Among the many problems arising from the use of steel in naval construction, none is more important than that of protecting the under-water body of a vessel from the corrosive action of sea-water. The problem is a modification of the old one of protecting the bottoms of wooden or iron vessels, as steel is much more liable to corrosion under water than iron, and steel vessels, being generally constructed of much lighter scantling, are proportionally more injured by an equal amount of chemical action. So far as the purposes of construction are concerned, no material equals steel; but if steel ships cannot be protected against the destructive action of the medium in which they must exist, the question assumes another phase, and economical results might be obtained by reverting to iron or wood. As, however, the use of steel enables the naval architect to obtain results in speed and strength and lightness of hull which are otherwise unobtainable, this reversion is practically out of the question. Steel must be used and protected.
In General Information Series No. VII., Lieutenant Schroeder gives a most complete and interesting resume of the whole question of protection of the hulls of vessels. He refers on page 277 to the process of lacquering, which has been tried on several of the vessels of the Japanese navy, but without giving any details. It has been my good fortune while on the Asiatic Station to meet Mr. Hotta, and to receive from him quite full information as to his process of lacquering; and I have also had an opportunity, through the courtesy of the officials of the Yokosuka dockyard, of inspecting two of the vessels of the Japanese navy while in dock for the purpose of receiving or renewing their lacquer coats. It was thought that the information thus obtained might be of interest to the members of the Naval Institute, as having an important bearing on one of the most prominent professional problems of the day.
Nearly every book on Japan refers in greater or less detail to the subject of lacquer, but until the substance was analyzed only little was really known of it. It may not be amiss in the consideration of our subject to examine somewhat in detail into the constitution and method of preparation of lacquer, using for the purpose such published accounts as have appeared in the proceedings of scientific societies, or in the works of residents of Japan who had carefully investigated the subject. The lacquer tree is indigenous to Japan, and is also found in Corea, China, and the countries of Farther India. In Japan it is systematically cultivated. New plantations are being laid out in Japan and will commence to yield in five years, and as the whole coast country of Asia is practically available for the cultivation of the tree, it is safe to say that a great demand, such as might be caused by an extensive application of lacquer to steel or iron ships, would create its own supply.
Lacquer is obtained from the tree by making incisions in the bark. Usually several cuts are made approximately parallel to one another and at various points on the circumference. The lacquer exudes from these incisions in the form of a thick grayish juice, and is gathered by a wooden spatula. As already stated, the trees commence to yield when five years old, and yield for ten or fifteen years. An inferior lacquer is sometimes obtained by grinding the small branches and twigs of the tree, but nearly all that is used is obtained from incisions in the bark. It is purified by stirring in a tub with a wooden spatula, by which process the excess of moisture is given off and the consistency slightly increased. The pure commercial lacquer has a specific gravity of about 1.002 at 20° C, is of a grayish white color and dextrinous consistency, and possesses a characteristic sweet odor. In contact with the air it darkens and hardens, forming a film that protects the lacquer underneath. The ordinary method of application to any surface is by taking a small quantity on a wooden spatula and placing it on the surface to be lacquered, working it down into a thin uniform coat by repeated strokes with a flat camel's-hair brush, the strokes being made in different directions, but in ordinary work most commonly at right angles. The lacquer rapidly darkens to a dark brown, and afterwards dries, forming a lustrous coat. Colors are given to the lacquer coat when desirable by mixing metallic body pigments such as vermilion, cinnabar, ochre, or orpiment.
Lacquer has been frequently analyzed, with somewhat varying results. The analyses given below were made under the direction of Prof H. Yoshida, Asst. Professor of Chemistry in the Imperial University at Tokyo, and recognized as one of the best authorities on lacquer in Japan. They are from a paper contributed by Prof Yoshida to the Proceedings of the Royal Society of Edinburgh, on the Chemistry of Japanese Lacquer.
