THE PRESERVATION OF TIMBER.2

THE PRESERVATION OF TIMBER.²

REPORT OF THE COMMITTEE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS ON THE PRESERVATION OF TIMBER, PRESENTED AND ACCEPTED AT THE ANNUAL CONVENTION, JUNE 25, 1885.

BOUCHERIE, OR SULPHATE OF COPPER.

The name of Dr. Boucherie is generally applied to the process, which he invented and extensively applied, of preparing wood by forcing a solution longitudinally through the pores of the wood by means of hydraulic pressure. As, however, he also patented the use of sulphate of copper, and his name became attached to the use of that antiseptic, it will be convenient here to classify experiments made with that substance under this head.

Dr. Boucherie was a distinguished French chemist, who between 1836 and 1846 made many elaborate researches and experiments upon the preservation of timber. He tried many substances, and at first recommended the use of pyrolignite of iron, but subsequently used sulphate of copper, which he considered more effective.

His first experiments were conducted by vital suction, that is, by tapping the living tree, and allowing the ascending sap to carry up a preserving solution. This was not found to give uniform or satisfactory results, and Dr. Boucherie then invented the process which bears his name. This was practiced either by applying a cap to the end of a freshly cut log, through which the solution was allowed to flow by pressure, or by sawing a log nearly through in the middle, raising it at the center slightly, so as to open the joint, placing a strip of tarred rope or a rubber band just inside the periphery of the cut log, and letting it spring back, so as to form a tight joint by pressing upon the rope or band. An auger hole bored diagonally into the cavity so formed then served to admit the solution under pressure.

This process, applied with a solution of about one pound of sulphate of copper to one hundred pounds of water, has been extensively applied in France for many years, with satisfactory results. It was found, however, that to be successful it must be applied to freshly cut trees in the log only, and that this involved so much delay, moving about, waste, and annoyance, that it has now been abandoned. These difficulties would be still greater in this country, and in the Northern States the process could not be applied at all during the winter (or season for cutting down trees), as the solution would freeze.

On this page is a list of the experiments which your committee have been able to learn about, as having been made with sulphate of copper in this country.

RECORD OF AMERICAN EXPERIMENTS.

SULPHATE OF COPPER, OR BOUCHERIE.

COMMENTS ON SULPHATE OF COPPER EXPERIMENTS.

The first experiment was carried out by Mr. W.W. Evans, on the Southern Railway of Chili, in 1857, and he informs your committee that in 1860, when he left that country, the ties were still good and in serviceable condition.

We give herewith, in Appendix No. 16, an interesting letter from Mr. E. Pontzen to Mr. Evans, on the subject of the Boucherie process.

Experiments Nos. 2 to 16, inclusive, were all tried with various modifications of the sulphate of copper process as introduced by Mr. W. Thilmany in this country. They date back to 1870 (experiment No. 2), when Mr. Thilmany was working and recommending the methods of vital suction and of the Boucherie hydraulic pressure system. After describing the foreign methods of injection with sulphate of copper, he states in his first pamphlet (1870): "This process resulted very satisfactorily, but it was found that the sulphate of copper became very much diluted by the sap, and when the same liquid was used several times, the decaying substance of the sap, viz., the albumen, was reintroduced into the wood, and left it nearly in its primitive condition."

He accordingly proposed a double injection, first by muriate of barytes, and, secondly, by sulphate of copper, forced through by the Boucherie process, and it is presumed that the ties of 1870, in experiment No. 2, which showed favorable results when examined in 1875, were prepared by that process.

Subsequently Mr. Thilmany changed his mode of application to the Bethell process of injecting solutions under pressure in closed cylinders, and probably the paving blocks for experiment No. 3 were prepared in that way. The chemical examination of them by Mr. Tilden, however, showed the "saturation very uneven; absorptive power, high; block contains soluble salts of copper, removable by washing."

It was expected that the double solution, by forming an insoluble compound, would prove an effective protection against the teredo. Experiments Nos. 4, 5, 6, and 8, however, proved the contrary to be the fact.

The process, when well done, gave moderately satisfactory results against decay. A pavement laid in the yard of the Schlitz Brewing Company, in Milwaukee (experiment No. 7), was sound in 1882, after some six years' exposure. A report by Mr. J.F. Babcock, a chemist of Boston (experiment No. 9), indicated favorable results, and the planks in a ropewalk at Charlestown (experiment No. 15), laid in 1879, were yet sound in 1882.

