TECHNICAL INFORMATION OIT BUILDING MATERIALS

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FOR USE IN TEE DESIGN OF LOW-COST HOUSING

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THE NATIONAL BUREAU OE STANDARDS

UNITED STATES DEPARTMENT OE COMMERCE

WASHINGTON , D. C.

Aiyrast 13. 19 5^

PAINT PIGMENTS—WHITE

This is primarily a digest of the sections of Biireau of Standards

Circular No. 69 , "Paint and Varnish", (November 17 , 1917) > and Technologic Paper No. 274, "Use of United States Government Specification

Paints and Paint Materials", (December 15 , 1924) ,2 by P. H. Wallcer and

E. E. Eichson, dealing with common names, general composition, manufacturing processes, characteristics and uses of white pigments and

extenders.

The following papers contain additional information relative to

paint pigments, oil paints, and water paints:

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"Paint Pigments—-Black, Red, and Lakes"

"Paint Pigments—-Yellow, Brown, Blue, Green, and

Bronze"

"Eederal Specification Paint Pigments and Mixing

Eormulas"

"Federal Specification Ready-Mixed Paints, Semipaste Paints and Mixing Eormulas"

"Preparation of Paints from Paste and Dry Pigments"

"Preparation of Paints from Semipaste Paints,

Thinning Ready-Mixed Paints and Preparation of

Water Paints"

"Aluminum Paints"

Pigments are "the fine solid particles used in the preparation of paint,

and substantially insoluble in the vehicle". 3 In general, it may be

^Out of print. May be consulted in Government depository libraries.

^Available from Superintendent of Documents, Government Printing

Office, Washington, D. C. (Price 10 cents).

^Quoted from "Standard Definitions of Terms Relating to Paint

Specifications", American Society for Testing Materials (1933)

PP- 735-733.

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assumed that pigments composed of very fine particles , having high

refractive indices, provide the greatest covering power and opacity.

Classes of Pigments in General Use :

Body Pigments’ are those which constitute the hulk of the pigment

present and give to the paint film its characteristic properties.

Color Pigments are those used primarily to produce a decorative

effect.

Extenders are substances possessing few, 'if any, of the properties

required for body pigments; but which are frequently added to paints,

in many cases without harmful effect, because of their cheapness or to

impart some particular properties peculiar to them*

Federal Specifications are specifications adopted by the Federal Specifications Executive Committee and approved by the Director of Procurement,

Treasury Department, for use of all departments and establishments of the

Federal Government.

Basic Carbonate White Lead

Common Karnes ; Basic carbonate white lead is also known as white lead,

corroded lead, corroded white lead, carbonate of lead, basic lead car- bonate, hydrate of lead, hydro carbonate of lead, lead carbonate, car- bonate white lead, and lead.

Types, Production and Characteristics:

Old Hutch Process basic carbonate white lead is prepared by cor- roding metallic lead with fermenting tan bark and dilute acetic acid

forming a white flaky substance which is crushed, screened, ground in

water, and either dried to form dry white lead or ground in oil without

drying t’o form pulp mixed white lead. It is composed of very dense

and opaque, fine and coarse particles, which possess great hiding

power, and work very smoothly when ground in oil as paint.

Carter Process : This process of manufacturing basic carbonate white

lead is the same as the Old Dutch process, except that melted lead is

first converted into a granular dust and corroded by dilute acetic acid

and carbon dioxide. Carter process white lead is usually whiter, finer,

and less dense and opaque than that made by the Old Dutch process. The

particles are also more uniform in size.

^Copies of all Federal Specifications mentioned in this digest may

be obtained from Superintendent of Documents, Government Printing Office,

Washington , D, C. (Price 5 cents each).

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Precipitation Process : In this process, lead is dissolved in acetic

acid in the presence of air, producing a “basic acetate solution from

which the basic carbonate is precipitated by carbon dioxide. Precipitated white lead is even finer than that produced by the Carter 'process.

Electrolytic Process ; In the Sperry process, used in this country,

a lead anode surrounded by a solution of sodium acetate is used-, and

the cathode is surrounded by sodium carbonate solution. Lead is dissolved

from the anode as lead acetate and precipitated as basic carbonate by the * sodium carbonate.

General Composition : Basic carbonate white lead is regarded as consisting of two equivalents of lead carbonate and one of lead hydroxide.

The commercial product should not vary widely from this composition even though made by different processes.

Use : White lead is the most important of the white pigments. It enters

into most light-colored paints, and is the only white pigment that can be successfully used alone in white linseed oil paints intended for outdoor exposure. While both basic carbonate and basic sulphate can be

used, the former is generally preferred. The basic sulphate finds its

greatest use in ready-mixed paints.