The constituents of pure lacquer are found to be a resinous acid, gum arabic, water, and a nitrogenous residue. The method of analysis adopted was to extract the resin from the lacquer by treating it with absolute alcohol, evaporating the solution and drying at 105° to 110° C. The residue was boiled with water and the extract evaporated on a water-bath, giving the amount of gum. The residue from the water solution consists of a coagulated nitrogenous substance and small quantities of coloring matter. The sum of the percentages of the above subtracted from 100 gives the amount of water and volatile matter.
The percentage composition of pure lacquer was obtained from a sample specially collected under official supervision in the province of Yoshino, celebrated for producing the best lacquer in Japan. It yielded the following results:
Soluble in alcohol (urushic acid), 85.15
Gum Arabic, 3.15
Nitrogenous matter, 2.28
Water and volatile matter, 9.42
Other unadulterated samples gave the following: Number 1 was from Hittachi, 2 from Sagami, 3 from Yechigo, 4 from Sagami, and 5 and 6 commercial lacquers, origin unknown, bought in Tokyo.
| 1. | 2. | 3. | 4. | 5. | 6. |
Urushic acid | 64.62 | 68.83 | 66.92 | 80.00 | 64.07 | 58.24 |
Gum Arabic | 5.56 | 5.02 | 4.75 | 4.69 | 6.05 | 6.32 |
Nitrogenous matter | 2.10 | 2.01 | 1.72 | 3.31 | 3.43 | 2.27 |
Oil | 0.09 | 0.06 | 0.06 | ? | 0.23 | ? |
Water and volatile matter | 27.63 | 24.08 | 26.55 | 12.00 | 26.22 | 33.17 |
| 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 |
The quality of the lacquer is determined by the amount of urushic acid. 5 and 6 are fair commercial lacquers. The common adulterations are water and oil. An excess of the former can be expelled by stirring the lacquer. Paint oils are frequently added to the lacquer to increase the transparency and covering power of resisting chemical agents, the most valuable property of lacquer, is much reduced.
The principal and by far the most important constituent of the juice is the urushic acid obtained from the alcoholic solution. It is a pasty substance of a dark brown color, of specific gravity of 0.9851 at 23°C., and having the characteristic smell of the juice. It is quite insoluble in water, and is unacted upon either in air or oxygen, but is soluble in benzene, ether, carbon bisulphide, or chloroform. It is permanent up to 160°C., but above 200° decomposes slowly with carbonization. It is very poisonous, and produces most disagreeable itching when applied to the skin, causing what is commonly known as lacquer poisoning. It is probable that this poisoning is also partly due to a volatile substance given off in the drying of the alcohol solution. When produced by the urushic acid, the best remedy is a strong solution of acetate of lead, which forms a urushiate of lead. This is, when formed from solution, a grayish flocculent precipitate.
Urushic acid dried at 100°C was analyzed by Mr. Hiraga, and the analysis communicated by Prof. Roscoe to the Manchester Literary and Philosophical Society, as follows:
| I. | II. | Mean. | Required by theory for C14H18O2. |
Carbon | 77.09 | 77.01 | 77.05 | 77.06 |
Hydrogen | 9.28 | 8.75 | 9.01 | 8.28 |
Oxygen | 13.63 | 14.24 | 13.94 | 14.66 |
| 100.00 | 100.00 | 100.00 | 100.00 |
Prof. Yoshida examined many of the metallic salts of urushic acid. They are readily obtained from the alcoholic solution. The iron salts are quite complex and numerous. A small quantity of one of these salts added to ordinary lacquer produces the black lacquer of commerce. Long-continued action of strong hydrochloric acid on urushic acid produced an isomeric form, a ?-urushic acid. Chlorine and bromine produced series of substitution products, as did also nitric acid. Many other interesting chemical compounds were obtained, but their consideration is foreign to the present subject.