The experiments on railroad ties (Nos. 10, 11, 12, 13, 14, and 16), however, did not result satisfactorily. They seemed favorable at first, and great things were expected of them; but late examinations made on the Wabash Railroad, on the New York, Pennsylvania, and Ohio, and on the Cleveland and Pittsburg Railroad, have shown the ties to be decaying, and the results to be unfavorable.

This applies to the sulphate of copper and barium process. Mr. Thilmany has patented still another combination, in which he uses sulphate of zinc and chloride of barium, which has been noticed under the head of burnettizing.

Experiment No. 17 was tried on the Hudson River Railroad. It consisted of 1,000 sap pine ties, which had been impregnated in the South, by the Boucherie process, with a mixture of sulphate of iron and sulphate of copper, under Hamar's patent. These ties were laid in the tunnel at New Hamburg, a trying exposure, and when examined, in 1882, several of them were still in the track. The process, however, was found to be so tedious that it was abandoned after a year's trial, and has not since been resumed.

In 1882 Mr. H. Fladd, of St. Louis, patented a method which is the inverse of the Boucherie process (experiment No. 18). To the cap fastened to the end of a freshly cut log he applies a suction pump, and placing the other end into a vat, filled with the desired solution, he sucks up the preserving fluid through the pores or sap cells of the wood.

Quite a number of experimental ties have been prepared in this way, with various chemical solutions, chief of which was sulphate of copper, and there is probably no question but that the life of the wood will be materially increased thereby.

Whether the process will prove more convenient and economical than the original Boucherie process can only be determined by practical application upon an extensive scale.

A considerable number of modifications and appliances for working the Boucherie process have been patented in this country; but none of them seems to have come into practical use, probably because of the necessity for operating upon freshly cut logs, and the inconvenience of such applications.

The table on this page gives a record of various experiments with miscellaneous substances.

RECORD OF AMERICAN EXPERIMENTS—MISCELLANEOUS.

COMMENTS ON MISCELLANEOUS EXPERIMENTS.

Experiments Nos. 1, 2, and 3 relate to the Earle process, from which great results were expected from 1839 to 1844. It consisted in immersing timber, rope, canvas, etc., in a hot solution of one pound of sulphate of copper and three pounds of sulphate of iron mixed in twenty gallons of water. It was first tested on some hemlock paving blocks on Chestnut Street, Philadelphia, and for a time seemed to promise good results. Experiments with prepared rope, exposed in a fungus pit, by Mr. James Archbald, Chief Engineer of the Delaware and Hudson Canal, seemed also favorable.

The process was, therefore, thoroughly tried at the Watervliet Arsenal, where it was applied to some 63,000 cubic ft. of timber, at a cost of about seven cents per cubic foot. The timber was used for various ordnance purposes, and while it was found to have its life extended, as would naturally be expected from the known character of the antiseptics used, its strength was so far impaired, and it checked and warped so badly, that the process was abandoned in 1844.

The committee is indebted to General S.V. Benet, Chief of Ordnance, for a full copy of the reports upon these experiments.

Experiments Nos. 4 and 7 represent the lime process, which has been applied to a considerable extent in France. The fact that platforms and boxes used for mixing lime mortar seem to resist decay has repeatedly suggested the use of lime for preserving timber. In 1840 Mr. W.R. Huffnagle, Engineer of the Philadelphia and Columbia Railroad, laid a portion of its track on white pine sills, which had been soaked for three months in a vat of lime-water as strong as could be maintained. Similar experiments were tried on the Baltimore and Ohio in 1850. The result was not satisfactory, as might be expected from the fact that lime is a comparatively weak antiseptic (52.5 by atomic weight, while creosote is 216), and from the extreme tediousness of three months' soaking.

Experiments Nos. 5 and 8 were tried with sulphate of iron, sometimes known as payenizing, and the particulars of the former have been furnished by Mr. I. Hinckley, President of the Philadelphia, Wilmington, and Baltimore Railroad, to whom your committee is much indebted for a large mass of information on the subject of timber preservation.

Mr. Hinckley has had longer and more varied experience on this subject than any other person in this country. Beginning with sulphate of copper in 1846, following with chloride of mercury in 1847, and chloride of zinc in 1852, going back to chloride of mercury, and again to chloride of zinc, using the latter until 1865, then using creosote to protect the piles against the teredo at Taunton Great River (experiment No. 2. creosoting), he has had millions of feet of timber and lumber prepared by the various processes, and has kindly placed at our disposal many original reports in manuscript and pamphlets which are now very rare.

