LINSEED OIL
Manufacture
Linseed oil is expressed from common cultivated flax-
seed (Linum usitatissimum) . This is grown in all parts
of the civilized world. It grows from almost the sub-
arctic regions down to tropical countries, and even in
these in elevated regions.
The process of extracting the oil from the seed is a
very simple one, and once every little town or hamlet
had its crushing mill and extracting presses. To-day in
this business as well as in that of every other commercial
commodity, the manufacture of linseed oil is in the hands
of large concerns, and the small plants have gone out of
the business.
The flaxseed is ground into meal, and this is either cold
pressed or heated, and the oil pressed out of it by powerful
hydraulic presses. The oil flows out, and the solid parts of
the seed remain in what is well known as linseed-oil cake.
The cold-pressed oil is clearest, palest, and best; but as
by that process it cannot be made to yield nearly so much
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oil as when the flaxseed meal, has been heated, that is
very seldom practiced now. This is a pity, for cold-
pressed linseed oil is superior for painting purposes, and
is clearer, more fluid, and free from much deleterious
matter which is extracted by the hot system.
There is still another system in use for extracting the
oil from flaxseed, and a still greater percentage of oil is
obtained from it than by the use of either the cold or
hot system of pressing. This is known as the percolation
process.
After the grinding of the flaxseed into meal, this is
placed into a percolating tower running through the
several stories of the factory building. When filled with
flaxseed meal, this is saturated with benzine or naphtha,
and more of that subtle fluid is poured upon the meal at
the top of the tower. This is continued until all traces
of oil have been dissolved and removed from the meal.
The naphtha charged with the dissolved linseed oil runs
downward to the bottom of the tower into a pipe, which
conducts it to an apparatus where it is heated. The
naphtha, being a very volatile oil, is evaporated at a com-
paratively low heat. These vapors are conducted to
condensers, and the vapors soon condense into what they
were originally naphtha. This is used over and over
again; there is but very little loss of it. The remaining
oil is entirely freed from the naphtha by this heating, if it
is properly managed. It is claimed by some that by
this system, certain substances are dissolved which
would remain undisturbed by pressure, and that the loss
injures the durability of the linseed oil for outdoor work.
This claim, however, may not be well founded, and may
be due to prejudice or the self-interest of concerns that
press oil. Some again claim that it is better. However,
so many from all parts of the country claim differently,
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that one should be slow in making the change from one
to the other. Experiment with them side by side under
varied conditions. This system has some good points in
it. Naphtha does not dissolve moisture, and linseed oil
thus made is as nearly free from it as it is possible
for it to be, and this cannot be said of the heat-
expressed oils. The real difference between the pressed
oil obtained by heat and the percolated oil, cannot
be so great as to deter any one from using either, but
the chances are that the old-fashioned cold-pressed oil is
the best.
Linseed oil made by whatever system, may vary a
good deal in its quality from other causes than those
pertaining to the system of extraction. It varies greatly
accordingly as it is made from good or from bad flax-
seed. That made from East Indies, imported flaxseed
(better known as Calcutta seed, from the city from which
it comes) is usually better than that obtained from Ameri-
can seed. Its product, sold as Calcutta-seed oil, is usually
freer from moisture than that which is made from flax-
seed of American or Russian origin. Varnish men who
ought to be good judges of quality in linseed oil, prefer
it to all others, in the preparation of varnishes, as they
must have a dry oil, containing but little moisture.
American flaxseed, when properly harvested, is as good
as any in the world but there is the trouble, it is not
harvested properly. In America, flaxseed is harvested by
machinery, the same as wheat. Owing to the ease with
which it shells out when the sickle strikes the plant, the
cutting cannot be delayed until the seed is ripe, as it
would all shell out and fall to the ground; so the crop is
cut down before it is ripe, just as the seed begins to change
from the dough state and begins to harden. In that
ccndition, it is saved without shelling but it is far from
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being fully ripe. In the East Indies, where labor is very
cheap, it is pulled by hand, when the proper times comes,
and thus they are able to secure it in the very best con-
dition. This is impossible in America, hence American
seed does not equal it.