The gum in the lacquer juice seems to be in the form of gum arable. An examination gave the following results:
|
| Arabic Acid (C12H22O11). |
Carbon | 42.47 | 42.11 |
Hydrogen | 6.40 | 6.43 |
Oxygen | 51.13 | 51.46 |
| 100.00 | 100.00 |
The physical properties of the gum are those of gum Arabic. It exists in the juice in the form of an aqueous solution, and even in hardened lacquer the gum can be extracted by treating it for a long time with water. As it is not therefore an essential part of the varnish, its function appears to be to keep the different constituents of the juice in a state of uniform distribution, and also to assist the adhering power of the lacquer when applied to a surface.
The most important practical question connected with lacquer is that of the drying. Prof. Yoshida examined this most carefully, and his experiments appear to be convincing. It was found, as already stated, that the urushic acid was permanent in air, nor did a mixture of the acid and the gum in the proportions in which they exist in the juice show any tendency to harden. The hardening was found to occur only in the presence of the nitrogenous matter that remained after the urushic acid and gum Arabic had been extracted from the juice by absolute alcohol and boiling water. The residue thus obtained is a coagulated albuminous substance, having no action whatever on urushic acid. If, however, the gum is extracted by cold water, the residue shows very marked diastatic properties. Its analysis is as follows:
| I. | II. | Mean |
Carbon | 59.52 | 59.72 | 59.62 |
Hydrogen | 7.62 | Lost | 7.62 |
Nitrogen | 5.48 | … | 5.48 |
Oxygen | 26.18 | … | 26.18 |
Ash | 1.20 | … | 1.20 |
| 100.00 | … | 100.00 |
The substance is slightly soluble in water, and in sodium chloride and weak alkaline solutions. It does not act on sugar solution or gelatinized starch.
Previous experiments having shown that lacquer deprived of this nitrogenous matter would not dry, two series of experiments were made to determine the practical conditions under which the diastatic action of the albuminoid was best carried on. In the first, a small quantity of pure lacquer juice was heated on a water-bath, and the heated juice was then laid in a thin layer on a glass plate and put in a box, the air of which was kept moist. The temperature of the box was kept at 20°C.
- The ordinary juice dried at 20°C in 3 ½ hours in air, and in somewhat less than 2 hours in moist oxygen.
- The juice heated to 30°C dried in 4 hours.
- The juice heated to 40°-43°C dried in 4 ½ hours.
- The juice heated to 50°C—dry time not known.
- The juice heated to 55°-59°C dried in 24 hours.
- The juice heated to above 60°C did not dry.
In juice containing a larger proportion of the albuminoid and water the upper limit has gone as high as 73°c, beyond which no drying took place. The lower limit has been found to be 0°-2°C, but this loss of activity is only temporary, the lacquer drying readily as the temperature rises. The upper limit being that of the coagulation of the albuminoid, the diastatic action ceases completely.
The second series of experiments was designed to illustrate the nature of the chemical action involved in drying. Samples of juice were put under bell glasses containing different gases, at the temperature of 13°-15°C with the following results:
- In dry air the sample did not dry.
- In moist air the sample dried in 4 hours.
- In dry oxygen the sample did not dry.
- In most oxygen the sample dried in 2 ½ hours.
- In dry hydrogen the sample did not dry.
- In moist hydrogen the sample dried imperfectly in a day and a half.
- In dry carbonic acid the sample did not dry.
- In moist carbonic acid the sample dried in two days.
- In dry nitrogen the sample did not dry.
- In moist nitrogen the sample dried imperfectly in a day and a half.
More careful experiments made in hydrogen and carbonic acid in eudiometers standing over mercury showed that the lacquer would not dry.
As the result of these experiments the inference is legitimately drawn that the presence of oxygen and moisture is necessary for the drying of lacquer, and that the action is best carried on at a temperature of about 20° C, ceasing at the limits of 0° and 70°.