Experiment No. 6 was made by Mr. Ashbel Welch, former President of this Society, and consisted in boring hemlock track sills 6 × 12 with a 1-1/8 inch auger-hole 10 inches deep every 15 inches. These were filled with common salt and plugged up, as is not infrequently done in ship-building, but while the life of the timber was somewhat lengthened, it was concluded that the process did not pay.

Salt has been experimented with numberless times. It is cheap, but is a comparatively weak antiseptic, its atomic weight being 58.8 in the hydrogen scale, as against 135.5 for chloride of mercury.

Experiment No. 9 is included in order to notice the well-known and most ancient process of charring the outside of timber. In this particular case, the fence posts after charring were dipped for about three feet into a hot mixture of raw linseed oil and pulverized charcoal, which probably acted by closing the sap cells against the intrusion of moisture, which, as is well known, much hastens decay. The posts, which had been set butt-end upward, were mostly sound in 1879, after 24 years' exposure.

Experiments Nos. 41, 42, 43, and 44 did not, however, result as well, and numberless failures throughout the country attest that charring is uncertain and disappointing in its results.

Much ingenuity has been wasted in devising and patenting machinery for charring wood on a large scale to preserve it against decay. The process, however, is so tedious in comparison with the benefits which it confers, and the charred surface is so objectionable for many uses, that nothing is to be expected from the process upon a large commercial scale.

In 1857-58 Mr. H.K. Nichols tried sundry experiments (No. 10), at Pottsville, Pa., upon timber which he endeavored to impregnate with pyrolignite of iron by means of capillary action. Similar experiments had previously been thoroughly tried in France by Dr. Boucherie, but the result has not been found satisfactory.

In 1858 the Erie Railway purchased the right of using the Nichols patent, and erected machinery at its Owego Bridge shop for boring a 2 inch hole longitudinally through the center of bridge timbers. This continued till 1870, when the works were burned, and in rebuilding them the boring machinery was not replaced. The longitudinal hole allowed a portion of the sap to evaporate without checking the outside of the timber, and undoubtedly lengthened its life. It is believed there are yet (1885) some sticks of timber in the bridges of the road that were so prepared in 1868 or 1869.

In 1867 Mr. W.H. Smith patented a method of preserving timber, by incasing it in vitrified earthenware pipes, and filling the space between the timber and the pipe with a grouting of hydraulic cement. This was applied to the railroad bridge connecting the mainland with Galveston Island (experiment No. 12), and so well did it seem to succeed at first that it was proposed to extend the process to railroad trestlework, to fencing, to supports for houses, and to telegraph poles. But after a while the earthenware pipes were displaced and broken, the process was given up, and Galveston bridge is now creosoted.

In 1868 Mr. S. Beer patented a process for preserving wood by simply washing out the sap from its cells. Having ascertained that borax is a solvent for sap, he prepared a number of specimens by boiling them in a solution of borax. For small specimens, this answered well, and a signboard treated in that way (experiment No. 13) was preserved a long time; but when applied to large timber, the process was found very tedious and slow, and no headway has been made in introducing it.

Experiment No. 14 was brought about by accident. Some years age it was discovered that there was a strip of road in the track of the Union Pacific Railroad, in Wyoming Territory, about ten miles in length, where the ties do not decay at all. The Chief Engineer, Mr. Blinkinsderfer, kindly took up a cotton wood tie in 1882, which had been laid in 1868, and sent a, piece of it to the committee. It is as sound and a good deal harder than when first laid, 14 years before, while on some other parts of the road cottonwood ties perish in two or five years.

The character of the soil where these results have been observed is light and soapy, and Mr. E. Dickinson, Superintendent of the Laramie Division, furnishes the following analysis:

The following remarks made by the chemists who made the analysis may be of interest:

"The decay of wood arises from the presence in the wood of substances which are foreign to the woody fiber, but are present in the juices of the wood while growing, and consist of albuminous matter, which, when beginning to decay, causes also the destruction of the other constituents of the wood."

"One of the means adopted to prevent the destruction of wood by decay is by the chemical alteration of the constituents of the sap."

"This is brought about by impregnating the wood with some substance which either enters into combination with the constitutents of the sap or so alters their properties as to prevent the setting up of decomposition."

"The analysis of this soil shows that it contains large quantities of the substances (sodium, potassium chloride, calcium, and iron) most used in the different processes of preserving or kyanizing wood. It also contains much inorganic matter, which also acts as a preserving agent."

Some of the ties so preserved have been transferred to other portions of the track, and some of the soil has also been transported to other localities, so that it is hoped that in the discussion that may be expected to follow this report, some further light will be thrown on the subject by an account of the results of these experiments.