So with poor seed to start with, and a larger quantity
of oil expressed out of it than in the good old days of
cold presses, there can be no wonder at the complaints
that linseed oil does not wear as well to-day as it did in
old times.
For good work, it would pay to use cold-pressed oil,
even at an expense of several cents more per gallon. It
would pay architects to specify it in their contracts, and
property owners should be willing to foot the slight
increase it would make in their painting bill, if they
could only be made sure that they were getting it after
specifying it and paying for it. But quien sdbe?
Linseed oil, after it has been pressed, should be tanked
for three or four months to allow it to deposit some of
the foreign matter pressed out of the seed with the oil,
and with which it is more or less charged. This will
settle to the bottom of the tanks, and is called linseed-oil
foots. It will do so naturally, if only time enough be given
but it is not allowed.
Manufacturers being human (in some ways) do not take
kindly to the idea of having vast sums of money tied up
for several months in a tank. They want to turn that
money over and over before the oil would be fit to sell in
the natural way it has of doing this work, so they arti-
ficially hasten this precipitation.
There are two ways of doing this; one is known as the
alkaline process. As this is the poorer of the two, no
time will be wasted upon it. The other is by trituration
with sulphuric acid.
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Sulphuric acid does not affect linseed oil injuriously, and
it acts only upon the impurities which precipitate rapidly.
The oil is then well washed with water by trituration
until it is free from traces of acid, and is then considered
fit for use. Varnish manufacturers who are most careful
in the purchase of linseed oil usually still further refine the
oil by repeated agitation of it with sulphuric acid; and the
grinders of fine pigments requiring refined oil, use it also
for the same purpose. With both of these sets of men,
clearness and limpidity are of the first importance; but
painters of the old school who can remember the time
when they went to the town mill and bought cold-pressed
oil settled in the old-fashioned way, and used it to mix
their pigments with, claim that three coats of such oil
and white lead would wear for years before it would com-
mence to chalk. Now a like number of coats prepared in
the old way, but with oil such as it now is, will appear as
so much whitewash in the same number of years. It
will require something else besides plausible talk to make
them believe that the oil they buy to-day is half as good
as the old-fashioned, cold-pressed, naturally settled oil
made from pulled flax which it was possible for them to
buy some seventy years ago.
Chemistry of Linseed Oil
Linseed oil is a complex product, and its drying or
solidifying is due to its becoming oxidized. Condit says:
"To understand the action that occurs when oil dries,
we must know the composition of it. Linseed oil is
composed of linolein, palmittin, and olein. To non-
chemists, these words are mere names; but let us designate
linolein by A, palmittin by B, and olein by C; now A the
first is composed of linoleic acid and glycerine ether,
B of palmitic acid and glycerine ether, and C of oleic acid
196 MODERN PIGMENTS
and glycerine ether. Glycerine ether is the base to
which the other constituents are attached. Looking upon
glycerine as D, we may represent the other constituents
as allotted in this manner:
A
B
=D
Chemically considered, these salts (A, B, and C) are sus-
ceptible of parting with their base glycerine (D) in favor
of some base possessing a stronger affinity for oily acids."
The Drying of Linseed Oil
"This kind of decomposition in point of fact really
takes place under proper conditions, and the resulting
soap varies in its nature according to the base employed.
Take an instance: Suppose you have rubbed some linseed
oil on a sheet of glass or china (I mention these substances
to preclude the idea of the absorbance of any part of the
oil which would take place if wood, etc., were used) and
it has sufficiently dried not to become sticky, and that
when in that condition you wash it with a solution of soda
in water, the soda dissolves the glycerine to unite with
the oily acids (linoleic, palmitic, and oleic) and forms a
soap, leaving the glycerine free. In other words, using
the above formula: A, B, and C unite with the soda (or
other alkali) and leave D a free agent. Now this D is
soluble in water, consequently the soap which is formed
(by the union of A, B, and C with the alkali) is also dis-
solved. This soap, by the way, is not like the ordinary
hand soap, but is a frothy matter that gathers on the
glass. Hence, by washing the oil with sufficient soda and
water, every trace of oil is carried away from the glass."
