The importance of a good foundation surface--even, smooth, and free
from unsealed pores that would absorb and thus undermine the first coat
of varnish--has been explained in the section on filling and surfacing.
If this foundation has been well laid, the amateur finisher may enter
upon the varnishing stage of his work with confidence; but he will
soon learn that there is much call for skill in order to produce the
desired results in this part of the finishing process. The selection,
preparation, and application of varnish is a special calling, and great
skill comes only as the result of experience; but certain main facts
and principles are easily learned.
_How a Good Varnish is Recognized._--It is hardly necessary to say
that a superior varnish must be clear, transparent, and brilliant.
These qualities are always associated with this kind of finish. But
durability is also a necessary quality. An expert will, with his eyes
shut, recognize a high-grade varnish by its peculiar odour, which is
to him an agreeable one. He will at once detect inferior grades by the
rank, sharp odour of resin and benzine used in their manufacture. The
range of quality and cost in varnishes is probably greater and more
varied than in any other finishing material. For fine, artistic work
only the best varnish is allowable; and this may be bought for $3.00 a
gallon.
_"Sag" and How Corrected._--A good varnish flows easily from the brush,
spreads evenly, and dries slowly, thus allowing plenty of time for its
proper distribution over the surface. And time enough should be taken
to apply an even coat which will not dry unequally and lead to cracking
due to irregular contraction in the process of hardening. It is of
the utmost importance that each coat be spread evenly over the surface
when first applied. Great care should be taken not to brush long in
one place. Re-brushing after a brief interval leaves brush marks which
are objectionable. Unequal spreading on broad surfaces often causes
the varnish to run or "sag." A tendency to sag may be brushed out if
attended to promptly. But, if it is not noticed until the varnish has
begun to set, the only way to prevent a bad blemish is to absorb the
thickening parts of the coat by means of a partly dried brush; and this
must not be attempted three or four minutes after the varnish has been
put on. By that time it will have become quite well set and a sag will
be beyond repairing by any simple means.
_Time Required Between Varnish Coats._--The best varnishes, as has
been stated, dry quite slowly, and they seem to dry and harden not, as
shellac does, on the top first, but from the under surface outward.
This peculiarity emphasizes the need of allowing sufficient time
between coats. And it should be added that mere drying is not all
that is required. Each coat must harden; and during the process of
hardening slight movements take place throughout the mass of the coat
until it becomes permanently set or hardened. The time required for
this permanent setting or seasoning, as it may be called, varies with
the character of the under coat, with the temperature of the room in
which the finishing is done, and with the thickness of the varnish coat
itself. Five days is usually thought to be a short seasoning period.
As many weeks would not be too long for the best results. It is folly
to attempt to hurry up a job of varnishing. In the nature of the case
it cannot be hurried without yielding disastrous results. There is no
other kind of work in which "haste makes waste" with the certainty that
it does in varnishing. Great pains must be taken with each coat. Least
of all should the under coats be slighted, for solidity and depth in
the appearance of the finished surfaces depend upon there being plenty
of evenly laid and well hardened varnish before the final or finish
coat is applied. All this work should be done in a well-lighted room,
free from dust, and with a good supply of fresh air, kept at an even
temperature, of about 70 degrees--certainly not colder than this, since
a lower temperature prevents varnish from spreading evenly.
_Number of Coats Needed._--The number of coats of varnish required vary
with the character of the work. What is known as piano finish requires
from three to seven under coats of good elastic rubbing varnish, each
well hardened and rubbed down to give under surfaces more even than the
best brushing can give. In addition to these under coats a final finish
coat is needed to give brilliancy and lustre.
_How to Rub Down Varnish._--Rubbing down varnish is a unique and
important part in the process of finishing. The beginning of the
operation consists of long and persistent rubbing with pulverized
pumice stone mixed with oil or with water, if the work is such that
water would have no chance to soak into the pores of the wood.
Whichever liquid is used, a rubbing pad will be found necessary.
This is a block about 4 inches square, made of thick, loose cloth
like felt or hair cloth. In use it is first moistened in the oil or
water and then dipped into a box containing a quantity of powdered
pumice. With this the varnished surface is rubbed vigorously, giving
a circular movement to the pad in rubbing down the broad surfaces. As
the smoothing progresses, less and less of the pumice powder is used.
Near the end of the process enough will be found on the surface or
adhering to the rubbing pad. What remains on the surface is finally
all wiped off carefully with chamois skin, when it will be found that
the surface has been levelled down but that it is covered with fine
scratches due to the grains of the pumice. These are removed by a
second rubbing in rotten stone and oil or water.
_Dull Finish and Flat Varnish._--For many purposes good finishing
requires but one under coat rubbed down and covered with a finish
coat; and this finish coat is often not allowed to retain its natural
lustre. For furniture a dull finish is much to be preferred. It is more
durable, it harmonizes better with its surroundings, and it is more
in keeping with the idea of simplicity and usefulness. In working for
a dull finish it is not so essential to secure depth and evenness of
surface as it is when a high lustre is required, and therefore fewer
coats are necessary. In fact, a dull finish may be given to furniture
without any varnish at all. Two or three coats of shellac, each well
rubbed down, give a very satisfactory result. Wax finish, to be
described later, gives beautiful effects. There are varnishes known as
flat varnishes which give a dull finish without rubbing. They are made
by dissolving beeswax in turpentine in the proportion of two ounces of
the solid to a pint of the liquid, using moderate heat and mixing the
wax solution while warm with four times the quantity of warm varnish.
What is known as the old Dutch finish is obtained by using over the
proper stain one coat of wax varnish. But there is no kind of dull
finish so durable as that given by several coats of high-grade varnish,
each well rubbed down.