In order to determine the exact nature of the chemical action involved in the drying, a specimen of pure juice was taken, rapidly heated over the water-bath so as to coagulate the albuminoid, and the heating continued long enough to expel all water. Analysis then gave the following:
Carbon 75.54
Hydrogen 8.97
Nitrogen 0.11
Ash 0.21
Oxygen 15.17
100.00
Lacquer naturally dried was heated to 100° C. and analyzed:
Carbon 70.87
Hydrogen 8.225
Nitrogen 0.092
Ash 0.032
Oxygen 20.781
100.00
The general action in drying is, therefore, that the lacquer takes up oxygen, and Prof. Yoshida states that the difference between the analyses is accounted for by the supposition that each molecule of urushic acid, C14H18O2, has taken up one atom of oxygen and changed into oxy-urushic acid, C14H18O3. To test further this supposition, urushic acid was repeatedly subjected to the action of strong chromic acid containing an excess of sulphuric acid. The product was cohobated with alcohol to dissolve the unattacked urushic acid, and dried at 106°C. The result was a brown powder. The mean of four analyses of this substance as compared with the theoretical composition of oxy-urushic acid is as follows:
| Mean | C14H18O3 |
Carbon | 71.61 | 71.79 |
Hydrogen | 7.94 | 7.69 |
Oxygen | 20.45 | 20.52 |
| 100.00 | 100.00 |
This oxy-urushic acid is a very stable substance, being unacted upon by any reagent except hot fuming nitric acid, which gradually changes it into a yellowish spongy substance, C9H18(COOH)4. It is to the presence of this oxy-urushic acid in hardened lacquer that its strength and durability are due.
Prof. Yoshida sums up the chemistry of lacquer in the following words:
- “Lacquer juice consists essentially of four substances; viz., urushic acid, gum, water, and nitrogenous matter.
- “The main constituent, urushic acid, is a stable acid, capable of forming many well-defined salts and derivative compounds.
- “The gum is probably identical with gum Arabic.
- “The nitrogenous matter has a composition allied to albumen, with much less nitrogen, and has a peculiar diastatic property.
- “The hardening of the juice is due to the oxidation of urushic acid (C14H18O2), into oxy-urushic acid (C14H18O3), which is effected by the aid of the nitrogenous matter in presence of oxygen and moisture.
- “The hardening can only take place within narrow limits of temperature, viz., between 0° and 2°C, on one side, and the temperature of the coagulation of the albuminoid (60° to 70°C) on the other.
- “The gum is essential in keeping up the emulsion and uniform distribution of the constituents; but in the hardened lacquer it is injurious, causing blisters on newly lacquered ware when treated with water for a length of time.
- “Any quality can be conveniently given to the juice by the addition of pure urushic acid, which brings down the relative amounts of gum and nitrogenous matter. The lacquer becomes thus more transparent and gains in strength.
- "The mixture of 20 to 25 per cent of drying oil with the juice does not much impair the essential quality of the lacquer."
THE LACQUERING OF SHIPS.
The idea of lacquering iron and steel vessels as a protection against the action of sea-water was suggested to Mr. Hotta, a lacquer manufacturer of Tokyo, by the observation that pieces of old lacquer recovered from the sea showed but little action, the lacquer being practically unattacked. As the Japanese were then purchasing iron and steel ships from abroad, and were encountering the same difficulties that were met with elsewhere in protecting the metal, experiments were made on special test-plates, which were immersed in seawater for considerable periods, generally at the Yokosuka dockyard. The first results obtained were not fully satisfactory, but were very encouraging, and the tests were continued, varying slightly the composition of the lacquer, or adding chemicals to assist in obtaining the desired results. In June, 1886, a practical test was made by lacquering about 1200 feet of the bottom of the Fuso-Kan, using the preparation of lacquer that at that time had given the best results. The ship was docked again in September, 1887, and the condition of the lacquered portion was so satisfactory that the Admiralty gave an order to lacquer the whole bottom. In December, 1888, the ship was again docked, but the lacquer coat was found to be so good that no repairs were made. In June, 1889, the ship was again docked, the lacquer being still satisfactory. In each case anti-fouling paint was applied over the lacquer. The Fuso was docked once more in April, 1890, and although the lacquer covering was almost perfect, it was for some unknown reason all removed by scraping, and the bottom was painted.
