PAINT TECHNOLOGY AND TESTS

PAINT TECHNOLOGY
AND TESTS.

BY

HENRY A. GARDNER

Assistant Director, The Institute of Industrial Research, Washington, D. C.
Director, Scientific Section, Paint Manufacturers’ Association of the United States, etc.

McGRAW-HILL BOOK COMPANY
239 WEST 39TH STREET, NEW YORK
6 BOUVERIE STREET, LONDON, E.C.
1911

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Copyright, 1911, by the McGraw-Hill Book Company

THE·PLIMPTON·PRESS·NORWOOD·MASS·U·S·A

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TO
MY MOTHER

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PREFACE

A few years ago the producer and consumer of paints possessed comparatively little knowledge of the relative durability of various pigments and oils. There existed in some cases a prejudice for a few standard products, that often held the user in bondage, discouraging investigation and exciting suspicion whenever discoveries were made, that brought forth new materials. Such conditions indicated to the more progressive, the need of positive information regarding the value of various painting materials, and the advisability of having the questions at issue determined in a practical manner.

The desire that such work should be instituted, resulted in the creation of a Scientific Section, the scope of which was to make investigations to determine the relative merits of different types of paint, and to enlighten the industry on various technical problems. Paint exposure tests of an extensive nature were started in various sections of the country where climatic conditions vary. This field work was supplemented in the laboratory by a series of important researches into the properties of pigments, oils, and other raw products entering into the manufacture of protective coatings. The results of the work were published in bulletin form and given wide distribution. The demand for these bulletins early exhausted the original impress, and a general summary therefore forms a part of this volume.

The purpose of the book is primarily to serve as a reference work for grinders, painters, engineers, and students; matter of an important nature to each being presented. Without repetition of the matter found in other books, two chapters on raw products have been included, and they present in condensed form a summary of information that will prove of aid to one who desires to become conversant with painting materials with a view to continuing tests such as are outlined herein. In other chapters there has been compiled considerable matter from lectures and technical articles presented by the writer before various colleges, engineering societies, and painters’ associations.

The writer wishes to gratefully acknowledge the untiring efforts of the members of the Educational Bureau of the Paint Manufacturers’ Association, whose early endeavors made possible many of the tests described in this volume. Kind acknowledgment is also made to members of the International Association of Master House Painters and Decorators of the United States and Canada, who stood always ready to aid in investigations which promised to bring new light into their art and craft.

HENRY A. GARDNER.

Washington, October, 1911.

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CONTENTS

CHAPTER PAGE I  Paint Oils and Thinners 1 II  A Study of Driers and Their Effect 21 III  Paint Pigments and Their Properties 42 IV  Physical Laboratory Paint Tests 70 V  The Theory and Practice of Scientific Paint Making 93 VI  The Scope of Practical Paint Tests 105 VII  Conditions Noted at Inspection of Tests 114 VIII  Results of Atlantic City Tests 124 IX  Results of Pittsburg Tests 135 X  A Laboratory Study of Test Panels 149 XI  Additional Tests at Atlantic City and Pittsburg 174 XII  North Dakota Paint Tests 182 XIII  Tennessee Paint Tests 201 XIV

class="left"> Washington Paint Tests 207 XV  Cement and Concrete Paint Tests 214 XVI  Structural Steel Paint Tests 220 XVII  The Sanitary Value of Wall Paints 252

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PAINT TECHNOLOGY

CHAPTER I

PAINT OILS AND THINNERS

Constants and Characteristics of Oils and Their Effect upon Drying. An attempt has been made to give in this chapter a brief summary of the most important characteristics of those oils finding application in the paint and varnish industry. For methods of oil analysis, the reader is referred to standard works on this subject; the analytical constants herein being given only for comparative purposes.

It is well known that one of the most desirable features of a paint oil is the ability to set up in a short period to a hard surface that will not take dust. This drying property is dependent upon the chemical nature of the oil. If it is an unsaturated compound, like linseed oil, rapid absorption of oxygen will cause the film to dry rapidly and become hard. If the oil be of a fully satisfied nature, like mineral oil, oxygen cannot be taken up to any great extent and drying will not take place. The various animal and vegetable oils differ in their power of oxygen absorption to a lesser or greater extent. This difference is referred to by the chemist in terms of the iodine value. The iodine value of linseed oil is approximately 190, meaning that one gram of the oil will take up 190 centigrams of iodine. Oils with high iodine values have good drying powers, while those with low iodine values are, as a rule, very slow drying in nature.

For a description of the working and drying properties of various oils used in paints, see Chapter XIV. The oxygen absorption of various oils and mixtures is shown in Chapter II.

