced at least an hour apart.
4. After the =
paint
has cured for three days, I sand and level it with 400 grit paper. A fully cured finish takes about 8=
days
(depending on the temperature and humidity in your shop). Several instrument finishers have f=
ound
tha the enters this nicely sandable state at about three days. Before that, it tends to gum up th=
e sand
paper. After four days, the f=
inish gets
much harder to sand. Thorough=
ly
wipe off any excess sanding dust.
5. I spray on=
four
more coats of USL, with each coat spaced at least an hour apart.
Now, at this point many of the viol=
in
and guitar finishers go through two or three more sanding (800 grit) and sp=
ray
painting cycles. I think that=
may
be overkill, and will usually let it the finish cure the full 8 days, then =
rub out
the finish with Behlen’s Deluxing Compound.
Copyright ©
2007, Rick Kemper