Chapter 5

The mode of applying the paint, varnish, or wash will also depend upon the circumstances of the case. For example, it may be applied by a brush, as in ordinary painting, or by dipping or steeping the article in the paint, varnish, or wash; or a block or type may be used to advantage, as in calico-printing and the like. For outdoor work, or wherever the surface illuminated is exposed to the vicissitudes of weather or to injury from mechanical contingencies, it is desirable to cover it with glass, or, if the article will admit of it, to glaze it over with a flux, as in enameling, or as in ordinary pottery, and this may be accomplished without injury to the effect, even when the flux or glaze requires a red heat for fusion.

Among other applications of the said invention which may be enumerated, it is particularly advantageous for rendering visible clock or watch faces and other indicators--such, for example, as compasses and the scales of barometers or thermometers--during the night or in dark places during the night time. In applying the invention to these and other like purposes there may be used either phosphorescent grounds with dark figures or dark grounds and phosphorescent figures or letters, preferring the former. In like manner there may be produced figures and letters for use on house-doors and ends of streets, wherever it is not convenient or economical to have external source of light, signposts, and signals, and names or marks to show entries to avenues or gates, and the like.

The invention is also applicable to the illumination of railway carriages by painting with phosphorescent paint a portion of the interior, thus obviating the necessity for the expense and inconvenience of the use of lamps in passing through tunnels. It may also be applied externally as warning-lights at the front and end of trains passing through tunnels, and in other similar cases, also to ordinary carriages, either internally or externally. As a night-light in a bed-room or in a room habitually dark, the application has been found quite effectual, a very small proportion of the surface rendered phosphorescent affording sufficient light for moving about the room, or for fixing upon and selecting an article in the midst of a number of complicated scientific instruments or other objects.

The invention may also be applied to private and public buildings in cases where it would be economical and advantageous to maintain for a short time a waning or twilight, so as to obviate the necessity for lighting earlier the gas or other artificial light. It may also be used in powder-mills and stores of powder, and in other cases where combustion or heat would be a constant source of danger, and generally for all purposes of artificial light where it is applicable.

In order to produce and maintain the phosphorescent light, full sunshine is not necessary, but, on the contrary, is undesirable. The illumination is best started by leaving the article or surface exposed for a short time to ordinary daylight or even artificial light, which need not be strong in order to make the illumination continue for many hours, even twenty hours, without, the necessity of renewed exposure.

The advantages of the invention consist in obtaining for the purposes of daily life a light which is maintained at no cost whatever, is free from the defects and contingent dangers arising from combustion or heat, and can be applied in many cases where all other sources of light would be inconvenient or incapable of application.

Heretofore phosphorus has been mixed with earthy oxides, carbonates, and sulphates, and with oxides and carbonates of metal, as tin, zinc, magnesia, antimony, and chlorides of the same, also crystallized acids and salts and mineral substances, and same have been inclosed and exhibited in closely-stopped bottles as a phosphorus; but such union I do not claim; but what I claim is:

A luminous paint, the body of which is a phosphorescent substance, or composed in part of such substance, the vehicle of which is such as is ordinarily used in paints, viz., one which will become dry by oxidation or evaporation, substantially as herein described.

A. Krause, of Buffalo, N.Y., obtained a patent for improvement in phosphorescent substances dated December 30, 1879. The patentee says: This invention relates to a substance which, by exposure to direct or indirect sun-light, or to artificial light, is so affected or brought into such a peculiar condition that it will emit rays of light or become luminous in the dark.

It is a well-known fact that various bodies and compositions of matter, more especially compositions containing sulphur in combination with earthy salts, possess the property of emitting rays of light in the dark after having been exposed to sun-light. All of these bodies and compositions of matter are, however, not well adapted for practical purposes, because the light emitted by them is either too feeble to be of any practicable utility, or because the luminous condition is not of sufficient duration, or because the substances are decomposed by exposure to the atmosphere.

Among the materials which have been employed with the best results for producing these luminous compositions are sea-shells, especially oyster-shells. I have found by practical experiments that only the inner surface of these shells is of considerable value in the production of luminous compositions, while the body of the shell, although substantially of the same chemical composition, does not, to any appreciable extent, aid in producing the desired result. It follows from this observation that the smallest shells, which contain the largest surface as compared with their cubic contents, will be best adapted for this purpose.

I have found that chalk, which is composed of the shells of microscopic animals, possesses the desired property in the highest degree; and my invention consists, therefore, of a luminous substance composed of such chalk, sulphur, and bismuth, as will be hereinafter fully set forth.