Many other vessels of the Japanese Navy have since been lacquered, a list being appended. Experimentation has been going on continually. The work is all done by Messrs. Hotta & Co., they holding a monopoly under the laws of Japan, practically the equivalent of an American patent. Not content with merely protecting the metal against corrosion, the contractors have endeavored to meet all the requirements of the case by providing an anti-fouling lacquer preparation, as well as an anti-corrosive, the use of metallic anti-fouling paints over the lacquer having been found to be injurious, the urushic acid of the lacquer sometimes attacking the metallic base of the paint, resulting in the practical destruction of the useful qualities of both. This preparation was developed experimentally, and test-plates coated with both protective and anti-fouling lacquers having given most satisfactory results immersed in sea-water at Yokosuka for eighteen months, the Japanese Admiralty ordered the lacquering of the new despatch-vessel Yaeyama with both kinds of lacquer. The work was performed in July, 1890, and the result will be watched with interest, as the test-plates remained perfectly clean; and if the same protection is afforded to the Yaeyama under the ordinary conditions of service, the anti-fouling lacquer will have vindicated its claim to be the equal if not the superior of any similar composition known.
The protective or anti-corrosive lacquer is mainly lacquer, small quantities of some inert minerals like mica or kaolin being added to increase the covering power and body of the preparation. The composition of the different coats differs somewhat, that applied directly to the skin of the ship containing the largest proportion of lacquer.
In the first experiments special pains were taken to have the plates perfectly clean, the metal being washed off with acid in order to remove all oxides, but this process was soon discontinued, as the lacquer coats when applied to the clean iron were found to blister considerably. In later experiments the steel was merely brushed clean, removing all non-adherent oxides or films, the lacquer being applied over all adherent substances. An important point in which lacquer differs from ordinary protective compounds is in its insulating power against galvanic action. It is well known that if a steel plate having magnetic oxide of iron on its surface be exposed to sea-water, a strong galvanic couple is set up between the oxide and the steel, underneath the protective covering, and pitting of the metal results. With lacquer the case is different. Lacquer has no chemical action on the magnetic oxide; and if the plate is dry when it is applied, galvanic action is prevented by the waterproof and insulating properties of the lacquer coat. The exclusion of water prevents any action whatever, and the best results with the test-plates have been obtained on plates on which the presence of the magnetic oxide was ignored. The removal of this oxide, which is ordinarily considered necessary, is therefore avoided.
The method of lacquering is as follows: The ship is docked and the bottom carefully scraped of all yellow rust, old paint, or other matter that is not strongly adherent. If old paint adheres firmly, it is considered unnecessary to remove it. The bottom of the ship is then shut in by screens of old canvas suspended from just above the water-line to the bottom of the dock. In winter, stoves or other heating apparatus are placed inside this screen to raise the temperature and thus facilitate the drying of the lacquer. It has been proposed to allow exhaust steam to escape inside the canvas screen to secure the requisite warmth and moisture for the drying; but although this practice is common in lacquer manufactories, it has not yet been tried on ships. In summer, the screen around the bottom is necessary in order to screen the metal from the direct rays of the sun, which might raise the temperature to such a point as to impair the lacquer by a partial coagulation of the albumen. With the screen in place, the lacquering can be carried on in almost any weather. When everything is in readiness, the first coat of protective lacquer is applied, and worked down into a smooth uniform coating by a soft brush, as already described. One man can lacquer about 500 square feet, one coat, in eight hours. The time of drying of the first coat, which, as already stated, is almost pure lacquer, may vary from three or four hours to one day, according to the temperature and moisture of the air. In cold weather the drying process is tedious.
As soon as the first coat is dry the second is applied. This may contain mica or kaolin in small quantities, as also the outer protective coats. Five protective coats have generally been applied to the Japanese men-of-war, but a smaller number may be used when the anti-fouling lacquer is applied over them. The inner coat of the anti-fouling preparation is principally lacquer, the amount of poisonous mercury salt contained in the preparation increasing with each coat. The only ship that has thus far received both preparations, the Yaeyama, has four coats of the protective and three of the antifouling.
