off the building by simply passing the hand over it. As
stated, this chalking is very gradual and hardly notice-
able at first. The chalking can be hastened or retarded
somewhat by the improper or proper use made of the
binding vehicle; also by the improper or proper admixture
of other pigments.

White lead is a good drier of linseed oil, and requires
but a very small admixture of artificial driers to hasten
its drying; and out of doors, excepting in cold or wet
weather, none are needed. Driers seem to kill the elasti-
city of linseed oil, and to hasten its decay, so that when
used at all in connection with white lead, it should be
done with very modest doses.

Only raw linseed oil should be used with white lead for
outside painting. The raw oil is much more elastic and



22 MODERN PIGMENTS

penetrating than the boiled, nor will the chalking com-
mence as soon when it has been employed than it would
otherwise.

The greater the quantity of raw linseed oil that can
be incorporated with the lead and make it cover fairly,
the longer the time before chalking will begin. It stands
to reason, therefore, that as a small proportion of volatile
oils should be used in outdoor painting in addition to
raw linseed oil as will accomplish the legitimate end in
using it at all, i.e., of rendering the paint more fluid and
of making it set more quickly. The above applies with
even greater force to the last or finishing coat, where
volatile oils should be dispensed with entirely wherever
possible to do so. It is somewhat harder work to
properly spread paint so mixed, that is admitted,
but it can be done. White lead seldom chalks upon
inside work that is not exposed to the weather, and what
has just been said is not applicable to indoor painting.

White lead is injuriously acted upon by the action of
sulphureted hydrogen vapors, which will quickly turn
it black. That gas converts it into the black sulphide of
lead. This will sometimes occur m a single night, there-
fore its use should never be resorted to in localities where
this gas is likely to develop.

There is one grade of white lead which is best known as
flake white. It differs in no wise from ordinary lead
excepting in that it is a selected white lead. The flakes
which drop off the buckles corroded by the stack system,
have given it the name. This outer covering of the
buckles is superior in opacity to that from which the
flakes fell off and which comes next to the core or uncor-
roded lead that is more imperfectly corroded, and which
in ordinary lead is averaged with the flakes and forms the
white lead of commerce. Therefore flake white desig-



WHITE PIGMENTS 23

nates a quality of white lead of superior corrosion and
which possesses extra good body.

The same objectionable features enumerated as apper-
taining to ordinary white lead, apply to this with as
much force. It is used mainly by decorators and sign
painters for striping in car shops and carriage factories,
for coaches, buses and wagons, in fact, wherever an
extra good-bodied lead is demanded.

Every nation has its own system of packaging, grading
qualities and marketing white lead, therefore one will not
find the same rules nor trade customs in the United States
as prevail in the United Kingdom, nor upon the continent
of Europe.

In the United States an unwritten law has developed
which says that upon all packages on the label of which
the manufacturer's name is placed and the words
" Strictly Pure" are used that the contents of the
package are free of any adulterating material and
contain nothing but pure white lead ground in pure
linseed oil.

It is, however, true that some jobbers mark some fake
leads as strictly pure, which are far from being so and which
are adulterated to the bitter end; but then, they withhold
from them their own names and adopt some flaring name
or label which misleads no one aside from the unsophisti-
cated and ruralists who wish to buy pure lead at half its
market value.

So if a lead package put up in the -United States bears
no corroder's name nor the legend " Strictly Pure" upon
it, one may take an oath and swear that its contents are
adulterated. He can do so without ever having seen an
analysis of it, and without the least fear of committing
perjury. None such is pure. It is an adulterated lead,
or what is known as a compound lead.



24 MODERN PIGMENTS

It is not within the province of this treatise to enter
into an endless review of the merits or demerits of com-
pounded leads, nor of the superiority and better wearing
qualities claimed for them by their manufacturers over
that of the strictly pure.

There can be little doubt, that proper combinations of
other pigments with white lead are beneficial for many
purposes. The painter should be well enough posted to
do this compounding himself to suit the particular job
upon which the compound is to be used. Certain com-
pounds or combinations of pigments are better adapted
to sundry conditions than they are to any other; and no
ready-prepared compound, even when honestly made
after a uniform formula, is likely to meet his requirements
fully in this regard, however good it may be for the right
place.

