6.6.20

Animalization of Vegetable Fabrics.

Scientific American 19, 8.5.1869

In the older theories of dyeing, it was held tha[t] the animal tissues of wool and silk absorbed and retained colors more readily than the vegetable tissues of cotton and linen, by virtue of some peculiar animal substance they contained. As a a consequence of this theory, attempts were made to communicate some animal principles to vegetable fabrics, with a view to improving their powers of receiving colors. The use of cow dung in dyeing madder goods; the use of sheep's dung and bullocks' blood, and urine in turkey-red dyeing, were explained, upon the supposition that they animalized the fabric in some way or other. The present view of animalization is, that it is not possible to animalize a fabric in any other way than by actually depositing upon it the animal matter in question, and that any increased facility for taking colors thus communicated, is effected by the animal matter itself held on the fabric, and not by any new property of the fabric itself. Thus, if a piece of calico is steeped in a solution of albumen, dried, and then steamed or plunged into boiling water, the albumen is fastened upon the cloth, and such cloth is then capable of receiving colors from picric acid, sulphate of indigo, magenta, archil, and other coloring matters, which previously had no affinity for the cloth. But it is impossible to look upon the albumen in any other light than as a kind of mordant acting as an intermediary between the color and the calico, differing, however, from ordinary mordants in some essential particulars. Beside albumen, the animal matters called casine and lactarine, possess similar properties, and have been tried on a large scale, but without any marked success, as mordants or bases for some of the colors, which are not attracted by the ordinary metallic mordants. The increased affinity for colors given to calico by oil, could not correctly, under any view, be called animalization, since the oils are all vegetable oils; but in fact there appears to be a considerable analogy between this case of mordanting and that by coagulable animal matters.

— Dictionary of Dyeing and Calico Printing.

A New Process For Determining the Comparative Value of White Lead

Scientific American 19, 8.5.1869

By Prof. C. F. Chandler

To determine the comparative value of different samples of white lead, it has generally been considered necessary to submit them to chemical analysis; an operation which can only be performed by a skillful chemist, and which, if carefully executed, requires much time, and involves, consequently, considerable expense.

It is therefore extremely important that a simple test should be devised, one so easy of execution that it may be applied by all persons interested in paints. Such a test was recently suggested to me by a person who has had many years of experience, in the white lead industry, and who desired me to submit his plan to a careful examination to test its reliability. This I have done, and the results are so satisfactory that I desire to place them before your readers, that those interested in the purchase and use of white lead may avail themselves of the test.


Properties of white lead.

The great value of white lead as a pigment depends upon its opacity, or as painters express it, its body," or "covering power." Pure white lead differs in opacity to a limited extent, according to the process by which it is made; that prepared by the Dutch method leaving the greatest covering power. The commercial varieties of white lead differ, however, to a far greater extent, owing to the extensive adulteration which is now practiced; sulphate of baryta, or barytes, a very heavy mineral, much cheaper than white lead, being the chief adulterant employed. The objection to the barytes is its transparency or want of body; it is not opaque, and consequently it does not cover well. A much larger quantity of the adulterated paint is required to produce the desired effect.

There is another objection to barytes, it has no affinity for the oil, and, consequently, when the adulterated paint is applied to surfaces which are exposed to the weather, as on the outside of houses, the oil quickly disappears, leaving the pigment loosely attached, and ready to be washed off by the rain.

Such paint rubs off readily upon our clothes when we come in contact with it.

White lead is a compound of carbonate and hydrated oxide of lead, which unites with the oil to some extent, producing a hard surface, which resists for a much longer tune the action of the elements. Oxide of zinc has a similar property.

From these statements the importance of a simple test of the quality of white lead will be readily seen.


The test.

The value of white lead depends upon its opacity; the more opaque it is, the more completely will it conceal a dark color. The test consists, therefore, in mixing a definite quantity of a dark pigment with a definite quantity of the white lead, spreading the mixture on a suitable surface, and noting the tint produced. In my experiments 100 grains of the pigment white lead, ground in oil, as it comes from the mill, were mixed with onehalf grain of Eddy's best lampblack, and four drops of boiled linseed oil. These substances were thoroughly incorporated, and then spread upon sheets of window glass, 6 by 12 inches, with a steel spatula. A few of my experiments will best illustrate the test. Pure carbonate of lead and pure sulphate of baryta, both ground in oil, were employed; onehalf grain of Eddy's dry lampblack, and four drops of boiled linseed oil, were mixed with—

 White lead. Barytes. Color produced.
1st 100 grains 0 grains light drab.
2d. 95 "5 " slightly darker drab.
3d. 90 " 10 " "
4th. 66 2/3 " 33 1/3 " "
5th. 50 " 50 " "
6th. 33 1/3 " 66 2/3"
7th. 0 " 100 " black.