The number of coats considered necessary is at least three of the protective and the same number of the anti-fouling lacquer. Under favorable circumstances the ship would not be in dock more than six days, but ten would be more probable. The cost of the lacquering is stated by the contractors as five yens for thirty-six square feet, about thirteen cents U. S. gold per square foot. If the work were to be carried on more generally, the expense could be reduced, as a permanent corps of employees have to be maintained, although frequently out of work. Work has been done at much less than the above rates. The chief, in fact the only serious, objection to the use of lacquer is the expense. If dockage is cheap, this is not excessive, but the long time involved for the proper drying of the lacquer coats renders the operation a very costly one when the dock charges are high. The vital question is whether the protection afforded is worth the expense. If absolutely complete, preventing all deterioration or fouling of the hull, it would be economy to pay the highest charges in order to have the vessel always sound and in condition for service. It is just becoming known outside of professional circles that steel vessels are expensive, and that more money may be spent in excessive coal bills in trying to force a foul hull through the water than would be expended with proper economy in the frequent dockings necessary for keeping the hull clean.
It cannot be said with certainty that the use of lacquer is more expensive than the ordinary methods of protection. This depends very largely, of course, on the dry-dock charges. The contractors claim that one thorough lacquering of a vessel's bottom will keep it clean and protect the metal for three years. The expense of this operation may be figured up as follows:
Taking the Charleston, for instance, we have:
Cost of cleaning and lacquering 20,000 sq. ft. at 13 cents, $2600
Docking and nine "lay days," $4300
$6900
For painting and cleaning, we have:
Docking and one "lay day," $1400
Painting, etc., (estimated) $600
$2000
Allowing the claim of the contractors that one lacquering is sufficient for three years, and taking the common estimate that a steel ship should be docked every six months at least, the total cost for three years is:
Lacquering $6,900
Painting $12,000
These prices are for Yokosuka dockyard. Accepting the data in Naval Constructor Hichborn's article on the "Sheathing of Ships" in relation to the work on the Chicago in government docks, we have the cost of one docking and painting at New York as follows:
Docking $400
Painting, $1000
$1400
Assuming that the cost of lacquering in the United States would be twice that in Japan, we have:
Docking, $400
Lacquering 21,000 sq. ft. at 26 cents, $5460
$5860
Taking the cost as before for three years, we have:
Painting $1400 X 6 = $18400
Lacquering 5860
It may be questioned whether the lacquer will last three years, and it is also possible that the painted ship would need docking oftener than once in six months. In the absence of data a careful estimate is impossible, but enough has been shown to render the statement probable that protection by lacquer is not in the long run expensive.
The experience of the Japanese navy must be largely relied on, and the unanimous testimony of all the naval officers whom I have met is that lacquer affords excellent protection to the hull, but is expensive. It is noticeable that the work is being continued in the Japanese navy in spite of the expense.
Through the courtesy of the officials of the Yokosuka dockyard I was allowed to inspect the condition of the lacquered bottom of the Takatchiho in January, 1890, the ship having been in the water since May, 1889. The water-line belt had been lacquered in September, 1886, and repaired in May, 1889, when the rest of the ship was lacquered, as a result of the good condition in which the belt was then found. When the bottom was examined in January, 1890, it was found that on the bilge and floor plates the lacquer was perfectly smooth and unbroken and had afforded complete protection to the metal. On the sides below the water line there were numerous small blisters, averaging about a quarter of an inch in diameter; but these were dry inside, the lacquer coat being unbroken and the metal underneath was bright and uncorroded. Occasionally larger blisters were found which contained water, the film of lacquer having become broken. Underneath these the metal was dull but uncorroded, and there were no signs of rust. In cases where the lacquer had been scraped off, rust cones had formed, and their position marked the number of breaks that had occurred in nine months. In the entrance, especially in the wake of the anchors and chains, the lacquer was considerably broken and the metal consequently rusted, but in no part of the hull was there any extensive corrosion or pitting, except underneath the lacquer, showing that it antedated the application of the lacquer in May, 1889. An interesting feature illustrating the effect of the lacquer in preventing galvanic action existed in the starboard side of the run, where some of the plates showed extensive corrosion under the lacquer, apparently the result of galvanic action between the steel and the propeller and its fittings. Here was not a single rust spot, showing that no corrosion had taken place since the application of the lacquer.