Characteristics of White Lead Linseed Oil Paints: These paints spread

and hide well,. -and dry to somewhat soft films which do not generally

decay by cracking, but do chalk—a condition generally satisfactory

for repainting. Owing to the soft nature of. white lead Linseed oil

paint surfaces, they show a greater tendency to take up dirt than is

the case of harder paint films.

Federal Specification ; See TT-W-251a, "White Lead; Basic-Carbonate,

Dry, Paste-In-Oi'l", and Semipaste containing Volatile Thinner."

Basic Sulphate White Lead

Common Fames: Basic sulphate white lead is frequently sold under the

trade name "Sublimed White Lead" , and is sometimes called basic sulphate

of lead, sublimed lead, basic lead sulphate, sulphate of lead, or white

lead.

Production : It is produced by heating a mixture of powdered anthracite

coal and lead sulphide ore in the presence of air which vaporizes and

sublimes the lead sulphide as a basic lead sulphate. Ores used in making

this pigment always contain some zinc.

General Composition: The pigment usually contains about 15 percent lead

oxide, about 5 percent zinc oxide, and 80 percent lead sulphate. A

sublimed white lead is also being made today which is free from zinc

oxide, containing about 75 percent lead, sulphate and 25 percent lead

oxide.

Characteristics: Basic sulphate white lead is very fine grained, ex- ceedingly white in color. Its hiding power is slightly less than that

of basic carbonate white lead.

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Federal Specification: See TT-W-26l , "White Lead; Basic Sulphate, Dry

and Faste-In-Oil

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Zinc Oxide

Common Fames; Zinc oxide is also known as oxide of zinc, zinc white,

white zinc, and zinc.

Types, Production and Characteristics:

French Process zone oxide is -prepared "by collecting zinc oxide

particles formed hy heating metallic zinc in a current of air. The

finest and whitest particles weighing l^O pounds per "barrel aro graded

as White Seal. The coarser particles weighing 3OO pounds per "barrel are graded as Green Seal, and Red Seal.

American Process zinc oxide is prepared "by heating a mixture of

zinc ore and anthracite coal as in the manufacture of "basic sulphate

white lead. This product is similar to French process zinc oxide, hut

generally not so white and it may contain small amounts of lead compounds.

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Zinc oxide can he used alone in a varnish vehicle for the manufacture

of high grade enamel paints. It should not he used alone in oil paints

intended for outdoor exposures. Some so-called zinc oxide ,cil -paints 'intended for outdoor exposures are available commercially. However, those

which prove to he most satisfactory always contain large proportions of

other pigments, generally white lead, or a mixture of white lead and

titanium pigments.

With mildly chalking pigments such as white lead, the hardening

effect resulting from mixing them with zinc oxide is distinctly beneficial. In the case of badly chalking pigments such as titanium oxide,

it is necessary to add zinc oxide to produce satisfactory paints.

For preparing mixed pigment oil paints for general use, either

American process or leaded zinc oxide may he used. French process zinc

oxide is preferred for making white enamels, lacquers, printing inks,

etc. According to modern tests, French process zinc oxide should not

he used in exterior oil paints.

Characteristics of Zinc Oxide Oil Paints; Zinc oxide in oil, unless

mixed with white lead and inert pigments, forms a paint that dries to a hard film which is liable to crack rather than decay hy chalking.

Federal Specification; See TT-Z- 3OI, "Zinc-Oxide; Dry and Paste-In-Oil."

Leaded Zinc Oxide

Production ; Leaded zinc oxide is prepared hy a method similar to that

used in producing American process zinc oxide, using bituminous coal

and carbonate sulphide zinc ores that may contain lead in any proportion up to an amount equal to that of the lead present.

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Characteristics and Use: It is very fine grained, possesses fair hiding

power, "blit is not -so white as American process zinc oxide. Leaded zinc

oxides are used principally in the manufacture of prepared and paste

paints. They appear to impart good durability and good tint retention

to exterior house paints. j

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Federal Specification.; See TT-Z-321 , "Zinc Oxide; Leaded, Dry and

Paste-In-Oil."

Lithopones

Common Fame s: Lithopone is also known as Ponolith, Orr's white, Beckton

white., Griffith's white, etc.

Production ; It is produced by grinding, drying, and powdering the

calcined precipitate of 'barium sulphate and zinc sulphide resulting

from the addition of a solution of barium sulphide to an equivalent

solution of zinc sulphate.

General Composition : Best grades of lithopones contain nearly JO percent

zinc sulphide, a little zinc oxide, and the balance barium sulphate.

High strength ( 50 $ zinc sulphide) lithopones, as well as zinc sulphide,

and titanated lithopone containing 15 percent titanium oxide and SJ

percent lithopone, are also available today. Ground barytes are added

in the lower grades.

Characteristics ; Well-made lithopone is very white in color, and very

fine in texture. Formerly, some lithopones darkened on exposure to

bright light while others retained their color. The modern lithopone

is light resistant.