Linseed Oil. The seed of the flax plant which is extensively grown in North Dakota, Argentine Republic and Russia, contains approximately 36% of oil which may be obtained by grinding, heating, and expression. Ripe native seed generally produces a pale oil of little odor; the oil from Argentine seed often having a greenish tint and an odor resembling sorghum. While filtering, pressing and ageing will remove considerable of the (“foots”) mucilaginous matter, phosphates, silica, etc., from the oil, the better grades which are intended for varnish making are often refined with sulphuric acid. A light colored oil which may be heated without “breaking” results from this treatment, but such oils are apt to contain considerable free fatty acid, unless they are washed with alkali subsequent to the sulphuric acid treatment. On account of its rapid drying properties and general adaptability for all classes of paints and varnishes, linseed oil has never been supplanted by any other oil. Chemically it consists of the glycerides of linoleic, oleic, and isolinoleic acid, its constitution being responsible for its very high iodine value.

Boiled linseed oil, a heavier and darker product, is made by heating the raw oil in open kettles to high temperatures, generally with the addition of metallic driers such as litharge, and black manganese. The resinates of lead and manganese are often added to oil heated at a lower temperature, to obtain a boiled oil of lighter color.

By blowing air through linseed oil that has been heated to approximately 200 degrees Fahrenheit, either with or without drier, heavy bodied oils are obtained, which find special application in varnishes and technical paints. As the viscosity of these oils increase, the iodine values decrease, and a slight rise in saponification value and

specific gravity is observed. The following analyses of various types of linseed oil were recently made by the writer:   Pure Raw
Linseed Oil Boiled
L. O.
(Linoleate) Boiled
L. O.
(Resinate) Blown
L. O. Litho.
L. O. Old
Treated
Oil Color Amber Dark Reddish Pale Dark Amber Clear Brown Brown   Brown Clear Sp. Gr. at 15° C. .933
Average .941 .930 .968 .970 .943 Iodine No. 180 172 176 133 102 172 Saponification No. 191 187 186 189 199 197 Free Fatty Acid 3.2 2.7 2.2 2.8 2.7 6.9 Unsaponifiable 1.4 — — — — 1.8 Maumene 111 — — — — 96 Moisture .2% — — — — none

Soya Bean Oil. The soya plant which is extensively cultivated in Asia produces a seed bearing up to 22% and over of a golden colored oil having a peculiar leguminous odor. The oil, which probably consists of the glycerides of oleic, linoleic, and palmitic acids, is secured by crushing, steaming and pressing the seed. There are several varieties of the plant, and they are said to be the best annual legume for forage, the straw and fruit being rich in nitrogen and very fattening as a cattle food. Soya may be grown in nearly any country and is a great carrier of nitrogen to land deficient in this element. Although the oil has been used abroad for many years for soap-making purposes, its use as a drying oil is comparatively recent; being introduced into the paint industry of the United States during the year 1909, when linseed oil started on its phenomenal rise in price.

The oil has given fair service in some paints when mixed with upwards of 75% of pure linseed oil. It is of a semi-drying nature, but may be made to dry rapidly when mixed with manganese and lead linoleate driers. By compounding it under heat with tung oil and rosin, a substitute for linseed oil is produced, which some claim to be quite valuable.

TABLE I

Chemical Characteristics of Soya Bean Oil

Sample No. Specific gravity Acid No. Saponification
No. Iodine No. Per cent. of
foots 1 0.9233 1.87 188.4 127.8 3.81 2 0.9240 1.92 188.3 127.2 — 3 0.9231 1.90 187.8 131.7 — 4 0.9233 1.91 188.4 129.8 — 5 — — — 130.0 — 6 — — — 132.6 — 7 — — — 136.0 — Average 0.9234 1.90 188.2 130.7 —

TABLE II

Iodine Values of Linseed Oil

and Mixed Oils Sample No. Straight
linseed Soya
25 per cent.
Linseed
75 per cent. Soya
50 per cent.
Linseed
50 per cent. Soya
75 per cent.
Linseed
25 per cent. 1 190.3 175.2 160.7 140.4 2 189.5 175.9 161.7 140.8 3 188.0 175.4 160.3 139.0 Average 189.3 175.5 160.9 140.4

