Improvements in the Method of Finishing or Polishing the Surface of Wood or other like Material.
Year: 1893

page_text: Date of Application, 24th Oct., 1893-Accepted, 23rd Dec., 1893
Improvements in the Method of Finishing or Polishing the Surface
of Wood or other like Material.
A communication from abroad by VICTOR VICTORSON, of Temple Street, West
Roxbury, in the Commonwealth of Massachusetts, one of the United States
of America, Inventor.
I, ALFRED GEORGE BROOKES of 55 & 56 Chancery Lane in the County of
London, Chartered Patent Agent do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
In the manufacture of pianos and other articles of wood which require a high
finish, it is customary to apply thereto successive coats of varnish, and the higher
and more durable the finish desired the greater the number of coats must be applied,
usually from four to six coats.
Each coat of usual commercial varnish employed on piano cases is exposed to
the air in order that the solvent for the varnish gum may be evaporated and let
the gum harden, from three to ten days being required between successive coats,
and the last body coat is rubbed down to a sinooth surface and permitted to stand
for several days, when a flow or polishing coat is applied, and before this coat is
hard enough to polish it must stand for a period of from ten to thirty days.
A small proportion of oil is added to usual varnish, as is well known, to impart
a slight degree of toughness and elasticity thereto, as otherwise the varnish would
be too brittle to use and would chip and fly from a very slight blow.
Varnish is peculiarly susceptible to climatic and atmospheric changes, and it is
extremely difficult to apply successive coats as described under substantially the
same conditions, for if this is not done the different layers will not harden uniformly,
the unequal shrinkage of the varnish will cause cracks or checks, and the rubbing
necessary to impart a polish will develop all such imperfections.
The usual process is further objectionable because of the time required, as the
slow drying necessitates a large amount of stock in various stages of treatment,
which involves a large amount of unproductive capital and requires great storage
capacity.
The durability of the finish obtained by the process described is not satisfactory,
as the evaporation of the solvent continues for a long time after the article treated
has left the hands of the finisher, and as the gum and small amount of oil harden
interstices formerly occupied by the solvent will show as fine pores or cells, thus
making it impossible to maintain a fine polish.
In my correspondent's experiments to overcome these objections and cheapen the
cost of finishing wooden surfaces, particularly piano cases, he has discovered a
method for finishing such surfaces in from four to six days, with fewer coats of
varnish, at a much less cost, and with positive advantages in the result to be more
fully described.
The improved method, now to be described, is applicable to carriage, furniture
and other wood-work finishing, and by the term wood-work I include articles made
of wood and its compositions.
In carrying out my correspondent's invention I use a varnish which is rich in
oxidizable oil, that is, which has a high percentage of such an oil to thus materially
increase the durability and toughness of the varnish when subsequently treated;
and preferably I use raw linseed oil to secure the best results, though good work
may be produced with boiled linseed or other oxidizable oil, but this varnish

page_text: must not be confounded with japan, which, though having a considerable per-
centage of oil, contains such a quantity of asphaltum or equivalent substance that
its after treatment must be totally different from that of varnish.
The piano case or other wooden article to be finished, provided or not with usual
filling, is coated with a varnish as specified, and placed in an artificially heated
chamber, the temperature of which is gradually raised to about 100° Fahrenheit
and there maintained for several hours, and towards the end of the heating, which
takes from eight to twenty-four hours, according to circumstances, the temperature
is increased to 120° Fahrenheit, more or less, until the heating is finished, that is
to say, until the varnish is thoroughly dry, and this will occur in varying periods
according to the consistence of the varnish, those varnishes of a heavy body
requiring a longer time than those of light body, but, from eighteen to forty-eight
hours, more or less, usually will suffice.
The subjecting of the article to these different temperatures at the stated times
and in the stated manner is necessary in order to prevent injuries to the woodwork
and to the varnish.
Throughout the heating or baking a free circulation of air is maintained in the
chamber, said air co-operating with the heat in securing the proper and desired
result.
The gradual application of the heat overcomes any tendency of the varnish to
blister, and the heat is never great enough to split or twist the wood or soften the
glue, as in a piano case.
As the volatile solvent of the varnish is rapidly evaporated and carried away by
the current of air the superabundant fluid oil takes its place, and as it is oxidized
it fills and hardeus in all the minute pores or interstices left by the solvent, so that,
with the varnish gum, the oxidized oil forms a hard, even and elastic skin or coat,
thoroughly shrunk upon and intimately connected with the surface of the article,
and continuous thereon.
At the conclusion of the heating, the article is removed from the chamber, and
a second coat of the varnish is applied thereto, which is subjected to the gradual
heating amid a free circulation of air, as before.
As many coats of varnish are thus applied and heated or baked as are desired
or necessary, according to the class of work and the nature of the finish.
By my correspondent's method, however, fewer coats are necessary to obtain a
given finish than is possible by the usual methods of treatment, for the varnish
described and used by me has much more body than the varnish in common use.
It is to be observed that varnish having this increased body could not be dried
and hardened by the ordinary method of procedure because of the excess of oil,
and the treatment berein described is necessary to attain a proper result, the
varnish used and its treatment so co-operating, each with the other, that one is
of practically little value without the other.
It has been found that the heating tends to "kill" or deaden some of the
valuable qualities of commercial boiled linseed oil, making the varnish brittle and
less durable.
The successive coats of varnish are thoroughly incorporated with each other,
and form as a whole an even, homogeneous, transparent and hard elastic coating,
oxidized upon each other, and which will not show any variations or demarcations
between the coats when subsequently rubbed.
When the last. coat has been baked the article is rubbed down in well known
manner to a perfectly smooth surface, and then polished; or a flow coat may be
applied and baked, which coat may be at once polished by rubbing with water or
oil, as desired.
To secure the best results the density and fluidity of the varnish, and its
temperature, should be substantially the same for each coat, and if these pre-
cautions are observed this method may be successfully practiced in any and all
conditions of the weather and atmosphere.
By the use of a varnish rich in oxidizable oil, in the manner described I obtain