The above explains what would take place if the oil
were left in an undried state, and to some extent what does
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take place when linseed oil is washed over with alkalies
even when dry. It is the same action which takes place
when the alkaline removers take off paint; but to return
and find out how oil dries, Condit further says:
" In speaking of the drying of linseed oil merely a
change from the liquid to the solid state is meant. Now
the constituents of the four components of linseed oil
consist of oxygen, hydrogen, and carbon in varying pro-
portions; that is, linoleiu A, palmittin B, and olein C are all
made up of the above elements, differing in proportion
just as the letters A, B, and C are made up of straight lines
and curves, differing, however, from each other in the
totality.
"Now in the change from the fluid to the solid con-
dition, i.e., the drying process, oils suffer a slight loss of
carbon and oxygen, but they gain about one tenth of
their own weight in oxygen. It is by this union of oxygen
with the component of linseed oil that they dry or harden.
Put them out of the influence of this element and they
remain fluid. Slow-drying oils lose least in weight; they
contain more of the non-drying fats, and for that reason
seem to gain more in weight (in time)."
The process of drying, while it is very simple, in theory
at least, is most intricate, and would require too many
explanations to follow it up in all its details, so it
cannot be given here as fully as some might wish. To
properly handle the subject would require a large
volume, therefore a resume is given below in short
paragraphs, which contains the gist of the process; it, too,
is from Condit :
" 1. Linseed oil is composed of linolein drying oil, 80
parts; palmittin and olein non-drying oils, 20 parts, of
which 8 parts are glycerine ether which flies away in the
process of drying.
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"2. Pure oil will not dry in darkness; and the greater
the light, the more vigorous the drying.
"3. Heat is also a powerful drier of oil; oils heated
for a short time continue to dry more rapidly for a long
time after the heating.
"4. Drying appears to be the loss of glycerine ether
and the gain of oxygen from the air, the glycerine appear-
ing to be loosened from the oil acid as the oxygen unites
with the oil, the result of the drying being a light varnish.
"5. Some of the non-drying oil acid also flies away in
the drying, especially under the influence of direct sun-
light or when the oil is heated; 100 parts of oil become
111 parts (more or less) heated; it loses 3 parts (more
or less); net gain 8 parts.
"6. Most of the glycerine ether which is linked with
the oil flies away in the drying.
"7. When oxygen combines with a drying oil that
is, a fixed oil caoutchou or gluten is produced, which
in reality is the hard, horny, elastic body that renders it
'dry.' It is the ' skin' that forms on top of a pot of paint
when it has been left undisturbed for some time.
"8. The drying of oils appears to depend upon the
presence of oxygen, which, by an incipient combustion
of hydrogenous oils, fixes them. Whatever contributes
oxygen is a drier, as is the case with pure air, sunshine,
etc. So also the perfect oxides of metals, including even
pure earths and alkalies in due proportion, dry oils; the
best are those which contain oxygen in excess, such as
litharge, sugar of lead, minium or red lead, the oxides of
manganese, sulphate of zinc, white copperas and verdigris."
Properties and Uses
Raw linseed oil is penetrating and elastic, and after its
oxidation or drying it remains as a waterproof rubber-
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like substance, holding firmly whatever pigment it has
been mixed with. Some pigments act chemically upon
it, as, for instance, the lead salts, which have the property
of turning it into a soap, which, however, is not a readily
soluble one (after drying at least); the lead oxides are
noted for this property, as red lead and litharge. Not-
withstanding that a great deal has been said as to the
beneficial influence exerted by the totally inert pigments
which in a measure is true it is equally true that
some very active ones, combining chemically with lin-
seed oil, exert a very good influence over it, as occurs when
red lead and linseed oil are combined, the resulting
linoleate soap being, when dry, insoluble in water. It
is not acted upon injuriously by that element, which is
most destructive to linseed oil ordinarily. This, how-
ever, is not true of all active pigments, some of them
exerting baneful influences upon linseed oil as they com-
bine with it to form soluble soaps. Pigments containing
lime in a caustic form are of that character.
The inert pigments naturally do not exert any influ-
ence upon it one way or another, and when linseed oil
has been mixed with them no chemical action takes
place; the drying and longevity of the oil remain the
same, generally speaking, as if the pigments had not
been added.