TABLE III

Soya Bean Oil and Lead Drier

Per cent.
PbO   0.05 0.10 0.30 0.50 0.70 1.00 1.30 1.60   ⎧ 1 day — 0.07 0.63 1.34 1.05 1.53 0.93 1.35   ⎪ 3 days — 0.07 3.52 4.31 2.75 4.86 4.82 4.12   ⎪ 5 days — 0.09 5.04 6.06 6.09 6.75 6.66 5.52 Per ct. gain ⎨ 12 days — — 6.88 7.54 7.43 7.76 7.32 6.47   ⎪ 15 days — — 8.84 8.93 8.59 8.81 8.44 7.46   ⎩ 20 days 0.05 0.20 9.02 9.08 8.90 9.03 8.65 7.83

Soya Bean Oil and Manganese Drier

Per cent. MnO2   0.01 0.05 0.15 0.26 0.30 Per ct. gain ⎧ 1 day — — 0.02 0.02 0.01 ⎨ 10 days — 5.06 6.48 6.10 5.97 ⎩ 20 days 0.05 9.07 8.80 6.78 6.51

Soya Bean Oil, Manganese and Lead Drier

Per cent. PbO   0.20 0.30 0.50 MnO2   0.05 0.15 0.25 Per ct. gain ⎧ 1 day 3.04 3.77 3.74 ⎨ 8 days 5.96 6.43 6.47 ⎩ 12 days 6.33 6.78 6.67

Tung Oil. There are grown in China and Japan many varieties of the “aleurites cordata,” popularly known as the tung tree. This tree bears great quantities of large sized nuts containing as high as 40% of an oil which yields itself in a viscous yellow form upon heating and crushing of the fruit. The raw oil, which chemically consists of the glycerides of oleic, oleo-margaric, and probably isomeric acids, is distinguished by its rapid drying properties. When spread in a thin layer it produces a hard film with an opaque frosted surface, often showing a tendency to wrinkle. Treated tung oil will dry to a clear, water-shedding, elastic film. This oil is made by heating the raw tung oil at a comparatively low temperature with other oils and a metallic drier

such as litharge.

The affinity of tung oil for rosin has resulted in the production of a series of moderate-priced varnishes most suitable for use in floor and deck paints or wherever great hardness is required. These varnishes are also finding application in the manufacture of concrete, steel, and flat wall paints; being especially suitable for the above purposes when compounded with kauri gum japan.

During the boiling of raw tung oil the temperature must not exceed much over 400 degrees Fahrenheit. Otherwise a peculiar “hamming” will take place, the whole mass becoming solid and of no further value as a varnish or paint vehicle. Some peculiar internal disturbance or rearrangement of the molecules is evidently effected by heat, and although the reaction is not clearly understood, it has been ascribed to auto-polymerization. Scott has stated that the phenomenon of gelatinization is due to the exposure of the surface of the oil to the air, and that boiling in vacuo obviates such results. The lusterless surface produced when tung oil varnishes are dried in vitiated air would tend to confirm the conclusion that the oil is very subject to atmospheric influences.

Lumbang Oil, which is obtained from a tropical species of Tung, is very similar in appearance and properties to Linseed Oil.

Constants of Tung Oils

  Sp. Gr. Iodine No. Saponifi-
cation No. Acid No. No. 1 .944 166 188 3.6 No. 2 .940 164 184 1.8

Menhaden Oil. Of all the marine-animal oils, such as seal, herring, sardine, whale, and menhaden, the latter is the most valuable. It is produced by steam digestion and pressure of the menhaden or “piogey” fish, which are caught in great quantities off the Atlantic Coast. Prompt cooking and treatment of the fish results in a light-colored oil having very little odor, the residue left in the presses being of great value as a fertilizer. Although several grades of oil termed crude, brown, light, etc., are produced, the most satisfactory for use in paint is that grade termed “light winter pressed.” This oil is of a pale straw color and has a high iodine number which is responsible for its rapid drying value. It contains less of the stearates that precipitate from crude oil, but sufficient to render its film water-shedding and elastic. The presence of too great a quantity of stearates is apt to result in a very soft film, and the use of hard driers, such as the metallic tungates, is therefore advisable with menhaden oil. When mixed with linseed oil paints the odor of menhaden oil is sometimes noticeable, but it disappears entirely after such paints are applied. Its use with linseed oil in technical paints exposed to the salty air of the Coast has given good results, often preventing “checking” and “chalking.”