In preparing my improved composition I take cleaned or precipitated chalk, and subject it to the process of calcination in a suitable crucible over a clear coal or charcoal fire for three or four hours, or thereabout. I then add to the calcined chalk about one-third of its weight of sulphur, and heat the mixture for from forty-five to ninety minutes, or thereabout. A small quantity of bismuth, in the proportion of about one per cent, or less of the mixture, is added together with the sulphur.

The metal may be introduced in the metallic form in the shape of fillings, or in the form of a carbonate, sulphuret, sulphate, or sulphide, or oxide, as may be most convenient.

The substance produced in this manner possesses the property of emitting light in the dark in a very high degree. An exposure to light of very short duration, sometimes but for a moment, will cause the substance to become luminous and to remain in this luminous condition, under favorable circumstances, for upward of twenty-four hours.

The intensity of the light emitted by this composition after exposure is considerable, and largely greater than the light produced by any of the substances heretofore known.

The hereinbefore described substance may be ground with oil and used like ordinary paint; or it may be ground with any suitable varnish or be mixed in the manner of water colors; or it may be employed in any other suitable and well-known manner in which paints are employed.

My improved luminous substance is adapted for a great variety of uses--for instance, for painting business and other signs, guide boards, clock and watch dials, for making the numbers on houses and railway cars, and for painting all surfaces which are exposed periodically to direct or indirect light and desired to be easily seen during the night.

When applied with oil or varnish, my improved luminous substance can be exposed to the weather in the same manner as ordinary paint without suffering any diminution of its luminous property. I claim as my invention the herein described luminous substance, consisting of calcined chalk, sulphur, and bismuth, substantially as set forth.

Merrill B. Sherwood, Jr., of Buffalo, N. Y., obtained a patent for a phosphorescent composition, dated August 9, 1881.

The author says: My invention relates to an improvement in phosphorescent illuminants.

I have taken advantage of the peculiar property which obtains in many bodies of absorbing light during the day and emitting it during the night time.

The object of my invention is the preparation by a prescribed formula, to be hereinafter given, of a composition embodying one of the well-known phosphorescent substances above referred to, which will be applicable to many practical uses.

With this end in view my invention consists in a phosphorescent composition in which the chief illuminating element is monosulphide of calcium.

The composition obtained by the formula may be used either in a powdered condition by dusting it over articles previously coated, in whole or in part, with an adhesive substance, or it may be intimately mixed with paints, inks, or varnishes, serving as vehicles for its application, and in this way be applied to bodies to render them luminous.

The formula for obtaining the composition is as follows: To one hundred parts of unslaked lime, that obtained from calcined oyster shells producing the best results, add five parts of carbonate of magnesia and five parts of ground silex. Introduce these elements into a graphite or fire-clay crucible containing forty parts of sulphur and twenty-five parts of charcoal, raise the whole mass nearly or quite to a white heat, remove from the fire, allow it to cool slowly, and, when it is cold or sufficiently lowered in temperature to be conveniently handled, remove it from the crucible and grind it. The method of reducing the composition will depend upon the mode of its use. If it is to be applied as a loose powder by the dusting process, it should be simply ground dry; but if it is to be mixed with paint or other similar substance, it should be ground with linseed or other suitable oil. In heating the elements aforesaid, certain chemical combinations will have taken place, and monosulphide of calcium, combined with carbonate of lime, magnesia, and silex, will be the result of such ignition.

If, in the firing of the elements, as above set forth, all of the charcoal does not unite with the other elements, such uncombined portion should be removed from the fused mass before it is ground.

If it is designed to mix the composition with paints, those composed of zinc-white and baryta should be chosen in preference to those composed of white lead and colored by vegetable matter, as chemical action will take place between the composition and paint last mentioned, and its color will be destroyed or changed by the gradual action of the sulphureted hydrogen produced. However, by the addition of a weak solution of gum in alcohol or other suitable sizing to the composition, it may be used with paints containing elements sensitive to sulphureted hydrogen without danger of decomposing them and destroying their color.

In many, and possibly in a majority of cases, the illuminating composition applied as a dry powder will give the most satisfactory results, in view of the tendency to chemical action between the paint and composition when intimately mixed; in view of the fact that by the addition to paint of any color of a sufficient quantity of the composition to render the product luminous, the original color of the paint will be modified or destroyed; and, also, in view of the fact that the illuminating composition is so greatly in excess of the paint, the proportions in which they are united being substantially ten parts of the former to one of the latter, it will be difficult to impart a particular color to the product of the union without detracting from its luminosity. On the other hand, the union of dry powder with a body already painted by the simple force of adhesion does not establish a sufficiently intimate relation between it and the paint to cause chemical action, the application of a light coat of powder does not materially change the color of the article to which it is applied; and, further, by the use of the powder in an uncombined state its greatest illuminating effects are obtained. Again, if the appearance in the daytime of the article which it is desired to have appear luminous at night is not material, it may be left unpainted and simply sized to retain the powder.