The above statement was purposely qualified by saying
generally speaking, because in one way they do exert an
influence which, while it is not chemical, is a mechanical
one, in this way: Some pigments are very heavy and have
no affinity for oil, and naturally take up but little when
mixing them into a paint; others again are very light
and take up large quantities. It is reasonable to suppose
then that the pigment which has not taken up much oil
will be a drag upon the oil, as a little of it is scattered over
200 MODERN PIGMENTS
a great quantity of pigment atoms, so that but an infin-
itesimal portion has to perform a duty that is above
its strength, and so it is. Such pigments cannot be
depended upon for outdoor work.
On the other hand, the pigment which holds up large
quantities of oil mechanically prolongs its life.
Again, there is a class of pigments containing non-
drying elements in their composition, which prevent the
oil from drying, such, for instance, as uncalcined lamp
black, vandyke brown, etc. These cannot be safely used
without first preparing the oil, so -that it shall contain
sufficient drying energy to overcome their deficiencies.
Artificial driers must be added to the oil to hasten its
drying. Otherwise, these pigments exert a good influ-
ence upon the longevity of the oil, as they take up so
much of it.
Linseed oil continues to absorb oxygen after, seem-
ingly, it is as dry as it is possible for it to be, or long after
it has ceased to feel tacky to the touch. The fact is that
when it has reached that stage where no further oxida-
tion takes place then its downward grade of decay may
be said to have commenced.
Linseed oil, while it may not be as good as it was fifty
years ago, when it was all cold pressed, is usually found
pure, such as it is. It is, of course, possible for some of
the dealers to practice the adulteration of it, but it is
seldom that that occurs. Jobbers, in the past (a few of
them), who did not care for reputation, did mix oils, but
now such a thing is next to impossible. What with
nearly every state having special laws, which no one
would take any risk of infringing, and behind these Uncle
Sam with his own strict laws to prevent fraud the
practice of adulterating linseed oil has about become
obsolete.
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Linseed oils are, however, imitated; but the imitations
are sold as such. There can be no harm come of it, for
no one is cheated. If a painter is foolish enough to
believe all the stuff that smooth-tongued strangers tell
him regarding the merits of nonpareil, indestructible
enamelling liquid, in the way of throwing linseed oil in
the shade, and supplanting it everywhere, he has a perfect
right to believe and to give his money away for it. The
law recognizes him as a free agent and will not forcibly
keep him from flinging cash in the river, if he so wills.
It takes money to buy experience, and with some men
it only seems to last until the next deceiver comes around
with another bait 10 cents a gallon below the market
on linseed oil!
Barnum said: "For every fool that dies, two are born."
It must be true, or the concerns manufacturing dope oil
could not flourish as they do.
Impurities, and Tests for Them
It is a very hard matter to determine impurities in
linseed oil, and nothing short of an analysis made by an
expert chemist used to that sort of work will be of any
value. This work is intricate and expensive. But
anyone can readily determine to his own satisfaction
whether linseed oil is adulterated or not. At least,
raw linseed oil can be so tested, but not the boiled.
There is no test that one can make for himself that will
do .for that.
There are several tests. One, the most usual, is the
nitric acid test. Although it is a simple one to make, it
is apt to lead many into error, if they are unused to
testing oils. To make the test: Take a bottle, or any
other glass vessel, pour into it about equal parts of raw
oil and nitric acid one ounce of each is enough for the
202 MODERN PIGMENTS
purpose. Shake the bottle, so as to mix the oil and acid
well together, and put it away to rest for a quarter of an
hour. If the oil is pure, the nitric acid will settle at the
bottom of the bottle, where it forms a distinct layer
below the oil which floats on top. The nitric acid in a
well-made oil will be found clear, but tinged to a light
straw, from coloring matter extracted from the oil during
the shaking; the oil itself in the upper layer will be- found
to have turned to a brownish color, but of a clear tone.
If adulterated, the oil will be from dark brown to black
and muddy, lumpy or "livered," according to the nature
of the adulterant. The acid will be brownish, and often
its limpidity even will be impaired; but not always so,
this depending also upon the nature of the adulterating
oils. It is impossible thus to determine the adulterant
that requires a chemical analysis.