A man well posted upon the various qualities and
defects of the white pigments should be able to pick out
the proper corrective ones to combine with white lead to
suit any job. If it be old, open or spongy, it certainly will
require to be treated differently from a surface which is
close or non-absorbing.

There are, no doubt, very good lead compounds upon
the market which will give desirable results for painting
under certain conditions to which they are admirably
adapted, but which will cause some trouble and always
mortification elsewhere. As a rule, there is no real
advantage to be gained from their use. They are not
as economical as those similar in composition and com-
pounded at the shop from strictly pure white lead and
other correctives bought as such.

Barytes, or the native barium sulphate (heavy spar),
plays an important function as an adulterant of white
lead ; for that matter, it does in the adulteration of nearly



WHITE PIGMENTS 25

all other pigments. But it is preeminently adapted as
a makeweight for white lead: its heavy weight comes
nearest of any other to that of white lead. Its trans-
parency, too, in oil is another reason why that substance
is so well adapted for the purpose of its or any pigment's
adulteration, because it will not discolor them. More
will be said regarding barytes under its proper heading,
and the reader is referred there for the particular details
and characteristics belonging to that pigment. The one
object why it was entered into here is because it was
necessary to point out the main source of adulteration in
connection with the "off brands" of white lead as are
best known and called all brands of lead that are not
strictly pure. Compound leads which are sold as such,
are not included in the "off brands," but are known in
the trade as "compounds."

Compound leads are not necessarily adulterated leads,
because in the first place they do not claim to be strictly
pure lead. They are legitimate articles of commerce,
and stand upon their own merits. Painters buy them
with a full knowledge of what they are, and from having
had some previous experience with them, which in some
instances has been well paid for.

The same substances which may be used in a legitimate
way in a compound lead, and of whose presence the buyer
is well aware, may be and are rightly called adulterants
when combined with lead which the purchaser is led to
suppose is pure white lead.

For this reason, gypsum, china clay, carbonate
of lime, or even the sulphate of lead, which are all
used in the adulteration of white lead, are not such
when the purchaser buys a compound lead, as the
attempt is not made to parade them as something which
they are not.



26 MODERN PIGMENTS

LEAD SULPHATE

This lead salt is never sold under that name in the
supply stores. It is only within a comparatively short
time that it has come to be talked about in connection
with paint or mixtures of paint.

It is a by-product of several industries, and until lately
it has had but little commercial value other than that
which inherently belongs to it, as, if it could be
reduced to its metallic form, it would be worth the price
of metallic lead less the cost of conversion, which is
expensive.

It can be readily made by simply adding sulphuric
acid to the solution of a lead salt; then it becomes^ pre-
cipitated as a white powder which is insoluble in water
and absolutely so in alcohol.

Its insolubility makes it non-poisonous. If it pos-
sessed a good body, or, in other Words, had it more opa-
city, it would be a very, desirable pigment^ It is not as
pure toned a white when ground in oil as is white lead.
It is not readily affected by the vapors of sulphureted
hydrogen. Its chemical formula is PbSO 4 .

Sulphate of lead is never used alone as a pigment, but
as an adjunct to some brands of white lead, and largely
so in ready-mixed paints. Its chief use in paint mate-
rial manufacture is for such grinders as put out a brand
of white lead which they mark as strictly pure. It
enables them to place a product upon the market for
which they can vouch as strictly pure lead, but is no
more entitled to be so called than sugar of lead would
be. When sold as "strictly pure" lead, sulphate of lead
is as much entitled to be called an adulterant as barytes,
other substances which have no business to be



WHITE PIGMENTS 27

It is used advantageously in color making such as the
lemon or canary chrome yellow but in the above they
are really the result of the use of sulphuric acid in
the making of the color, and not because they are placed
there.

SUBLIMED LEAD

Sublimed lead is a certain form of sulphate of lead
which is obtained by sublimation in Southwestern Mis-
souri, and to which much of what was said of sulphate
of lead proper does not apply. While it is still somewhat
deficient in opacity as compared with hydro-carbonate
white lead, it comes next to it in that respect, and is
used extensively by mixed-paint manufacturers in pre-
paring those goods.

