TABLE VI--LINSEED OIL AND MnO_{2} (MANGANESE) DRIER--TEST NO. 1
=========+=========+====+====+====+====+====+====+====+====+==== Per cent. 0.02 0.05 0.15 0.25 0.35 0.45 0.55 0.70 1.00 MnO_{2} ---------+---------+----+----+----+----+----+----+----+----+---- { 1 day 0.08 0.11 0.16 -- 3.21 3.46 3.27 3.01 2.76 { 2 days 0.16 5.88 4.48 -- 3.63 4.01 3.70 3.51 3.18 { 3 days 0.21 6.79 4.61 -- 3.83 4.31 -- 3.91 -- { 4 days -- -- 4.64 -- -- -- -- -- -- { 5 days 3.01 6.84 -- -- 4.13 4.68 4.19 3.91 3.99 { 6 days 8.00 -- 4.88 -- 4.37 -- 4.51 4.32 4.13 Per { 7 days 8.58 6.92 4.90 -- 4.48 -- 4.61 4.52 4.23 cent. { 8 days 9.06 -- 5.03 -- 4.55 5.23 4.77 4.62 4.44 gain { 9 days -- -- 5.12 -- 4.63 5.40 4.94 4.79 4.51 { 10 days 9.07 6.89 5.18 -- 4.81 5.47 -- 4.98 4.73 { 11 days 9.15 7.03 -- -- -- -- -- -- -- { 12 days -- -- -- -- 4.98 -- 5.45 5.33 5.22 { 13 days 9.22 7.17 -- -- 5.25 6.00 5.60 5.42 5.33 { 14 days 9.25 7.18 5.55 -- -- -- -- -- -- { 20 days -- 7.21 5.81 -- 5.84 6.70 5.94 5.84 5.77 =========+=========+====+====+====+====+====+====+====+====+====
TABLE VII--LINSEED OIL AND MnO_{2} (MANGANESE) DRIER--TEST NO. 2 (CHECK)
=========+=========+====+====+====+====+====+====+====+====+==== Per cent. 0.02 0.05 0.15 0.25 0.35 0.45 0.55 0.70 1.00 MnO_{2} ---------+---------+----+----+----+----+----+----+----+----+---- { 1 day -- 3.12 4.42 3.86 -- 3.19 2.98 3.27 2.56 { 2 days -- 6.15 4.73 -- -- 3.51 3.28 3.70 2.96 { 3 days 0.28 6.29 -- 4.12 3.72 -- 3.39 3.71 3.15 { 4 days 3.83 6.32 4.75 4.21 3.87 3.61 3.58 4.05 3.43 Per { 5 days 6.64 -- 4.84 4.23 3.94 3.73 3.65 4.21 3.56 cent. { 6 days 8.61 -- 4.87 -- 4.08 3.81 3.78 4.35 3.73 gain { 7 days 9.07 6.35 5.00 4.41 4.18 3.91 3.85 4.54 3.87 { 9 days 9.25 6.39 5.16 -- 4.44 4.11 4.21 4.63 4.26 { 11 days -- -- -- 4.63 4.59 4.36 4.31 5.07 4.46 { 16 days -- 6.43 5.30 4.91 4.83 4.72 4.71 5.40 4.87 =========+=========+====+====+====+====+====+====+====+====+====
TABLE VIII--LINSEED OIL AND PbO (LEAD) DRIER
=====+=====+=====+=====+=====+=====+======+======+=====+======+=====+====+==== Per cent. 0.00 0.05 0.10 0.30 0.50 0.70 1.00 1.30 1.60 1.30 1.60 PbO -----+-----+-----+-----+-----+-----+------+------+-----+------+-----+----+---- { 1 0.042 0.049 0.092 0.058 0.066 0.062 0.062 0.079 0.039 0.14 0.72 {day { 2 0.098 0.104 0.153 0.116 0.158 -- 0.194 4.83 4.79 5.27 6.11 {days { 3 0.128 0.159 0.170 0.137 0.279 0.185 7.11 8.60 5.35 7.89 8.28 {days { 4 0.164 0.214 0.206 0.178 -- 4.07 7.39 9.55 8.53 7.93 8.68 {days { 5 0.176 -- 0.306 -- 0.340 7.60 7.47 9.87 8.78 8.18 -- {days Per { 6 0.188 0.231 -- 0.243 0.472 9.36 7.64 10.01 9.00 8.24 9.09 cent. {days gain { 7 0.206 0.251 -- 0.253 1.080 10.06 -- 10.14 -- -- -- {days { 8 0.212 0.253 -- 0.280 4.80 10.38 7.70 10.22 9.05 -- -- {days { 9 0.226 0.291 0.306 0.331 7.36 10.41 7.73 10.23 9.07 -- -- {days {13 0.327 0.428 0.510 0.674 11.01 10.67 7.91 10.48 9.29 8.62 -- {days {15 0.466 0.455 0.650 2.41 11.05 -- 7.92 10.50 9.30 -- -- {days {20 0.521 1.08 1.78 8.76 11.25 10.67 7.98 10.52 9.36 -- -- {days =====+=====+=====+=====+=====+=====+======+======+=====+======+=====+====+====