The following constants were determined on samples of menhaden oil received in the writer’s laboratory:

  Sp. Gr. Iodine
Value Saponification
Number Acid
Number Light .927 175.8 187.9 7.55 Medium .925 178.7 187.6 6.19 Dark .927 178.0 187.3 7.19

Whale Oil. While ordinary whale oil is too dark and odorous to ever come into extensive use as a paint oil, it is probable that the refined oil will be utilized in the manufacture of certain technical paints. Whale oil is boiled from chopped whale blubber, the first trying being the lightest in color, while the later tryings, as well as the product made from bones, are of darker color and of very bad odor. Oil of mirbane is often used to mask this odor. The oil contains large quantities of stearin and palmitin, as well as wax-like constituents which are apt to be thrown out of solution in very cold weather, or when the oil is mixed with other oils. The refined oil, when ground with lead and zinc pigments and mixed with equal parts of linseed oil and treated tung oil, dries to an elastic and soft film. Experiments are being made to utilize whale oil in the linoleum

industry.

The analyses of samples of whale oil tested by the writer are as follows:

  Sp. Gr. Iodine
Value Saponification
Number Free Fatty
Acid Light Refined .924 148 190 .2 1.2 Dark Yellow .920 142 187   7.0 Dark Brown .910 140 184   18.0

Sunflower Oil. Sunflower oil is produced largely in Russia and Hungary, finding favor in those countries as an edible oil. The ripe seeds of the sunflower plant contain over 30% of oil which is very pale in color and of a pleasant smell. It has been found that sunflowers may be grown to advantage in dry parts of the United States, and if suitable yields are obtained from a few experimental acres now being cultivated, the industry may receive encouragement in this country. The oil should be well suited for varnish making, and although the iodine number is not very high, it dries quite rapidly.

Constants of Sunflower Oil

Sp. Gr. Iodine No. Saponifica-
tion No. Acid
No. .929 128 188 4

Cottonseed Oil. This oil is expressed from the seed of the cotton plant, varying in color according to the time of its pressing and degree of refinement. Being edible as well as highly suited for soap making, very little of it comes into the market as a paint oil. It contains large quantities of stearin and has a low iodine value, making it a slow drying oil. Some samples are extremely light in color and contain less mucilaginous matter and foots than is present in ordinary varieties.

Constants of Cottonseed Oil

Sp. Gr. Iodine No. Saponifica-
tion No. Acid
No. .922 106 190 2.4

Corn Oil. As a by-product in the manufacture of starch and alcoholic liquids, this material comes into the market having a golden yellow color, and an odor resembling fermented grain. It has a lower drying value than cottonseed oil, and its use in the paint industry will probably be limited to color grinding, where an oil with a semi-drying value is often desired. Like cottonseed oil, it belongs more properly to the soap oil class. It contains glycerides of linoleic and especially palmitic acid.

Analysis of Corn Oil

Sp. Gr. Iodine No. Saponification No. Acid No. .925 118 191 9.5

Rosin Oil. By the dry distillation of rosin, there is yielded a series of heavy dark oils consisting principally of hydrocarbons, resinous bodies, and free acid. These oils vary in their saponification number from 10 to 60, while their unsaponifiable value averages about 80. Of the grades termed first, second, third, and fourth run, the latter two are superior for use in paints, as a rule containing less free acid than the preliminary runs. Treatment with steam and alkali serve to neutralize the acid nature of the oils and to remove impurities. Refined oils are lighter in color and are often blown and bodied to fairly rapid drying products, especially when treated with manganese driers. Rosin oils are seldom used with lead pigments, on account of the presence of sulphur in the oils, which would result in darkening. Rosin oil paints work very smoothly, even when they are curdled, producing glossy surfaces. The rapid checking of rosin oil paints on wooden surfaces bars the use of this oil for such purposes.

Analyses of Rosin Oils

  Sp. Gr. Iodine
Value Saponifica-
tion No. Acid No. A .96 6 41 27 16.7 B .99   48 38 10.0

Hydrocarbon Oils. Several grades of neutral or mineral oils, varying somewhat in gravity, color, and quality, are produced as the last distillate in the refining of petroleum. These oils when mixed with drying oils and strong driers find application in the manufacture of some freight-car, barn, and other paints which sell at a low price. A small percentage of mineral oil is said to be valuable in structural steel paints, acting as a preventative of hard drying and thus keeping the film soft and elastic. Streaking and sweating is apt to ensue if any great quantity is used. Mineral oils have a characteristic bloom, showing a greenish fluorescence when examined by transmitted light. This bloom is due to the presence of some strongly fluorescent material which is shown up with intensity when mineral oils are exposed to ultraviolet rays such as emanate from an enclosed arc light. Outerbridge[1] first proposed this test for mineral oils, and he has worked out a “fluorescent scale,” by which very small percentages of hydrocarbon oils may be detected in other oils. Several types of so-called debloomed oil have been placed upon the market, and although such oils appear under ordinary light conditions to be free from bloom, they

fluoresce quite strongly when given the Outerbridge test.