Paint Technology and Tests Part 20

WAs.h.i.+NGTON PAINT TESTS

The new vehicle test fence at Was.h.i.+ngton is fully described in the writer's paper[31] as presented before the American Society for Testing Materials, as follows:

[31] The Practical Testing of Drying and Semi-Drying Paint Oils, by Henry A. Gardner. Paper presented at Fourteenth Annual Meeting, Amer. Soc. for Test. Mater., Atlantic City, N.J., June, 1911.

"The high price attained by linseed oil during the past two years of over a dollar a gallon, together with the unusual scarcity of this valuable oil, has led many investigators into the field of research, with a view of discovering some mixture of other oils to partly replace linseed oil. Many valuable contributions to oil technology have resulted, but the makers and users of paints have wisely demanded specific and authoritative information as to the practical value of proposed mixtures before adopting them. The Inst.i.tute of Industrial Research, at the request of the Paint Manufacturers' a.s.sociation of the United States, has recently started a series of practical paint vehicle tests designed to decide the question at issue.

"Forty-eight white-pine panels have been placed upon a test frame on the grounds of the new laboratory building of the Inst.i.tute, at Was.h.i.+ngton, D. C. They are painted with a standard white pigment formula reduced with a different oil formula for every panel. White-pine panels were selected for the test on account of the good painting surface which this type of lumber presents; the grade selected was free from knots or pitch pockets--defects which often ruin a paint test. Each panel was constructed of four tongued-and-grooved planed boards, 22 inches long, 1 inch thick, and 9 inches wide. The boards were leaded together and capped at the sides with weather strips, making the finished panels about 2 feet wide and 3 feet high. The fence upon which the panels were placed was constructed of 4-inch squared yellow pine with open framework, allowing the panels a resting place upon which they were finally secured with sherardized screws.

"Before erecting the panels, they were carefully painted in a paint laboratory especially fitted out for the tests. The work was done during the months of April and May, the temperature averaging from 60 degrees to 90 degrees Fahrenheit. This precaution was taken in order that the paint in each case might become thoroughly dry and hard before exposure, so that there would be no acc.u.mulation of dust or effect from exposure during the drying period. The actual painting of each panel was done personally by Mr. Charles Macnichol, master painter, of Was.h.i.+ngton, D.

C., who has had a wide experience in the practical application and testing of paints.

[Ill.u.s.tration: View of Panels on Was.h.i.+ngton Test Fence]

"The viscous nature of several of the oils tested precluded the possibility of grinding each oil formula with the white pigment base selected; great heating of the paint mills and a paste of insufficient fineness was the result of an early attempt at this method. It was decided, therefore, to grind the standard pigment formula to a thick paste in the minimum amount of raw linseed oil. Subsequently a weighed amount of the white pigment base was thinned with the oil formula to be tested, to a standard viscosity, judged by the experienced master painter in charge of the practical application of the formulas as sufficiently heavy for third-coat work. When making the reductions with oil mixtures, an allowance was made for the amount of linseed oil already contained in the ground white pigment base.

"During the application of the first coat an equal amount of turpentine was added to each formula, in the proportion of one-half pint to a gallon of paint; in the application of the second coat there was added to each formula a like amount of an equal mixture of turpentine and the oil formula under test. The third coat was applied without the addition of thinners of any kind.

"It is well known that the time of drying and the condition of the dried film of any oil or mixture of drying or semi-drying oils will vary widely. It is for the purpose of causing oils to set up to a hard film in a short time that metallic driers in the form of salts of manganese and lead, soluble in oil, are added to a paint. Some oils require a large amount of drier, while others require only a very small amount.

Those which require a large amount are apt, upon exposure, to be burned up by the drier, resulting in the formation of a powdered and disintegrated film. To add various types of drier or even differing amounts of a drier to the oils under test, seemed very unfair from every standpoint, and it was therefore decided to eliminate the drier question entirely, so as not to vitiate the results by bringing in a factor of this nature. The plan of omitting driers proved successful in the Atlantic City steel-panel paint tests, erected three years ago by the writer under the supervision of Committee A-5 of this Society.

"The systematic methods which are necessary when making paint tests were carefully followed. A standard weighed amount of white pigment paste was placed in a clean paint cup and thinned to the proper consistency with a weighed amount of the oil under test. Proper reductions were made, as before stated. Weighings of the paint, cup, and brush were made before and after application to the panel, in order to determine the quant.i.ty of paint used and the spreading power. A period of fifteen days was allowed between the application of successive coats, in order to give each formula sufficient time to dry thoroughly. Although several of the formulas remained tacky for over a week, all dried thoroughly in the time allotted. (Oils which when used alone have slow drying properties, have been found to yield good firm films when used with drying pigments such as lead and zinc.) The backs and edges of each panel were painted with two coats of the paint used on the face of the panel, so as to prevent the admission of moisture. After erection, the panels were numbered with aluminum figures pressed into the surface. Frequent inspections will be made, and at the proper time reports will be issued giving the results of the tests.