TABLE IX--LINSEED OIL AND PbO (LEAD) AND MnO_{2} (MANGANESE)--COMBINATION DRIER
=================+========+=====+=====+======+======+====+=====+==== Per cent. PbO 0.1 0.3 0.5 0.7 0.9 1.1 1.4 -----------------+--------+-----+-----+------+------+----+-----+---- Per cent. MnO_{2} .005 .015 0.025 0.35 0.45 0.55 0.7 -----------------+--------+-----+-----+------+------+----+-----+---- { 1 day 0.026 0.061 0.055 0.022 0.16 0.11 3.06 { 2 days 0.094 0.087 0.143 0.16 5.21 6.28 3.37 { 3 days 0.118 -- 0.17 4.23 7.63 8.31 3.74 { 4 days -- 0.11 0.23 7.36 8.87 9.20 4.02 { 5 days 0.120 0.12 0.29 9.04 9.13 9.37 4.17 Per cent. gain { 6 days 0.17 0.13 1.44 9.88 9.26 9.51 4.34 { 7 days 0.21 0.18 4.65 10.11 9.28 -- 4.45 {11 days 0.30 0.26 10.03 10.35 9.61 9.85 5.11 {12 days -- -- -- 10.45 9.66 -- -- {13 days 0.35 0.54 10.37 10.51 9.67 10.03 5.33 {18 days 0.49 3.43 10.38 10.62 9.68 -- 5.73 =================+========+=====+=====+======+======+====+=====+====
In the same way with lead driers, excessive amounts of lead oxide seem to have no beneficial effects on the drying of an oil, and when the percentage which seems to be the most beneficial, namely 0.5% lead oxide, is exceeded, the film is apt to become brittle.
Oils containing lead oxide driers are less influenced in their drying tendencies by conditions of moisture in the atmosphere than oils containing manganese, but frequently, however, the former dry much better in a dry atmosphere. As a general rule, varnishes rich in manganese dry more quickly in a dry atmosphere, while those containing small quantities dry more quickly in a damp atmosphere.
=Volatile Products Formed.= It was furthermore noticed in these tests that sulphuric acid, placed in dishes on the bottom of the large box in which the samples of oil were drying, was discolored and turned brown after several days, showing that the acid had taken up some material of a volatile nature that was a product of the oxidation.
Another curious feature of these tests was the development of a peculiar aromatic odor which was given off by the oils upon drying in dry air.
When the oils were dried in moist air, a rank odor resembling propionic acid was observed, and this led the observer to believe that a reaction was effected by the absorbed oxygen, that caused the glycerin combined with the linoleic acid as linolein to split up into evil-smelling compounds. It has been suggested that the oxygen first attacks the glycerin, transforming it into carbonic acid, water, and other volatile compounds, which are eliminated before the oil is dried to linoxyn.
Toch,[3] however, has shown that the drying of linseed oil gives off only very small percentages of carbon dioxide. Mulder has observed that in the process of linseed oil being oxidized, glycerin is set free, which becomes oxidized to formic, acetic, and other acids, while the acid radicals are converted by oxygen into the anhydrides, from which they pass by further oxidation into linoxyn.