In printing it is probable that the composition will be employed almost exclusively in the form of dry powder, as printing-ink, normally pasty, becomes too thick to be well handled when it is combined with powder in sufficient quantity to render the printed surface luminous. However, the printed surface of a freshly printed sheet may be rendered luminous by dusting the sheet with powder, which will adhere to all of the inked and may be easily shaken from the unmoistened surfaces thereof.

I am aware that monosulphide of calcium and magnesia have before been used together in phosphorescent compounds. What I claim is a phosphorescent composition consisting of monosulphide of calcium, combined with carbonate of lime, magnesia, and silex, substantially as described.

Orlando Thowless, of Newark, N.J., obtained a patent for a process of manufacturing phosphorescent substances dated November 8, 1881. The inventor says: The object of my invention is to manufacture phosphorescent materials of intense luminosity at low cost and little loss of materials.

I first take clam shells and, after cleaning, place them in a solution composed of about one part of commercial nitric acid and three parts of water, in which the shells are allowed to remain about twenty minutes. The shells are then to be well rinsed in water, placed in a crucible, and heated to a red heat for about four hours. They are then removed and placed, while still red-hot, in a saturated solution of sea salt, from which they are immediately removed and dried. After this treatment and exposure to light the shells will have a blood-red luminous appearance in the dark. The shells thus prepared are used with sulphur and the phosphide and sulphide of calcium to produce a phosphorescent composition, as follows: One hundred parts, by weight, of the shells, prepared as above, are intimately mixed with twenty parts, by weight, of sulphur. This mixture is placed in a crucible or retort and heated to a white heat for four or five hours, when it is to be removed and forty parts more of sulphur, one and one-half parts of calcium phosphide, and one-half part of chemically pure sulphide of calcium added. The mixture is then heated for about ninety minutes to an extreme white heat. When cold, and after exposure to light, this mixture will become luminous. Instead of these two ignitions, the same object may be in a measure accomplished by the addition of the full amount of sulphur with the phosphide and sulphide of calcium and raising it to a white heat but once. The calcium phosphide is prepared by igniting phosphorus in connection with newly slaked lime made chemically pure by calcination. The condition of the shells when the sulphur is added is not material; but the heat renders them porous and without moisture, so that they will absorb the salt to as great an extent as possible. Where calcined shells are mixed with solid salt, the absorbing power of the shells is greatly diminished by the necessary exposure, and there will be a lack of uniformity in the saturation. On the contrary, by plunging the red-hot shells in the saline solution the greatest uniformity is attained.

Instead of using clam shells as the base of my improved composition, I may use other forms of sea shells--such as oyster shells, etc.

I claim as new:

1. The herein described process of manufacturing phosphorescent materials, which consists in heating sea shells red-hot, treating them while heated with a bath of brine, then, after removal from the bath, mixing sulphur and phosphide and sulphide of calcium therewith, and finally subjecting the mixture to a white heat, substantially as and for the purpose described.

2. The described process, which consists in placing clean and red-hot clam shells in a saturated solution of sea salt, and then drying them, for the purpose specified.

* * * * *

BOXWOOD AND ITS SUBSTITUTES.

[Footnote: Prize essay written for the International Forestry Exhibition, Edinburgh.]

By JOHN R. JACKSON. A.L.S., Curator of the Museums, Royal Gardens, Ken.

The importance of the discovery of a hard, compact, and even grained wood, having all the characteristics of boxwood, and for which it would form an efficient substitute, cannot be overestimated; and if such a discovery should be one of the results of the present Forestry Exhibition, one of its aims will have been fulfilled.

For several years past the gradual diminution in the supplies of boxwood, and the deterioration in its quality, have occupied the attention of hardwood merchants, of engravers, and of scientific men.

Of merchants, because of the difficulties in obtaining supplies to meet the ever increasing demand; of engravers, because of the higher prices asked for the wood, and the difficulty of securing wood of good size and firm texture, so that the artistic excellence of the engraving might be maintained; and of the man of science, who was specially interested in the preservation of the indigenous boxwood forests, and in the utilization of other woods, natives, it might be, of far distant countries, whose adaptation would open not only a new source of revenue, but would also be the means of relieving the strain upon existing boxwood forests.