Use : Lithopones are extensively used in paints for inside work, especially

in flat wall paints, and enamels. Regardless of the unstable condition

of zinc sulphide, it is sometimes usee successfully when mixed with basic

carbonate white lead. Lithopone is also used to some extent in exterior

paints, although the present trend is to use zinc sulphide mixed with

leaded zinc oxide and siliceous extending pigments.

T i tanium Figment

s

Varieties and- Compositions : Titanium white pigments are available in

three varieties; titanium oxide, containing nearly 99 percent titanium

oxide, calcium-base titanium pigment, containing 7^ percent calcium

sulphate and JO percent titanium oxide, and barium-base titanium pigment

containing 75 percent blanc fixe and 2J percent titanium oxide. A

recent siliceous base- tl tanium , pigment , containing JO percent -siliceous

pigments and JO percent titanium oxide has also appeared on the market.

Characteri sties ; Titanium pigments are extremely opaoue , very white in

color, and composed of particles very fine in size. The straight titanium

oxide is outstanding among the white pigments for its extreme opacity.

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Use: These pigments are becoming, very important in outside white paints,

interior flat wall .paints , .and interior gloss enamels. In outside white

paints, the barium-base .titanium pigment is generally used, being mixed

with white lead and. zinc oxide.

Federal Specifications: See TT-P-lOla, "Paints; Titanium-Zinc-Lead and

Titanium-Zinc, Outside, Ready-Mixed, White,"

Slaked Lime (Calcium. Hydroxide)

Production: Slaked lime is produced by the action of water on quicklime

or calcium oxide.

Use: The use of slaked lime as a paint pigment is confined to water

paints, particularly whitewash.

Barium Sulphate

Forms ; Barium sulphate is an important extender, and is known as "barytes"

when obtained by grinding mineral baryte or heavy spar which is crystalline

and coarse in structure, and settles out from the paint vehicle. The

precipitated form .'known as "blanc fixe" is much finer and stays up better.

Characteristic s : It is extremely stable, practically colorless when mixed

in oil, possesses little hiding power, does not react with any paint

making material, and is not affected by gases or vapors found in air.

Use

:

Barium sulphate is extensively used as the base upon which colors

are precipitated to. form lakes. It is also useful for diluting highly

colored pigments without modifying the tone.

Silica (Silex) Silicon Dioxide

Forms : Silicon dioxide is another extender in common use. When obtained

by crushing and grinding quartz rock, chert, flint, sand, etc.

,

it is

composed of very fine sharp particles, and is inert and white, but without hiding power. This form is valuable for use as a base in paste wood

fillers, and to provide "tooth" to paints, that is, power to take hold

and adhere to wood surfaces.

The second form, known as diatomaceous earth or kieselguhr—

a

natural deposit of skeletons of microscopic organisms called diatoms

has less "tooth" than ground quartz.

Magnesium Silicate

Production : Magnesium silicate known as "Asbestine" is obtained by

grinding waste asbestos.

Characteristics: It is a white pigment of low specific gravity, and

more or less fibrous in structure.

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Uses Magnesium silicate is used largely for mixing With other pigments

to prevent them from settling out of the paint while standing in the

container. Other magnesium silicates, such as soapstone, are also ground

and used to some extent in paints. They are, however, inferior to ground

asbestos in that they do not so effectively prevent the pigment from

settling out of the paint.

Kaolin or China Clay

General Corn-position: Kaolin is hydrated aluminum silicate.

Uses It is largely used in so-called dipping paints to prevent pigments

from settling out in the tanks, and as the inert base upon which colors,

especially para reds, are precipitated as "lakes".

Gypsum (Terra Alba)

Gene ral Cr-m no sition ; Gyusum is hydrated calcium sulphate.

Forms 5 When calcium sulphate is heated to about 185° C, part of the water

is driver, off, leaving plaster of Paris, which can absorb water and set.

If all the voter is driven off by further heating, "dead burnt" calcium

sulphate is formed, which does not readily take up water. The "dead

burnt" form is used as an extender in Venetian red.

Calcium Carbonate (Natural Chalk)

Grades : natural chalk is ground, levigated, and graded according' to

fineness and whiteness into "Paris white", and "gilders' whiting"

.

These are very fine and bulky, and used in paints to aid in the sus- pension of the pigment and to neutralize acidity. Commercial "whiting",

a third grade, is used in calcimine and putty. A surface treated

calcium carbonate, having some unusual properties, is available to the

paint manufacturer.

Marble Dust

Characteristics and Use: Marble dust is crystalline. It provides

"tooth" to paints, but settles out too readily to make its use desirable,

except in priming. It is sometimes added to putty to make it work "short"

Ground limestone is similar to marble dust, hut likely to he less pure.

Precipitated Chalk (Alba Whiting)

Characteristics and Use: It is very white, extremely bulky, and may be

used instead of Paris white or gilders' whiting.

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