[3] Toch: The Chem. and Tech. of Mixed Paints, p. 89. D. Van Vostand Co., N. Y.
=Auto-Oxidation of Oil.= The theory of auto-oxidation of linseed oil has been very ably treated by Blackler, whose experiments indicated that during the drying process the slow absorption of oxygen was, at a critical period, followed by a rapid absorption, which he attributes to the presence of peroxides. The materials produced by this peroxide formation may act as catalyzers and accelerate the formation of more peroxide. Lead and manganese oxides may also be oxidized to peroxides by the action of oxygen, and in this event might act as very active catalyzing agents or carriers of oxygen. Blackler's statement, that the presence of driers do not increase, but have a tendency to decrease the initial velocity of oxygen absorption, has been confirmed by these experiments, but it has been noticed throughout the tests that the driers have an accelerative action at a later period.
=Effect of Metals on Drying of Oils.= Some most interesting results were secured by dipping extremely fine copper gauze into linseed oil, and then suspending the gauze in the air. The adhesion of the oil to the copper caused the formation of films between the network, and remarkable drying action was observed. The copper or any superficial coating of copper oxide which may have been present on the metal, undoubtedly affected the result to some extent. It has been found that metallic lead is even more efficient than copper in this respect, but this may be due to the action of free acid in the linseed oil, forming lead linoleates, products that greatly accelerate drying. Another interesting experiment was made by immersing pieces of gauze cloth in linseed oil. After the excess oil had been removed, by pressing, the cloth was again weighed to determine the amount of oil used for the experiment. The increase in oxygen absorption in this case was very rapid, and the result obtained confirmed the results in the other experiments.
In order to secure a more evenly distributed state of the oil, tests were conducted by saturating pieces of stiff blotting papers, and, after exposure, weighing as usual.
=Influence of Light.= The influence of light on the drying of oils is unquestionably a potent one. The practical painter knows that a certain varnish will dry quicker when exposed to the light than when in the dark.
Chevreul was one of the first pioneers in this field of research to observe the effects of colored lights on drying, and he claimed that oil exposed under white glass dried more rapidly than when exposed under red glass, which eliminates all light of short wave lengths.
Genthe obtained interesting results in the drying of oil submitted to the effect of the mercury lamp. Oxidation without driers was effected probably through the formation of peroxides. In commenting on this subject, Blackler[4] gives a description of the use of the Uveol Lamp, which is similar to the mercury lamp, but has, instead of a glass casing which cuts off the valuable rays, a fused-quartz casing which allows their passage.
[4] M. B. Blackler: "The Use and Abuse of Driers," P. and V. Society, London, Sept. 9, 1909.
=Driers in Boiled Oil.= In the boiling of linseed oil, by certain processes the oil is heated to 250 F. and manganese resinate is incorporated therein. It goes into solution quite rapidly. In other processes the oil is heated to 400 F. or over, and manganese as an oxide is boiled into the oil. Although it is unsafe to say that a small percentage of rosin, such as would be introduced by the use of resinate driers, is not harmful, yet it appears that this process should give a good oil, inasmuch as it has been found that no matter whether the manganese is added to the oil, as a resinate, borate or oxide, practically the same drying effect is noticed in every case where the percentage of manganese is the same. It is the opinion of some, however, that the resinate driers are not as well suited for durability as oxide driers. However, if a boiled oil is found to contain on analysis a small percentage of rosin less than 0.5% or a percentage only sufficient to combine with the metal present, it should not be suspected of adulteration. Practical tests should be made with such oil along with an oil made with an oxide drier, before pronouncing on their relative values. Inasmuch as the addition of certain driers to linseed oil lessens the durability of the film, it is more practical to use the smallest amount of drier that will serve the purpose desired, that is, set the oil up to a hard condition which will not take dust and which will stand abrasion.
The results of this investigation would indicate that when lead or manganese linoleates are used, the most efficient drying is shown with 0.5% lead or with 0.02% manganese, or with a combination of 0.5% lead and 0.02% manganese.
Until more definite results have been obtained with the _tungates_, which will probably prove of exceptional interest as driers, the above driers will probably be used to the greatest extent.