It is basic sulphate of lead; contains about one fifth
of lead oxide and about five per cent of zinc oxide the
ores from which it is made containing zinc in combination
with the lead. It is sublimed in a manner somewhat
similar to that described under tne heading of Zinc White.

One property entitling it to consideration is its non-
poisonous character. Another good point is that being
an oxysulphate of lead it is not subject to turning black
by sulphureted hydrogen gases, and is so extremely fine
that it does not settle readily in an oily vehicle. It is
also very white when mixed in oil, which cannot be said
of sulphate of lead.

DAHL PROCESS WHITE LEAD

This form of lead pigment is obtained by precipitation.
By a modified method of manufacture, it is much superior
to the product obtained originally. In this modified
process it is first reduced to a downy or feathery state,
after which it is placed in stationary tanks where it is sub-



28 MODERN PIGMENTS

jected to the action of dilute acetic acid which converts
it into a basic acetate of lead. The solution is subjected
to the action of a stream of carbonic acid, which, as already
said, lead having more affinity for it than it has for acetic
acid, combines with it, and is precipitated in the form of
basic carbonate of lead.

It differs from Dutch and similar process leads in that
instead of being crystalline it is amorphous in its par-
ticles. It therefore does not possess quite so much
opacity, but is a greater absorbent of linseed oil. Natu-
rally from its amorphousness it is very fine, and runs
uniform in composition. It is, however, too soon to form
a decided opinion of its merits, whatever it may present
theoretically.

WHITE OXIDE OF LEAD.

Periodically somebody or other discovers or rather
thinks he does something new in a white pigment of
lead derivation which in his estimation is sure to
displace the hydrate oxide of lead, and that his discovery
is sure to fill the "long felt want" of a pigment one
that is white, non-poisonous, not injured by noxious
gases, and for which they claim a string of virtues too good
to be true and too numerous to mention. These great
discoverers appear as regularly as the seventeen-year
locust, and the wreckage of the last of them is hardly
cleared away before somebody else turns up ready to
launch out a new venture which proves similar to the
ones which have gone before; but as it is launched
out under a new name, it takes a little time before it is
recognized.

It seems that some people will never learn that oxides
of lead all have the property of solidifying into a hard



WHITE PIGMENTS 29

mass inside of the package containing them in the shape
of a ground paste, if ground with linseed oil. Yet one
after another of the discoverers seems to be able to enlist
men with capital to back their foolish ventures, and men
of good business capacity and caution in other respects
try to accomplish the impossible i.e., grinding lead
oxides with linseed oil.

The white oxide, the monoxide (litharge), the bioxide
(red lead), the teroxide (orange mineral), all have the
same peculiarity of solidifying in time when ground in
linseed oil. When the retailers who are not posted, have
keg after keg returned to them after a few months
with occasionally a claim for damages it proves to be
the beginning of the end for " oxide of lead " in that
locality.

Some in sheer desperation have gone so far as to grind
it in soft linseed oil soap, as, when ground in that, it
remains in a smooth, soft paste; but, as one could readily
expect, it is soon found out and the " jig is up." The
history of defunct concerns in this connection would make
good reading on short-sightedness for the rising generation.

There have been, and some firms are to-day trying,
experiments with other salts and forms of lead. Time
may prove some of value; none so far have any claim
to superiority over the old hydrate-carbonate. All as
yet have so many defects that the very grave ones
admitted as belonging to white lead look small compared
with them.

The Blowpipe Test

Adulteration in white lead and many other forms of
lead is readily detected by the use of the blowpipe.
This simple test is within reach of every paint dealer or
painter. It is simple and easily made: A piece of soft
charcoal, such as is made from willow, to lay the lead upon,



30 MODERN PIGMENTS

an ordinary candle or spirit lamp, and a blowpipe. This
is simply a small metal tube curved at the end. The*
curved end has a very small aperture, and that is placed
against the flame of the candle while the operator blows
in the other end of it; this throws a stream of blue flame
from the candle to the charcoal, or to that part of it
rather where the lead is laid upon it, the operator holding
the piece of charcoal in his left hand. The blowing
should be regular and steady, and in a minute or two
at most the oil will be burned out, and the white lead
will be converted into a blue lead globule.