The impressions derived from the appearance of the bottom of the Takatchiho were that lacquer is a perfect protection against the action of sea-water, so long as the coat remains unbroken. Although much more elastic and adherent than any kind of paint can be, it is somewhat susceptible to mechanical injury, and especially so forward where the anchors and chains and the impact of floating bodies are liable to break it. Every break becomes a spot of corrosive action or pitting. As it seems impossible to prevent this injury, and as the protection afforded by the lacquer is that of the worst portion, it would seem desirable in practice to dock the ship oftener than once in three years for examination and, if necessary, for repairs to the lacquer coat. If this were done, the metal of the ship would suffer but little deterioration.
Another use of lacquer that has not been tried as yet is as a substitute for cement on the inside of ships and for the protection of the inner skin throughout. There can be no question that its use here would prevent all rusting, as it seems absolutely unalterable in air. It has been used with success as a substitute for galvanizing, and seems to admit of numerous applications in places where metal is to be protected against the chemical action of gases.
Messrs. Hotta & Co. are making preparations for carrying on the lacquering of ships in other countries than Japan, and it is possible that in the near future the process may become widely known.
MEN-OF-WAR LACQUERED BY MESSRS. HOTTA & CO.
Japanese.
Fuso.—June, 1886, 1224 sq. feet lacquered for trial. Sept., 1887, entire bottom lacquered. Dec, 1888, docked but no repairs made. June, 1889, slight repairs made. March, 1890, lacquer scraped off.
Riujo.—April, 1888, armor shelf lacquered. A wooden ship copper sheathed; armor belt much corroded.
Tsukushi.—August, 18S7, entire bottom lacquered. June, 1888, docked but no repairs. Feb., 1889, slight repairs.
Naniwa.—Sept., 1886, 5200 sq. feet (water-line belt) lacquered. May, 18S8, additional surface lacquered. Feb., 1889, entire bottom lacquered.
Takatchiho.—Sept., 1886, water-line belt lacquered. May, 1889, entire bottom lacquered. Jan., 1890, docked and slight repairs made.
Atago.—May, 1889, entire bottom lacquered. Torpedo-boats 1, 2, 3, 4, 5.—April, 1887, entire bottom lacquered. These boats have all been docked since and slight repairs made as necessary.
Kotaka.—Sept., 1888, entire bottom lacquered.
The above were lacquered with the anti-corrosive preparation only, generally five coats. Metallic anti-fouling paint was used over the lacquer, and the vessels had to be docked to renew this paint.
Yaeyama.—July, 1890, entire bottom lacquered with four coats of protective and three of anti-fouling preparations.
Russian.
Battle-ship Dmitri Donskoi.—Nov., 1886, armor belt partly lacquered. Nov., 1887, armor belt wholly lacquered. Oct., 1888, lacquer on steel portions was found to be in very good condition. On the zinc sheathing it had been detached through the action of the urushic acid on the zinc.
Admiral Nakhimoff.—Aug., 1889, steel armor belt found to be very much corroded and was therefore lacquered.
NOTE BY LIEUT.-COMMANDER CLIFFORD H. WEST, U.S.N.
Messrs. Hotta and Company of Tokyo, Japan, have sent two plates to the United States for trial by the U. S. Navy Department. One plate is of steel and one of iron, each four feet square, and covered with three coats of anti-corrosive and three coats of anti-fouling lacquers. These plates arrived at New York City in November, 1890. Chief Constructor T. D. Wilson, U. S. Navy, has directed that the plates be submerged in tide water at the Navy Yard, New York, for a period of three months, when they are to be taken up, and a report made to the Bureau of Construction and Repair as to their condition.