Experiments Nos. 15, 16, 17, and 18 are most instructive, and convey a useful lesson.

In 1865 Mr. B.S. Foreman patented the application of a dry powder for preserving wood, which was composed of certain proportions of salt, arsenic, and corrosive sublimate. This action was based upon an experience which he had had when, as a working mechanic of Ellisburg, Jefferson County, N.Y., in 1838, he had preserved a water-wheel shaft by inserting such a compound in powder in the body of the wood, and ascertained that it was still sound some 14 years later.

His theory of the action of his compound upon timber was briefly this:

"That all wood before it can decay must ferment; that fermentation cannot exist without heat and moisture; that the chemical property or nature of his compound, when inserted dry into wood, is to attract moisture, and this moisture, aided by fermentation, liquefies the compound; that capillary attraction must inevitably convey it through the sap ducts and medullary rays to every fiber of the stick.... Were these crystallizations salt alone, they would soon dissolve, but the arsenic and corrosive sublimate have rendered them insoluble; hence they remain intact while any fiber of the wood is left."

"The antiseptic qualities of arsenic are also well known, and have been known for centuries. Chemical analysis of the mummies of Egypt to-day shows the presence of arsenic in large quantities in every portion of their substance. Whatever other ingredients may have entered into the compound that has been so potent in preserving from decay the bodies of the old kings of Egypt, and even the linen vestments of their tombs, arsenic was most certainly one."

The mode of application used by Mr. Foreman was to bore holes two inches in diameter three-fourths of the way through sticks of square timber, four feet apart, to fill them with the dry powder, and to plug them up with a bung. For railroad ties he bored two holes two inches in diameter, six inches inside of the rails, and filled and plugged them. Fresh cut lumber and shingles were prepared by piling layers upon each other with the dry powder sprinkled between in the ratio of twenty pounds to the thousand feet of lumber. This was allowed to remain at a temperature of at least 458° F. until fermentation took place, when the lumber was considered fully "foremanized."

The process was first applied to the timber and lumber for a steamboat, and in 1879 the result was reported to be favorable. It was then applied to some ties on the Illinois Central Railroad, where it did not succeed, and to some on the Chicago and Northwestern, where they seem to have been lost sight of, being few in number, so that your committee has not been able to learn the result.

Great expectations were, however, entertained, and a conditional sale was made to various parties of the right of using the process, notably, it is said, to the Memphis and Charleston Railroad for $50,000; and some ten miles of ties were prepared on that road, when the poisonous nature of the ingredients used brought about disaster.

Some shingles were prepared for a railroad freight house at East St. Louis, but all the carpenters who put them on were taken very ill, and one of them died.

The arsenic and corrosive sublimate effloresced from the ties along the Memphis and Charleston Railroad. Cattle came and licked them for the sake of the salt, and they died, so that the track for ten miles was strewed with dead cattle. The farmers rose up in arms, and made the railroad take up and burn the ties. The company promoting foremanizing was sued and cast in heavy damages, and it went out of business.

In 1870 Mr. A.B. Tripler patented a mixture of arsenic and salt, and the succeeding year a specimen of wood prepared under that patent was submitted to the Board of Public Works of Washington, D.C., and examined by its chemist, Mr. W.C. Tilden (experiment 19). He found the impregnation uneven, and the absorptive power high, but he did not find any arsenic, though its use was claimed.

The Samuel process (experiment 20) consisted in the injection, first, of a solution of sulphate of iron, and afterward of common burnt lime. Mr. Tilden reported the wood to be brittle, and the water used to test the absorptive power to have been filled with threads of fungi in forty-eight hours.

The Taylor process (experiment No. 21) used a solution of sulphide of calcium in pyroligneous acid. It was condemned by Mr. Tilden.

The Waterbury process (experiment 22) consisted in forcing in a solution of common salt, followed by dead oil or creosote. It was also condemned by Mr. Tilden.

The examinations of Mr. Tilden extended to some fourteen different processes, most of which have already been noticed in this report, and their practical results given.

The Board of Public Works, however, laid down a considerable amount of prepared wood pavement in Washington, all of which is understood to have proved a dismal failure. After a good deal of inquiry, your committee has been enabled to obtain information of the results of three of these experiments.

The pine paving blocks upon Pennsylvania Avenue (experiment 23) were first kiln-dried, and then immersed in a hot solution of sulphate of iron.