If it has been adulterated with lead sulphate, barytes
or whiting, china clay, etc., the lead cannot be reduced
to a metallic state by any amount of blowing. There
will be a mass of dry white, yellowish or grayish color
according to the adulterant, but no lead will show up.
As small a percentage as 10 per cent of adulteration
mixed with the lead will prevent its reducing; as no
lead is ever adulterated with such a small percentage
as . that, there will be no difficulty in finding it with the
blowpipe.

If the adulterant is sulphate of lead, it can be found by
the great difficulty of its reduction; few men can use the
blowpipe steady or long enough so to reduce it, as it
takes much more heat to do so. That form of it men-
tioned as sublimed lead is practically irreducible by the
blowpipe; it takes over 1200 F. So one may look with
suspicion upon any white lead that does not readily
reduce in two minutes.

One can form a good idea of the purity of lead by putting
a little of the lead paste upon a sliver of pine wood, and
burning a match or two underneath it. If it is pure, little
globules of metallic lead will appear in the paste, which
will not be the case if the lead is impure.



WHITE PIGMENTS 31

The blowpipe test is valuable only to test the purity
of hyd-oxi-carbonate of lead the white lead of com-
merce. It will not apply to many of the white salts of
that metal, as some fuse only at extreme temperatures
or by the use of fluxes which none but experienced men
can conduct successfully.

The present tendency in some quarters to recognize as
" white lead/' in a commercial way, the basic sulphate
of lead or sublimed lead would of course nullify the test;
but why, if, as claimed, oxy-sulphate of lead is superior
to Dutch process hyd-oxi-carbonate the standard white
lead of commerce should it seek to shelter itself under
the name adopted for an entirely different pigment?

Will it not be better for both to retain their present
designations which have a definite meaning, and if sub-
limed lead proves itself the superior, it should be entitled
to a distinctive name by which purchasers can purchase
it with a certainty that it has not been adulterated with
Dutch process lead, and it should not seek to shelter itself
under its time-honored appellation?

The above is written not as a disparagement or as an
indorsement of one or the other forms of leads, but in
hope of saving the white lead and sublimed lead indus-
tries from future confusion, whereas now the two are
distinctly known and recognizable under their commercial
cognomen.



CHAPTER III
WHITE PIGMENTS (Continued')
ZINC WHITE
History

V /

ZINC WHITE as a pigment is of much more recent origin
than that of white lead, and does not date back much
farther than threescore and ten years. It was known
before that, and it had been used in water colors a few
years previously. As an oil pigment, however, it may be
called a recent one. It would in all likelihood have been
used for years before it was, but for the difficulty en-
countered in making it dry properly; and writers in the
beginning of the nineteenth century incidentally mention
the probability and possibility of its becoming a useful
pigment. However, it was in the forties that it was first
used as an oil paint with a drying oil by Leclaire in France.
From that time to the present, its use has steadily grown
and extended.

It took a long while at first to break down the pre-
judices then existing against its use, and which even now
prevent many from using it. So the advent of this pig-
ment to popularity has been slow. It has had a hard
time to establish itself firmly.

Chemistry and Manufacture

There are two very distinct qualities of zinc white.
The better quality is known to the trade as " French"



WHITE PIGMENTS 33

zinc, and the other as " American" zinc; both have the
same chemical composition, oxide of zinc.

French zinc is that which is made from the zinc metal,
while American zinc so-called is made directly from the
zinc ore. It will be seen that the terms used to designate
these two qualities are more arbitrary than strictly
true at least, such is the fact to-day. It does not do
America justice to call the poorer zinc after it, but, as we
have seen in the case of Cremnitz white, names stick. No
amount of reasoning is likely to change it any more than
in another glaring instance, i.e., English and American
Venetian red.

