Association of Master Painters and Decorators and the results obtained were published generally in the paint journals. Undoubtedly, these tests were conducted conscientiously and the conclusions reported give honest opinions about the results obtained. We feel, however, compelled to question these results for several reasons which appear to me to be very important. In the first place, single boards only were painted with each paint and exposed. At least three boards should have been painted and exposed alongside of each other, and the board which showed results about the average of the three should have been selected for comparison with other paints similarly selected. Very frequently, it will be found that two boards painted apparently in the same manner and with the same paint, will show differences in results due to differences in the boards themselves. In the second place, the formulæ on which the paints were mixed are not stated with sufficient detail. In the third place, there is no information given as to the spreading rate at which the respective paints were applied. Considering any two of the boards, the paint on one board may have been twice as thick as on the other, for all we know to the contrary. We have very little doubt that the thicker the paint film, the greater its durability. This emphasizes the importance of having painting tests conducted under the supervision of the engineer or chemist. The ordinary master painter is, we believe, thoroughly competent to interpret results and to conduct field tests on full-sized structures, but when it comes to preparing boards for exposure, special training is required, such as the chemist or engineer only can be said to have.

To conclude, no matter what the painting test may be, whether it be of colored paints or white paints, whether it be with homogeneous or mixed pigments, whether it be for covering power or durability, the essential features that we should insist upon are, that the formula of the paint should be stated fully; that the thickness of the film-or what is the same thing, the rate at which the paint is spread-should also be stated. These two requisites of proper painting tests should also be demanded in all tests for the permeability of paint films or their permanency, no matter how these tests may be applied. If we wish to compare two paint films for their permeability by the dextrine test, we should know, to start with, that these two films have approximately the same

thickness. It is a safe assumption that the thicker the paint film, the less its permeability. If we desire to compare two paint films for their permanency, we should know that these two paint films are of the same thickness, as the elasticity and general life of the film are proportionate to its power of resistance to oxidizing influences, and the thicker the film, the more permanent are its inner parts.

Mr. Toch.

THE PRACTICABILITY OF ESTABLISHING STAND

ARD SPECIFICATIONS FOR PRESERVATIVE

COATINGS FOR STEEL.

TOPICAL DISCUSSION.

MAXIMILIAN TOCH.-It gratifies me very much to be invited to give my opinion on the Practicability of Establishing Standard Specifications for Preservative Coatings for Steel, but in treating this subject, I find it exceptionally difficult to know where to begin, and I should say, the subject is too vast a one to be taken up in a general way.

I call to mind the preservation of the steel in the supers ructure of our large buildings which must be treated in a certain way; again, the preservation of the grillage beams which form the founda tion of some of such structures. I have in view the requirements for the preservation of the structural steel in bridges against the action of the natural elements and against the action of electricity; again, the preservative coating for the interior of a structure in which a weak acid is evaporated continually at warm temperatures. These are merely suggestions of the various kinds of steel structures. that have to be coated, some permanently and some temporarily, and I am sure you will agree with me that in each case a specific treatment is necessary.

A paint that will answer for the preservation of a hand-rail subjected to electrolytic action will manifestly not answer for steel that is to be immersed in water impregnated with benzol. For purposes of preservation, a coal car and a steel stack should not be treated in an identical manner, and similarly an elevated structure should be painted totally differently from the steel structure of a subway. A paint that may answer its purpose perfectly when subjected only to a variation in temperature of 40° F. and never subjected to brilliant light, may obviously fail when exposed to the sunlight and subjected to a variation of temperature of 130° F.

I am, therefore, of the opinion that each particular case requires appropriate treatment. I know of a building in which an acid-proof paint was necessary for the steel supports on the ground floor, and where a good linseed oil paint met all requirements on

the upper floors. It has also to be considered whether a beam be Mr. Toch. permanently imbedded in concrete or whether it can be looked after and maintained. A bridge which is partially subjected to fumes of locomotive gases must be treated differently from a bridge. which crosses a stream and carries, perhaps, very light traffic. Pipes subjected to the action of brine cannot be treated in a manner similar to pipes which carry live steam.

I am quite sure that we have not sufficiently studied the action of electricity on paint and steel, and it is necessary for us before long to take this matter up very seriously.

As far as pigments are concerned, my personal opinion is that no single pigment is a panacea for all evils, but that a mixture of various pigments is frequently far superior.

Red lead if neutralized with a very light pigment like carbon black or graphite, makes a paint superior to either one or he other alone. Certain forms of ferric oxide, those of high specific gravity and neutral conditions make most excellent structural paints for severe exposure, particularly when they are lightened in bulk with some other inert pigment. The ferric oxides have the great advantage of being unaffected by normal conditions. It frequently happens that red lead in the presence of sulphur vapor forms a lead sulphide, which, owing to its atomic increase, peels from the surface to which it is applied. It is not generally known but it is a fact that some of the ferric oxides are perfectly stable, are not affected by gases, and cannot change their composition; and that some of the pure red oxides of the composition Fe,O, are used by rubber manufacturers for making red rubber, and when vulcanized in the presence of sulphur at a temperature of over 300° F., these oxides remain unchanged.

3

Much has been said in favor of hydro-carbon paints, and while I have a high opinion of these paints, I feel that an exact knowledge of the nature and conditions of the poly-methylenes is necessary before a uniformly successful paint can be made of these hydrocarbons. Sunlight is the great destroyer not only of poly-methylenes, but of many of the varnish and oil paints.

I made a series of tests extending over a year, which were very carefully carried out, and demonstrated to my own satisfaction that the asphaltum or pitches which were of the poly-methylene series give up hydrogen under the action of sunlight, thereby

Mr. Toch.

Mr. de Wyrall.

liberating the carbon. It is not my intention to go into this subject further than I have, for the reason that it is too scientific, but a fundamental study of the composition of raw materials of this nature is essential to the manufacture of hydro-carbon paints, because where alkaline and acid conditions prevail, it is necessary to use the poly-methylenes and the paraffines as bases. The pigment paints have serious disadvantages as primers against electrolysis.

MR. CYRIL DE WYRALL.-During the last three years I made a number of comparison tests under conditions differing from the ordinary, that is, in a place where we had everything we should not have had, and did not want, in the way of gases, condensation, humidity, etc. My remarks will be confined to actual tests, not laboratory tests, but service tests during the last three years, of preservative coatings for steel in the New York Rapid Transit Subway.

I should like to say a word in regard to the slow and quickdrying paints we have tried. Three of the best paints we tried dried free from dust in about ten minutes. The only three that have stood the different tests during that length of time are the paints that dried free from dust in ten minutes. You could lean against them without any danger in from thirty to forty minutes. The original specifications called for a coat of red lead and boiled linseed oil, weighing, ready-mixed, 22 lbs. per gallon. After the steel was erected it was properly cleaned and given another coat of red lead, and this was covered with a coat of white lead and boiled linseed oil. In about six cases out of ten, the columns had to be sand-blasted before they were erected. As soon as sand-blasted, coated and placed in position, after the work was finished, or as it progressed, we cleaned them thoroughly, getting off all the scale that might be left on, and coated them again with red lead and then with white lead. The materials used were chemically pure, cach batch being tested, yet, notwithstanding all this, on Section 7 there were evidences of corrosion in eight months after the final coat was applied. It formed in little blisters like pin-heads all over the face of the columns. I watched them closely to see what would happen and little specks of rust came through at these points. You could wipe it off; the paint was perfectly good and there was no visible abrasion. These small spots,