While by far the most important use of boxwood is for engraving purposes, it must be borne in mind that the wood is also applied to numerous other uses, such, for instance, as weaving shuttles, for mathematical instruments, turnery purposes, carving, and for various ornamental articles, as well as for inlaying in cabinet work. The question, therefore, of finding suitable substitutes for boxwood divides itself into two branches, first, directly for engraving purposes, and, secondly, to supply its place for the other uses to which it is now put. This, to a certain extent, might set free some of the boxwood so used, and leave it available for the higher purposes of art. At the same time, it must not be forgotten that much of the wood used for general purposes is unsuited for engraving, and can only therefore be used by the turner or cabinet maker. Nevertheless, the application of woods other than box for purposes for which that wood is now used would tend to lessen the demand for box, and thus might have an effect in lowering the price.

So far back as 1875 a real uneasiness began to be felt as to the future supplies of box. In the _Gardeners' Chronicle_ for September 25, of that year, page 398, it is said that the boxwood forests of Mingrelia in the Caucasian range were almost exhausted. Old forests, long abandoned, were even then explored in search of trees that might have escaped the notice of former proprietors, and wood that was rejected by them was, in 1875, eagerly purchased at high prices for England. The export of wood was at that time prohibited from Abhasia and all the government forests in the Caucasus. A report, dated at about the same period from Trebizond, points out that the Porte had prohibited the cutting of boxwood in the crown forests. (_Gardeners' Chronicle_, Aug. 19, 1876, p. 239.) Later on, the British Consul at Tiflis says: "_Bona fide_ Caucasian boxwood may be said to be commercially non-existent, almost every marketable tree having been exported." (_Gardeners' Chronicle_, Dec. 6, 1879, p. 726.)

The characters of boxwood are so marked and so distinct from those of most other woods that some extracts from a report of Messrs. J. Gardner & Sons, of London and Liverpool, addressed to the Inspector-General of Forests in India, bearing on this subject, will not be without value; indeed, its more general circulation than its reprint in Mr. J.S. Gamble's "Manual of Indian Timbers" will, it is hoped, be the means of directing attention to this very important matter, and by pointing out the characters that make boxwood so valuable, may be the means of directing observation to the detection of similar characters in other woods. Messrs. Gardner say:

"The most suitable texture of wood will be found growing upon the sides of mountains. If grown in the plains the growth is usually too quick, and consequently the grain is too coarse, the wood of best texture being of slow growth, and very fine in the grain.

"It should be cut down in the winter, and, if possible, stored at once in airy wooden sheds well protected from sun and rain, and not to have too much air through the sides of the sheds, more especially for the wood under four inches diameter.

"The boxwood also must not be piled upon the ground, but be well skidded under, so as to be kept quite free from the effects of any damp from the soil.

"After the trees are cut down, the longer they are exposed the more danger is there afterward of the wood splitting more than is absolutely necessary during the necessary seasoning before shipment to this country.

"If shipped green, there is great danger of the wood sweating and becoming mildewed during transit, which causes the wood afterward to dry light and of a defective color, and in fact rendering it of little value for commercial purposes.

"There is no occasion to strip the bark off or to put cowdung or anything else upon the ends of the pieces to prevent their splitting.

"Boxwood is the nearest approach to ivory of any wood known, and will, therefore, probably gradually increase in value, as it, as well as ivory, becomes scarcer. It is now used very considerably in manufacturing concerns, but on account of its gradual advance in price during the past few years, cheaper woods are in some instances being substituted.

"Small wood under four inches is used principally by flax spinners for rollers, and by turners for various purposes, rollers for rink skates, etc., etc., and if free from splits, is of equal value with the larger wood. It is imported here as small as one a half inches in diameter, but the most useful sizes are from 21/2 to 31/2 inches, and would therefore, we suppose, be from fifteen to thirty or forty years in growing, while larger wood would require fifty years and upward at least, perhaps we ought to say one hundred years and upward. It is used principally for shuttles, for weaving silk, linen, and cotton, and also for rule making and wood engraving. _Punch, The Illustrated London News, The Graphic_, and all the first class pictorial papers use large quantities of boxwood."

In 1880, Messrs. Churchill and Sim reported favorably on some consignments of Indian boxwood, concluding with the remarks that if the wood could be regularly placed on the market at a moderate figure, there was no reason why a trade should not be developed in it. Notwithstanding these prospects, which seemed promising in 1877 and 1880, little or nothing has been accually done up to the present time in bringing Indian boxwood into general use, in consequence, as Mr. Gamble shows, of the cost of transit through India. The necessity, therefore, of the discovery of some wood akin to box is even more important now than ever it was.

BOXWOOD SUBSTITUTES.