The French are no doubt entitled to the honor of
having first used this valuable pigment; also of having
first produced it in a commercial way; so that importers,
brokers, and paint manufacturers gave it the name, and
habit still forces the name to remain. France never had
a monopoly of its manufacture, and Belgium produces
one of the most esteemed of its brands the " Vielle
Montagne" zincs.

Within the past twenty or twenty-five years, works
have been established in the United States which are
producing zinc oxide by the "French" process which is
certainly equal in quality to that made in any country.
It is sold as ''French " zinc, and the grinders pay as good
a price for it as for that which is imported.

The process of manufacturing zinc white is very sim-
ple. The metal is vaporized by heat in retorts, whence
it is carried to a chamber where the vaporized zinc comes
in contact with air containing oxygen, for which
element it has a great affinity. It combines with the
oxygen, and is at once converted into an oxide of zinc.
This oxide of zinc is gathered into a series of sacks or
small chambers suspended with the mouths opening



34 MODERN PIGMENTS

downward. That which is lightest and whitest is
deposited farthest from the point of entrance of the
vapor; the heavier is also the darker and is deposited
nearest. This darkness is caused by impurities con-
sisting mainly of unconverted metal, which prevent the
grading of the zinc white as first quality.

Zinc oxide made thus is very light and flocky,
resembling in a manner snow or eiderdown. It is
selected and graded according to quality, whiteness,
etc.; after which it is submitted to the action of
powerful compressing machinery under intense heat;
then it becomes the article of commerce known as
"Dry Zinc White."

Vast quantities of it are annually consumed in that
shape for distemper work, for the better class of kalso-
mining, etc.; either alone as a white, or in combination
with whiting or gypsum or with coloring matter in the
making of certain tints.

For use in linseed oil painting, it is ground either in a
strong drying oil which has been previously treated to
discolor it, or in drying poppy seed oil for the finer grades
of work.

It is usually packed in tin cans ranging from one to
twenty-five pounds each. Both the French and the
American zincs are sold in two qualities according to
their whiteness. The whitest and best is sold as Green
Seal zinc white, while that which is of a darker shade is
sold as Red Seal. These are usually found in the output
of all grinders of zinc, and they have come to be under-
stood as meaning first and second quality. They are
used upon all grades of zinc ground in linseed oil or poppy
seed oil, except upon the very lowest and cheapest grades
of American zincs, which, in addition to being of poor
zinc, are usually adulterated.



WHITE PIGMENTS 35

American zinc is made in precisely the same manner as
that described for French zinc, with the exception that
instead of using zinc metal, zinc ore is employed in its
place. It is made from the vaporization of the ore, the
oxidation being the same; the process in all respects being
identical, and so are the after treatments.

From the impurities contained in the ore, one may well
surmise that the product cannot be equal in either white-
ness or quality to that made from the metal itself. Both
systems are now used in the United States, but, as stated
before, it is only in recent years that it has been made
here from the metal.

The chemical formula of zinc white is ZnO. It is the
only oxide of that metal and the only one of its many
salts that is of any use as pigment to the painter.

Tests for Purity

The purity is easily tested. If it is in a dry powder,
it will dissolve readily without effervescence in either
dilute nitric or hydrochloric acid.

If it has been adulterated with barium sulphate, that
substance will not be acted upon by the acids. It will
be left undissolved in the shape of a white powder at the
bottom of the dish. If there is effervescence during the
dissolving of the zinc white by the acids, the presence of
lime in the shape of carbonate of lime or whiting is plainly
indicated.

If the zinc to be tested is ground in oil or varnish, it
should be agitated thoroughly in benzine or naphtha,
which will dissolve the linseed oil out of it. Let it rest
and deposit after the agitation has been thoroughly done,
then pour out the benzine and repeat the same operation
until it is thoroughly free from the oil. After drying the
powder which will be done quickly if left in the open



36 MODERN PIGMENTS

air it can be used in the test precisely as was described
for the dry zinc white.

Zinc white is not affected by sulphureted hydrogen
gases, nor by sulphurous vapors of any kind.

Properties and Uses

Oxide of zinc, or zinc white as it is best known to the
paint trade, has had its praises sung to all kinds of tunes