_First Steps in Finishing._--The first step in finishing woodwork is
to clean it up and prepare it for the filler. Too great care cannot
be taken in examining all surfaces for slight oversights that have
occurred in the joinery work or for blemishes that have been acquired
in any part of the process of construction. Light planing, chiselling,
or scraping, and perhaps a little sand-papering, always with the grain,
may be needed to remove these faults and blemishes. The most serious
of these generally result from gluing. All surplus glue should be
carefully removed, even to the film that soaks into the surface of the
wood. The slightest spot of glue remaining will keep the filler out of
the wood and show through any kind of finish.
_Importance of Filling._--As soon as the furniture is thoroughly
cleaned, if it is to be finished in the natural color, the grain of the
wood must be filled with a light, transparent, semi-liquid substance,
known as the filler, which, after standing from five to seven minutes,
should be thoroughly rubbed off with a piece of coarse cloth or a
handful of shavings. This process, as its name indicates, fills the
pores of the wood and protects them against the absorption of moisture
and the consequent swelling. But this is by no means its chief purpose.
Strictly speaking, filling is the ground-work of all subsequent
finishing processes and, for that reason, it may be said to be the most
important operation connected with wood finishing. If improperly done,
no amount of good work with the varnish brush will remove the fault. In
fact, good work is impossible after a bad beginning. Good varnishing or
good finishing of any kind requires that, before the final finishing
processes begin, the surface should be made perfectly level and smooth,
free from all unevenness or roughness or minute openings of any kind
that might allow the varnish or other finishing material to penetrate
the wood. If the filling has not been so thorough that no part of the
subsequent finishing material can be absorbed by the wood, a rough
surface will be sure to follow. This may, of course, be rubbed down and
re-finished, but never with that perfection of result which is assured
by laying a good foundation in correct filling. It may be set down as
a fundamental principle of wood finishing that the best result is
obtained when the filling or surfacing has been so thoroughly done that
the thinnest of finishing coats, few in number, are required to produce
the desired result.
_Liquid Fillers or Surfaces._--There are many kinds of fillers in
common use, but they may all be considered as belonging to one or the
other of two classes. They are either liquid fillers or paste fillers.
Woods differ greatly in the coarseness or fineness of their grain. The
coarse or open-grained woods require a filler with body enough to close
up the pores of the wood and give that perfectly even surface necessary
as a foundation for good finishing. The close-grained woods, on the
other hand, do not present the same filling problem. They could not
absorb a paste filler. In fact, it is hardly too much to say that the
fine, close-grained woods, like maple, gum wood, and birch, do not need
a filler at all; and there are some coarse-grained woods, like southern
or hard pine and cypress, the pores of which are naturally filled with
gummy or resinous substances and will not absorb an artificial filler.
But all such woods _do_ need to be given a finishing surface which will
prevent the finishing coats from soaking into the fibre of the wood.
This is the office of the so-called liquid fillers, which are very
properly called "first coaters" or "surfacers."
_How to Make a Liquid Filler._--A standard formula for the preparation
of a liquid filler is as follows: Mix four parts by weight of carbonate
of soda with six parts of china clay, and grind this mixture in about
eight parts of japan, thinning the product with turpentine or benzine
to the consistency of linseed oil. Laundry starch may be used in place
of china clay, giving a filler which is somewhat easier of application
than the clay filler because it does not settle. It lacks in
durability, however, especially if it is not well covered. The finest
grained woods do not require the addition of any material to the filler
to give body. A great variety of liquids may be easily obtained which,
without being mixed with anything, will give the necessary surface.
Glue size, water glass, and the cheaper grades of varnish, thinned if
necessary with benzine or turpentine, are often used for this purpose.
But these are all inferior to the standard surfacers and never should
be used on the best grades of woodwork. Shellac is always preferred
as a first coater for hard pine, as it keeps the resinous sap in the
pores of the wood and preserves the natural colour of the grain. If
oil is applied to hard pine without first applying this protecting
coat of shellac, the wood blackens with age. Shellac is an excellent
first coater for other woods also. It is commonly used in house
finishing as the surfacer for the interior trims. But it dries rapidly,
and generally with a rough surface. The first coating of shellac,
therefore, requires careful sand-papering before the varnish is put on.
_Time Needed for a Shellac Coat to Dry._--It may be well to caution
the amateur finisher as to the time required for the thorough drying
of shellac. While it may be truly said to dry very rapidly, the first
drying is necessarily upon the outer surface, forming a hard coating
which delays somewhat the drying throughout, so that a shellac filling
is not really dry enough to sand-paper a half hour or so after it has
been applied, though it may appear to be. It is a good rule to allow at
least twenty-four hours for thorough drying; and it may be well to add
that all methods of filling, rubbing off, etc., require for the best
results more time than energetic workers sometimes allow.
_Cost of Surfacing._--A practical question that the amateur finisher
will ask is, how can one know in advance how much filler is needed for
given pieces of work, and what will be its cost? For a good quality
of liquid filler it is safe to say that one pint will cover eight
square yards with one coat. The cost varies greatly, depending upon
the quality of the filler and whether it is home-made or obtained of a
dealer. A good commercial filler or surfacer can be bought for $1.50
per gallon, making the cost per square yard of one-coat surfacing about
2-1/2 cents. A small can costs 15 cents. Good work cannot be done with
the cheaper grades of filler. Shellac, which is, all in all, the best
of surfacers, can be bought for $1.85 a gallon, which would make the
cost of surfacing somewhat under 3 cents a square yard.
_How to Make a Paste Filler._--A good paste filler, such as is required
for the open-grained woods like oak, ash, baywood, and poplar or
white wood, may be made from pulverized and floated silica as a base,
thoroughly mixed with raw linseed oil, turpentine, and japan in equal
parts, with enough silica added to the liquid mixture to form a good
paste of a consistency somewhat thicker than paper-hangers' paste.
If the mixture should prove to be a little too thick, it may easily
be thinned with turpentine. The final mixing of this filler requires
grinding in a hand mill. Unless a considerable quantity of it is needed
it is quite as well to purchase a can of the paste filler of a dealer
in painters' or finishers' supplies, though commercial fillers are
not generally quite so good as a one made on this formula. They often
contain wax and whiting and other materials as a base which are not so
satisfactory in the long run as the floated silica.
_How a Paste Filler is Applied._--Paste fillers should be spread on the
surface to be filled very liberally with a wide, stiff brush, allowed
to stand from five to seven minutes, and then rubbed off with a piece
of burlap or a handful of fine shavings or excelsior. But it must not
all be rubbed off or drawn out of the grain. This is an easy mistake
for an inexperienced worker to make. The thing to do is to rub it in
and at the same time leave the surfaces smooth. The surfaces should
then be allowed to dry for about twenty-four hours before receiving the
final finishing coats.