"During the painting of the panels considerable interesting data were collected, of which the following is a brief resume:

"The hiding power of a paint is one of its most important requisites. It was found in the tests that some oils had the effect of lessening, while others had the effect of increasing the hiding power of the standard pigment formula. This may be due in part to the varying refractive indices of the oils used, as well as to the difference in the quant.i.ty of oil required in each test. Some oils were very viscous, while others were very light.

"The stiff working of heavy-bodied, blown, or heat-oxidized oils, produced films which in some cases gave a very glossy surface, even on the priming coat. Some of these resembled varnished work when finished.

It will be of importance to watch these tests carefully for any signs of early breakdown, which might come from too thick a film. The treated Chinese wood oil paints worked rather stiff but produced very smooth films. The rosin oil paints became slightly lumpy on standing, but worked out to a smooth finish somewhat yellowish in color. The marine animal oils, especially the menhaden oil mixtures, dried to a film slightly flatter than straight linseed oil. Any odor which was present in the paints made from the animal oils seemed to disappear a few hours after application. The cotton seed and corn oil mixtures made the slowest drying paints, but at the end of the second week of the drying period they set up rapidly to firm films. Soya bean and perilla oils behaved like straight linseed oil, the former being a little slower and the latter slightly more rapid in drying properties. The perilla oil was made from one of the first importations into this country, and was dark in appearance. It made, however, a very easy-working and hard-drying paint.

"The oils used in the tests were obtained from reliable sources. After they were received, they were carefully a.n.a.lyzed. The results of the a.n.a.lyses appear in Table 1.

TABLE 1. a.n.a.lYSES OF OILS USED IN THE VEHICLE TESTS

===================================+=========+=========+========+======== |Specific |Saponifi-|Iodine | Acid |Gravity | cation |Number |Number | | Number | | -----------------------------------+---------+---------+--------+-------- Raw linseed oil |0.931 | 188 | 186 | 2.0 Boiled linseed oil (linoleate type)|0.941 | 187 | 172 | 2.7 Boiled linseed oil (resinate type) |0.930 | 186 | 176 | 2.2 Blown linseed oil |0.968 | 189 | 133 | 2.8 Lithographic linseed oil |0.970 | 199 | 102 | 2.7 Soya bean oil |0.924 | 189 | 129 | 2.3 Menhaden oil |0.932 | 187 | 158 | 3.9 Perilla oil |0.94 | 188 | 180 | 2.0 Chinese wood oil (raw) |0.944 | 183 | 166 | 3.8 Chinese wood oil (treated)[32] |0.898[32]| 128[32]| 104[32]| 6.8[32]

Corn oil |0.925 | 191 | 118 | 9.5 Cottonseed oil |0.921 | 193 | 105 | 3.6 Rosin oil |0.966 | 27 | 41 |16.7 Whale oil |0.924 | 191 | 148 | -- Neutral petroleum oil[33] |0.916 | 6 | 12 | -- ===================================+=========+=========+========+========

[32] Low constants due to presence of over 40% of volatile matter, largely petroleum spirits.

[33] This oil contained over 20% of petroleum spirits.

"The pigment formula selected for the tests had the following composition:

Basic carbonate-white lead 20% Sublimed white lead 30% Zinc oxide 35% Magnesium silicate 10% Barytes 5%

100 lbs. of pigment base ground to a stiff paste in 16 lbs. of linseed oil.

"While this pigment formula was not selected as being superior to certain other formulas, it is of a type that has given very fair service in paint tests throughout the country, and will no doubt serve admirably for the purpose designed in these tests.

"The vehicle formulas in the finished paints are as follows:

No. 1 Raw linseed oil 100%

No. 2[34]

Soya bean oil 100%

[34] Dry pigment formula in soya bean oil.

No. 3[35]

Menhaden oil 100%

[35] Dry pigment formula in menhaden oil.

No. 4 Raw linseed oil 25% Boiled linseed oil (resinate) 75%

No. 5 Raw linseed oil 25% Boiled linseed oil (linoleate) 75%

No. 6 Raw linseed oil 50% Boiled linseed oil (resinate) 50%

No. 7 Raw linseed oil 50% Boiled linseed oil (linoleate) 50%

No. 8 Raw linseed oil 50% Blown linseed oil 50%

No. 9 Raw linseed oil 50% Litho. linseed oil 50%

No. 10 Raw linseed oil 50% Soya bean oil 50%

No. 11 Raw linseed oil 50% Menhaden oil 50%

No. 12 Raw linseed oil 50% Perilla oil 50%

No. 13 Raw linseed oil 50% Treated wood oil 50%

No. 14 Raw linseed oil 50% Corn oil 50%

No. 15 Raw linseed oil 50% Cottonseed oil 50%

No. 16 Raw linseed oil 50% Rosin oil 50%

No. 17 Raw linseed oil 50% Whale oil 50%

No. 18 Raw linseed oil 75% Soya bean oil 25%

No. 19 Raw linseed oil 75% Menhaden oil 25%

No. 20 Raw linseed oil 75% Perilla oil 25%