Then there is the specific gravity test, which is always
satisfactory, as it is a very hard matter to adulterate oils
so that this will not be greatly changed. It requires
apparatus to make this test, but that is not very expen-
sive: a suitable hydrometer, one that is adapted to oils
or fats, with a thermometer, are all that will be needed.
The oil should be poured into a vessel, which must be
considerably deeper and wider than the hydrometer,
which is dropped into it, and which must float clear of
the sides and the bottom of the oil receptacle. The
specific gravity of linseed oil is, say, 0.932 at 60 F. Now
if the hydrometer is placed in the oil and the top of the
bulb indicates .928 or .934, if the temperature of the oil is
either above or below 60 F., a correction must be made
for that, as the oil will show a lighter gravity if below the
standard temperature and heavier if above. Deduct or
add .00035 for each degree of variation in temperature
either above or below the standard, and, if the oil is pure,
VEHICLES 203
the total ought to be 0.932. If it varies very much, the
oil is adulterated.
Then there is the flash test, but this is rather com-
plicated and requires more apparatus to determine cor-
rectly. The two above-mentioned tests will be sufficient.
Besides, the nose and the eye can be made nearly as
efficient as any, at least for certain kinds of adulterants.
Linseed oil has a smell all its own, and neutral oils can be
readily detected by their odor with the nose, they have
also a bluish fluorescent tone that the eye can readily
note, so that, with the help of these organs, a double test
can be made, and one or the other will be apt to uncover
the adulteration. The nose will also detect animal or
fish oils, which may be used in adulterating; however, the
chances are that it will be hard to find any as long as they
stay above the cost of linseed oil.
BOILED OIL
As it has already been stated the heating of linseed
oil renders it more drying. When it is boiled at a great
heat along with some of the oxides of lead or manganese
it is rendered thereby still more drying.
For mixing with some of the non-drying pigments,
its use is imperatively demanded, at least for the
grinding of them into pastes. Boiled oil is less
elastic than raw oil, and, being darker, it tinges
the white pigments and some of the light tints to
an undesirable degree. It is also much less elastic
than raw oil and less penetrating, therefore it should
never be used for priming purposes. It partakes of the
nature of a varnish, and dries upon the surface with but
little penetration.
It is therefore better adapted for interior painting than
it is for that of outside work. Its use is indicated, how-
204 MODERN PIGMENTS
ever, for many purposes where penetration and elasticity
are not of prime importance.
Adulteration
Under the heading of raw oil, it was said that all tests
which were indicated for that were useless when applied
to boiled oil, and so they are. It requires an expensive
chemical analysis. Unless, of course, that the adulterat-
ing has been so carelessly done that the nose and eye can
be utilized to ferret it out, as is the case when neutral
oils have been added.
The most frequent adulteration, if adulteration it be,
is in many dealers taking, say, one barrel of raw linseed
oil pouring the contents of it into the boiled oil tank and
adding from five to ten gallons of some cheap benzine
manganese dryer. Boiled oil thus prepared is called
bung hole boiled oil. It is simply raw oil with probably
a bigger dose of liquid drier than would have been the
case if the painter had added it himself.
POPPY SEED OIL
Properties and Uses
As the name implies, this excellent paint oil is produced
from the seed of the poppy plant opium poppy, or
papaver somniferum. It is nearly colorless and very
clear, so these qualities render it of great value for the
mixing of white pigments or for that of tender
light tints. For China finish or interior enameling,
for instance, it is invaluable. In this connection
it should be used with zinc white in preference to
linseed oil, which has the property of darkening the
more quickly that it is shut away from the sun's
rays. This defect does not belong to poppy seed oil.
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Zinc white of good quality is ground in it to a paste
form, and so labeled when offered for sale.
Poppy seed oil is a slow drier, so it requires a longer
time for paint mixed with it to become dry. Its binding
properties are no better than are those of linseed oil
if as good. Its high cost compared to that of linseed oil
will always prevent its use. It is, therefore, but for
expensive enameling that its use is ever resorted to by
the general painter and decorator. Artists, of course, can