The specimens were submitted to six different persons successively, and all agreed in pronouncing them as above recorded. Five per cent may therefore be considered the limit of the accuracy of this test.


Oxide of zinc

As oxide of zinc is often mixed with the white lead, experiments were made to determine the effect of this pigment upon the tints. The best American zinc white was employed. One-half grain of lampblack, and four drops of boiled linseed oil were mixed with—
 White lead. Oxide of zinc. Barytes.Gave color.
1st....33.33 33.33 33.33 lightblexish drab.
2d.....50 25 25 darker bluish drab.
3d.....50 12.50 37.50 still darker bluish drab.
4th... 50 6.25 43.75 "

The tint of the mixtures containing oxide of zinc was quite different from that obtained without the addition of this substance; while with white lead alone, or white lead and barytes, the color was a pure drab; the presence of six and a, quarter per cent of oxide of zinc was sufficient to communicate a very decided bluish tint. I think as little as two percent of oxide of zinc would make itself apparent in this way. This difference in tint makes it a little difficult to decide between two samples of adulterated white lead when one does, and the other does not contain oxide of zinc, as between tints so different in character, it is not easy to decide which is the darkest. In doubtful cases, however, this difficulty may be overcome by adding to both samples the same weighed quantity of oxide of zinc, say ten grains to each.

The colors communicated by the lampblack will then be of the same bluish tint, differing merely in intensity.

The only practical objection to this method of testing will arise from the difficulty of weighing half a grain of lampblack with sufficient exactness.

In my experiments, a chemical balance, which shows the thousandth part of a grain, was employed. The practical painter, however, will have no difficulty in applying this test with sufficient accuracy, if he will weigh out in ordinary scales, say 100 ounces (6 1/4 lbs.) of each sample to be compared, adding to each half an ounce of dry lampblack and an equal quantity to each sample of boiled linseed oil. After mixing the lead, black, and oil together, very thoroughly, spread each sample on glass, wood, or other smooth surface, as nearly alike as possible, when the difference in depth of color, produced by the black, will determine the comparative value or body of each sample.

The sample most discolored will have the least body, aired that least discolored the most body.

Another very simple test for determining the comparative value of any white paint ground in oil, was suggested by the same person — the correctness of which I have fully demonstrated — namely, weigh out, say 100 grains of each paint to be compared, add three drops of linseed oil to each, and spread them with a steel spatula on sheets of glass, 6 by 12 inches, as nearly as possible in the same manner. Place the samples thus prepared between yourself and the light, and you will have no difficulty in deciding which is most opaque. The sample which has obsured the light the most, or appears the darkest when held between yourself and the light, must have the greatest body or covering capacity.


Conclusion.

After having made a great number of experiments with these tests, I am satisfied that when they are applied with ordinary intelligence, they will not fail to determine the comparative value of the different grades of white pigments. would advise ,every person who makes use of these tests to begin by preparing a series of standard plates for comparison selecting samples of paint obtained from the most reliable makers.

Practical suggestions on tanning leather

Scientific American 19, 8.5.1869

By C. Gilpin.

(Continued from page 259)

Uniform temperature of liquors and disintegration of bark

It is generally conceded that the process of tanning is much more rapid during the summer months than through the colder seasons of the year. In other words, the tannin penetrates the hide much more readily during the months of May, June, July, August, and September, than during the other seven months of the year. Those who have given this subject any attention, have doubtless observed that during the summer months the liquor ranged from 70° to 80° Fahrenheit, and fell as low as 35° and 40° during the colder seasons in this climate, and perhaps lower in more northerly latitudes. What the difference in time required, to tan out a stock handled regularly in the liquors of the temperatures named, might be, I regret that I have no exact means of presenting to the trade, at this time, but shall endeavor to possess the information at no distant day, when I will make it public. One fact all are aware of, that it takes considerable less bark to maintain the liquors up to a certain degree of strength in cold than it does in warm weather; the tanning principle not being so rapidly absorbed by the hide, less bark is ground during the winter months.