page_text: a free flow, and a continuous tough surface free from pits or holes, and which, when
dry and hard, will not cross-crack or check; nor will it sweat after rubbing, but
will constitute a most durable and high finish practically proof against atmospheric
and climatic changes.
In classes of work where a high, durable, and lasting finish is required, I use a
varnish which contains about twenty per cent. of oil, but the proportion of oil will
vary according to the character of the work to be treated and the finish desired.
To apply such a varnish, and treat by the methods now in vogue, the time
necessary to even surface-harden each coat would be so lengthened as to be
prohibitive, while the unoxidized mass of oil underneath would remain soft; and
on the other hand, ordinary varnish treated by my improved method would quickly
dry, but it would cross-crack and check, and the small proportion of oil would
be "killed" by the heat so that the surface would be very brittle and chip off in
flakes.
Japan cannot be treated by my method, for the low degree of heat would not
harden it sufficiently to be used with the most careful handling, and as is well
known, japan cannot be rubbed to a polish because the heat generated by the
friction softens and rubs up the asphaltum or equivalent constituents.
The high degree of heat necessary to bake japan prohibits its use on any
substance or article liable to be split, warped, or twisted by such heat, or which is
glued together.
While I have herein specified 120° Fahrenheit as the degree to which the
temperature is raised in heating the varnish coats, it is to be understood that a few
degrees more or less come within the scope of this invention, for if the proportion
of oil is slightly increased or decreased a few degrees more or less of heat will be
required.
While the best results have been attained with raw or unboiled linseed oil I do
not restrict myself to its use in carrying out my invention, as any oxidizable oil
capable of giving the requisite durability, toughness and elasticity to the varnish
may be employed with good results.
So, also, plain boiled linseed oil may be used, by which term I mean linseed oil
boiled only, without the addition of any driers, as distinguished from commercial
boiled linseed oil, for as is well known the latter has added thereto various
ingredients to increase its oxidizing properties, such as manganese, red lead,
litharge, potash, etcetera.
These substances, however, all tend to affect the life and durability of the oil,
and hence commercial boiled oil is not well adapted to the carrying out of my
invention.
Simple boiling of the oil, as is well known, evaporates the water therein, and
thickens and increases the oxidizable properties thereof, but the oil will not flow
quite so freely as will raw oil.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. The improvement in the art of finishing the surface of wood, which consists
in applying thereto a coat of varnish rich in an oxidizable oil, subjecting it to
a temperature gradually raised in a free circulation of air to substantially
120° Fahrenheit and maintaining it at substantially this temperature for a period
of from eighteen to forty-eight hours, more or less, in accordance with the con-
sistence of the varnish, to thereby evaporate the solvent of the varnish and oxidize
and harden evenly throughout the coat the superabundance of oil in the interstices
thus formed; applying a second coat of the varnish and treating as before;
the successive coats of varnish being separately heated and shrunk one on the
other until the desired texture and surface is obtained, whereby a continuous
bard elastic finish is rapidly produced, substantially as described.
2. The improvement in the art of finishing the surface of wood, which consists

page_text: in applying thereto a coat of varnish rich in oxidizable oil, subjecting such coat
to a temperature gradually raised in the presence of circulating air to substantially
100° Fahrenheit, and maintained thereat for a time, and thereafter gradually raised
to substantially 120° Fahrenheit to thereby evaporate the solvent of the varnish
and oxidize and harden the superabundance of oil in the interstices thus formed;
applying a second coat of the varnish and treating as before; successive coats of
varnish being superposed and separately heated until the desired texture and
surface is obtained, and rubbing and polishing the final or flow coat, whereby a
continuous hard and highly polished durable finish is produced, substantially as
described.
Dated the 23rd day of October 1893.
1
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for Applicant.