=Co-operative Drying Tests.= A series of important drying tests made by members of a special committee[5] appointed by the American Society for Testing Materials, of which the writer was chairman, is herewith shown:
[5] Sub-Committee C of Committee D-1, on Testing Paint Vehicles. Proc.
Amer. Soc. for Test. Mater., 1911.
"At the January meeting of Committee D-1, a sub-committee consisting of the following members was appointed to investigate paint vehicles:
G. B. Heckel, Glenn H. Pickard, Allen Rogers, A. H. Sabin, H. A. Gardner, _Chairman_.
"At a subsequent meeting of the sub-committee it was determined to start the investigations with a series of tests on certain drying, semi-drying, and non-drying oils, determining their drying values, rate of oxygen absorption, etc., when spread out in thin films. A quantity of the following oils was selected for the tests and subsequently secured from sources known to be reliable:
Lead and manganese linoleate drier.[6]
Lithographic linseed oil.
Boiled linseed oil (resinate type).
Boiled linseed oil (linoleate type).
Blown linseed oil (containing drier while being blown).
Heavy mineral oil.
Rosin oil.
Soya bean oil.
Corn oil.
Cottonseed oil.
Sunflower oil.
Menhaden oil.
Chinese wood oil, raw.
Chinese wood oil, treated.
Perilla oil.[7]
Lumbang oil.[7]
Dry rosin 20%, boiled in 80% linseed oil.
[6] The drier used, upon analysis, showed the presence of 4.36% PbO and 2.51% MnO_{2}.
[7] The lumbang and perilla oils were imported and arrived subsequent to the starting of the tests. They were therefore not included in the tests.
"Four-ounce sample bottles of each oil were sent to the Committee members, with the request to proceed with the tests along the lines agreed upon at the Committee meeting. The instructions for making these tests are outlined as follows:
(_a_) A series of small glass plates, approximately 5 by 7 ins., are to be prepared by each member of the Committee. These plates are to be thoroughly cleaned and carefully numbered and weighed upon a chemical balance. The oils to be used for the tests are to be numbered corresponding to the plates. A test of each oil is to be made by painting it upon the surface of a glass plate with a camel's-hair brush, subsequently weighing the plate and the oil. These tests are to be exposed under constant conditions of temperature, if possible, for three weeks' time, making weighings of each plate every day for six days and then every other day for twelve days.
(_b_) Another series of tests shall be made, in which 80% of raw linseed oil is to be combined with each of the above oils named. Previous to making any of the tests, _there should be added to each oil, or to each combination, 5% of a drier containing lead and manganese_. The drier to be used is of the standard grade submitted, together with the oil samples. The results of the tests are to be charted and submitted at the end of the tests, so that they may be compared with the results obtained by each member of the Committee.
(_c_) If possible, the oils and mixture of oils used in the above tests are to be ground with pure silica and painted out upon sized paper, three-coat work, the films to be stripped and tested for strength upon a paint filmometer, at two periods two months apart."
The drying of oils to a firm surface when spread in a thin layer is accompanied by an increase in weight, due to the absorption of oxygen.
The percentage of oxygen absorbed often affords a criterion of the drying of the oil under examination, and this factor, together with data regarding the appearance of the oil film, should be taken into consideration when judging the value of an oil or oil mixture.
Conditions of light, air, temperature, etc., often cause great variations in the drying of oils and the percentage of oxygen absorbed, as shown by the results obtained in the following tests. Although it was impossible in these tests to have the conditions under which each experimenter worked parallel in nature, the tests afford nevertheless considerable information for guiding future work of a similar nature.
An examination of the results obtained showed generally that the greatest increase in weight occurred during the period in which the oil dried up to a firm film. This occurred in most cases within 48 hours.
After this period a slight increase in weight was often noticed, and then a more or less steady decline, varying with the oil examined. Had the oil tests been continued for a greater length of time, a much greater loss might have been observed.
It was impossible to include in the tests the oil-silica film work, on account of lack of time. It is believed, however, that these tests should be conducted, as they would throw much light on the elasticity and strength given to paint films by various oils.
TABLE I.--(_a_) BOILED LINSEED OIL (RESINATE TYPE) 100 PER CENT.