I can well recollect when it was the custom among tanners to lay away their stock in very heavy layers during the month of October, after sending off all that was ready for market, and letting it lie until the frost was entirely out of the ground, when it would be drawn, and, as a consequence, was found to be but little advanced during that period.

It may be asked upon what principle can this be accounted for, and what is proposed as a remedy. The causes appear obvious, upon the wellsettled principle that all matter animate, as well as inanimate, is influenced by the elements, heat and cold, throughout all nature, to a greater or less degree, contracting and expanding the most solid metals, as well as the most delicate animal and vegetable formations; hence, when the liquor are below the expanding temperature, the hide contracts and the pores necessarily become more or less closed, and, when at that point, cause the hide to expand and the pores to open, just in proportion as the temperature is raised, until the whole mass may be disintegrated and a chemical change produced, which alters the entire organic structure of the material operated upon; thus it is clear that when the temperature of the liquors is allowed to fall below the expanding degree, the capillaries, by contraction, present an obstacle to the free passage of the tannin, and it cannot be taken up so rapidly; hence a much longer time is required to accomplish the object.

Having endeavored to define the cause, we will suggest a remedy, which will be to introduce, into every department of the yard, a regular temperature of liquor; and the facility with which the liquors can always be kept at a certain ten, perature, is the best reason why the manufacturer should lose no time in adopting it, particularly when, as a general thing, they have the facilities for supplying themselves with all the heat that may be necessary for this purpose; and, as a further auxiliary, all the operations of the tannery should be housed in good comfortable buildings, with steam pipes running through them, that would keep them at summer heat, or as warm as experience found necessary, then the junk through which all the liquor passes, should, by means of steam pipes, have sufficient heat thrown into it to insure the desired temperature throughout the entire yard at all times.

Thus, the liquor, passing from the vats to the junk, thence upon the leaches, with the entire establishment kept at a mild temperature, would, it is believed, accomplish all that is deemed necessary to overcome the loss sustained by the inaction produced by cold and freezing, weather upon the operations of tanning.

The expense of putting in pipes for the purpose of generating heat sufficient to warm the building, should be no obstacle, when we consider the cost as compared with the advantages gained. Mr. James Calley, of Pittsburgh, informed me that the cost of putting in twelve hundred feet of threequarter pipe, was two hundred dollars; this included all expenses; and from information received through wellinformed sources, it is believed that the whole cost of fitting up a firstclass tannery, with the necessary apparatus in the way of pipes, to accomplish our object, would not exceed twelve to fifteen hundred dollars, while the actual amount saved in time and labor in handling the stock, would, it is believed, fully equal one-half of the cost annually, to say nothing of making the workmen more comfortable, and thereby saving time that is always lost in warming feet and hands, in cold, frosty weather, which is the necessary consequence in all yards exposed to the frosts of winter, particularly in northern latitudes.

In communicating with the manufacturers upon the subject of having the bark thoroughly disintegrated before leaching, they pronounced, with one accord, that this was a great desideratum, if not the greatest want, in the operations of tanning. Now, that we have a system of leaching upon the upward hydraulic pressure, by which the liquid can be forced through any density that bark might acquire by being ground never so fine; believing, as most of them do, that under the present imperfect systems of preparing the bark, a considerable portion of the tanning principle is not, and cannot be extracted, under the methods of leaching in general use, without the application of steam and boiling, or very hot liquids, which, it has been repeatedly shown, are generators of impurities, that have an injurious influence upon the leather, what we want is a machine that will thoroughly separate the bark, and discharge it into the leach in the form of sawdust or shreds, allowing no part of it to escape without being brought to this condition. The best prepared bark that ever came under my notice, was prepared with stones arranged upon the plan of mill stones. It was thoroughly pulverized, or, perhaps, I might more properly say, ground into shreds. Under this method of grinding, no lumps or thick pieces could escape, as is the case now with the most approved mills in use. It would appear, from the past history of the world, in all ages and in all professions, that human nature has been averse to changing old methods for new ones, and the most useful as well as the most profitable improvements, have, too frequently, lingered longer in the murky and almost impenetrable atmosphere of prejudice, and those inveterate old fogies, custom and habit, than the advancement and interests of the great industrial pursuits of life would seem to demand. Yet, however much we dislike change in our systems of doing business, it is among the inevitable consequences, that necessity moves more individuals to adopt improvements than a desire to promote and encourage progress.