The spruce blocks on E Street (experiment 24) were treated with chloride of zinc, or, in other words, burnettized; but the mode of application is not stated.

The pine blocks upon Sixteenth Street (experiment 25) were treated with the residual products of petroleum distillation. It is stated that this was the only process in which pressure was used.

In from three and a half to four and a half years the blocks were badly decayed, and large portions of the streets were almost impassable, while other streets paved in the same year with untreated woods remained in fair condition.

It has been stated to your committee that this result, which did much toward bringing all wood preserving processes into contempt, was chiefly owing to the very dishonest way in which the preparation was done; that in fact there was a combination between the officials and the contractors by which the latter were chiefly interested "how not to do it," and that the above results, therefore, prove very little on the subject of wood preservation.

Through the kindness of the United States Navy Department your committee is enabled to give the results of a series of experiments (Nos. 26 to 41 inclusive) which have been carried on at the Norfolk, Va., Navy Yard, for a series of years, by Mr. P.C. Asserson, Civil Engineer, U.S.N., to test the effect of various substances as a protection against the Teredo navalis. It will be noticed that the application of two coats of white zinc paint, of two coats of red lead, of coal tar and plaster of Paris mixed, of kerosene oil, of rosin and tallow mixed, of fish oil and tallow mixed and put on hot, of verdigris, of carbolic acid, of coal tar and hydraulic cement, of Davis' patent insulating compound, of compressed carbolized paper, of anti-fouling paint, of the Thilmany process, and of "vulcanized fiber," have proved failures.

The only favorable results have been that oak piles cut in the month of January and driven with the bark on have resisted four or five years, or till the bark chafed or rubbed off, and that cypress piles, well charred, have resisted for nine years.

This merely confirms the general conclusion which has been stated under the head of creosoting, that nothing but the impregnation with creosote, and plenty of it, is an effectual protection against the teredo. Numberless experiments have been tried abroad and in this country, and always with the same result.

There are quite a number of other experiments which your committee has learned about which are here passed in silence. The accounts of them are vague, or the promised results of such slight importance as not to warrant cumbering with them this already too voluminous report.

The committee also forbears from discussing the merits of the many patents which have been taken out for wood preservation. It had prepared a list of them, and investigated the probable success of many of them, but has concluded that it is better to confine itself to the results of actual tests, and to stick to ascertained facts.

Neither does the committee feel called upon to point out the great importance of the subject, and the economical advantages which will result from the artificial preparation of wood as its price advances. They hope, however, that the members of this Society, in discussing this report, will dwell upon this point.

We shall instead give as briefly as possible the general conclusions which we have reached as the result of our protracted investigation.

DECAY OF TIMBER.

Pure woody fiber is said by chemists to be composed of 52.4 parts of carbon, 41.9 parts of oxygen, and 5.7 parts of hydrogen, and to be the same in all the different varieties. If it can be entirely deprived of the sap and of moisture, it undergoes change very slowly, if at all.

Decay originates with the sap. This varies from 35 to 55 per cent. of the whole, when the tree is felled, and contains a great many substances, such as albuminous matter, sugar, starch, resin, etc., etc., with a large portion of water.

Woody fiber alone will not decay, but when associated with the sap, fermentation takes place in the latter (with such energy as may depend upon its constituent elements), which acts upon the woody fiber, and produces decay. In order that this may take place, it is believed that there must be a concurrence of four separate conditions:

1st. The wood must contain the elements or germs of fermentation when exposed to air and water.

2d. There must be water or moisture to promote the fermentation.

3d. There must be air present to oxidize the resulting products.

4th. The temperature must be approximately between 50° and 100° F. Below 32° F. and above 150° F., no decay occurs.

When, therefore, wood is exposed to the weather (air, moisture, and ordinary temperatures), fermentation and decay will take place, unless the germs can be removed or rendered inoperative.

Experience has proved that the coagulation of the sap retards, but does not prevent, the decay of wood permanently.³ It is therefore necessary to poison the germs of decay which may exist, or may subsequently enter the wood, or to prevent their intrusion, and this is the office performed by the various antiseptics.

We need not here discuss the mooted question between chemists, whether fermentation and decay result from slow combustion (eremacausis) or from the presence of living organisms (bacteria, etc.); but having in the preceding pages detailed the results of the application of various antiseptics, we may now indicate under what circumstances they can economically be applied.

(To be continued).

[2]

From the Transactions of the Society.

[3]

Angus Smith, 1869, "Disinfectants." S.B. Boulton, 1884, Institution Civil Engineers, "On the Antiseptic Treatment of Timber."