Glass and Glass Ware, Paris 1878 - 10




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Many beautiful things were exhibited in Paris which, I fear, leave us far behind in the race of human competition. The artistic skill displayed by the European manufacturers is in marked contrast with our home productions. I refer more particularly to articles of luxury.

In designs we are sadly behindhand. France and Bohemia are in the van. England, although manufacturing beautiful wares, so far as workmanship is concerned, is occasionally wofully behind in designs. It is a pity to see beautiful brilliant glass engraved with the greatest skill and art — display of uncommon talent — wasted upon ugly mugs or jugs.

The variety of colored glass made in Europe is really surprising. Different colored glasses are combined together in beautiful harmony, pleasing to the eye. In flint glass, which after all is the king of glass, the perfection of the cut and engraved glass is all that could be desired. Nothing is prettier than a beautiful transparent vase made of brilliant flint glass cut in deep patterns, such as flutes, diamonds, or other figures. This can only be excelled, perhaps, by the beautiful and artistically engraved pieces which were displayed at the Exposition in the British and Bohemian departments. In antique glass we find many beautiful specimens of workmanship, but, in my opinion, we have yet to see anything excelling some of our modern productions. I certainly think that we have but little, if anything, to copy from the antique wares, and am in the number of those who believe that to lament over the lost arts, as it is somewhat fashionable to do, is simply to make an exhibit of ignorance or weakness. The glass industry of the present day is as far advanced as history has ever shown it to have been, with, perhaps, a very few unimportant exceptions.

The manufacture of table and ornamental wares is divided into two branches, flint-glass and lime-glass.

Flint glass is known by the English as a glass containing lead. The French and Belgians call it “crystal,” but the Germans call indistinctly all white glass “crystal,” whether lead enters into it or not. It would be quite desirable to have different kinds of glass designated by names conveying a meaning of their nature and composition. In this country we are laboring under the same difficulties, and glass containing small proportions of lead or none at all is often called “crystal glass.” The equivalent of the “white glass” of Europe we designate under the name of “lime glass.”

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European “white glass,” although made beautifully transparent, free from coloring tints to a great degree, never can attain the brilliancy of flint glass. The Bohemians and Germans, who excel in the making of lime glass, treat it in its decoration precisely as the English, French, and Belgians do with flint. Light not being reflected with that brilliancy so strikingly noticeable in flint, this glass always has a bluish-gray tint, which detracts materially from its beauty.

We owe the invention of flint glass to the English. Wood was used as a fuel in the beginning of glass making, but it having become scarce in England coal was resorted to as a substitute. This fuel, however, producing a great quantity of smoke in the furnace, many impurities were mixed with the glass and gave it a coloring. To obviate this difficulty, pots, which had been made heretofore without covers, were now covered. This, however, reduced the temperature of the contents of the pots, and it was found that glass made with the ordinary mixtures was too hard to melt. Red lead was then introduced as a flux; this remedied the difficulty. To this day the English retain the supremacy in the manufacture of flint glass; in color, brilliancy, and superior purity of metal, it is not surpassed by any other country. France and Belgium are also making large quantities of flint-glass wares, and I particularly noticed that since 1867 French flint had been materially improved. The peculiar grayish tint which distinguished the French from the English then has now disappeared, and French flint is nearly equal to the English.

Belgium has somewhat departed from the manufacture of pure flint glass, and to meet the demand for cheap wares has been making ordinary white glass with a small proportion of lead added. The manufacture of flint glass in Belgium, at the present day, amounts to $1,600,000. In 1876 the exportation amounted to $340,000.

The materials used in flint-glass making are potash, red lead, sand, and small proportions of oxide of manganese as a corrector of color.

Potash is used in the form of carbonate, and should be as free as possible from sulphate, chlorate, soda salts, iron, and organic matters. Sometimes 10 to 20 per cent. of niter is substituted for soda, giving a very fine glass. Its use, however, is somewhat objectionable, as it destroys pots very rapidly; its high-cost price is another objection. The English use potash coming from America; it is refined by manufacturers, who sell the purified article direct to the glass-makers. France draws her potash from America, Tuscany,

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and Germany. The potash contained in the residuum of the beet-root sugar-making is also used.

Red lead. — The selection of leads for making red lead should be very particular; the metal should be free from copper, iron, and even silver. Zinc and antimony are less troublesome. In the large establishments of France red lead is generally made on the premises. The best lead is drawn from Spain. Germany has also a few superior brands.

As many manufacturers cannot afford to manufacture their own red lead, and are obliged to purchase it from the trade, I will briefly show how the presence of copper can be detected.

Take a determined quantity of red lead, say 50 grams; add, say, 50 centimeters of concentrated ammonia. The bottle should be big enough to contain about 200 cubic centimeters; shake now and then. In a few days if a blue coloration should take place it is an indication of the presence of copper; the deeper the color the larger the quantity. Litharge may be treated in the same manner. If red lead or litharge give a decided blue tint to glass, they must be rejected as containing iron. The use of litharge has often been tried instead of red lead, but the result has never been satisfactory, and always produces a glass of inferior quality.

Cullets or broken glass. — The glass remaining upon the blow-pipes after an article has been blown is saved for use over again. This glass contains oxide of iron detached from the pipes in cleaning them; since it would be quite unfit for use in this state, it is necessary to eliminate the iron. For this purpose the following process is employed: Diluted sulphuric acid is introduced into large iron boxes lined with lead and heated to 180 degrees Fah. The liquid should be stirred now and then. Twelve hours or more afterwards the iron is nearly all dissolved; the cullets should then be taken up, washed, and dried.

Sand. — The sand used in flint-glass making should be of the greatest purity, and if it contains iron the same treatment as indicated for cleaning cullets is resorted to with very good effect. In all cases, however, sand should be washed in water before using it.

Flint glass in Europe is generally made with the following mixture:

Silica (sand) 100
Red lead 66 2/3
Carbonate of potash 33 1/3
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This proportion is usually followed by all manufacturers. It shows: 1 part carbonate of potash; 2 parts red lead; 3 parts sand. It is seldom deviated from and produces a very good metal. To correct the color small proportions of oxide of manganese are sometimes added. To the above mixture a quantity of cullets should be added at least equal to the weight of the sand.

Other materials have been tried in making flint glass. Boracic acid has been used by MM. Maës and Clémandot, of Clichy, near Paris. By the use of this flux the composition of glass can be greatly modified; oxide of zinc may take the place of red lead; lime, soda, or barytes may be used instead of potash. These substitutions, in connection with boracic acid, have produced a beautiful glass, suitable for table ware or optical purposes, which is remarkable for limpidity, whiteness, and brilliancy. The furnaces used are of the direct-fire style, containing 8 to 10 pots of a capacity of about 600 pounds, heated by wood or coal. As wood has become quite scarce in many localities, coal is gradually being substituted. The direct-fire furnaces are also gradually passing away, and the Siemens and Boëtius gas furnaces are taking their places. Economy of fuel with European manufacturers is a question of more importance than with us. With abundance of fuel in this country, we have not felt the necessity of economy to such a degree as they have. Gas furnaces possess so many advantages that their use should be generally adopted; those burning coal can now be run with open instead of closed pots. Mr. Didierjean, of the Saint Louis Glass Works succeeded in so directing a mixture of gas and air in suitable proportions and directions that the former oxidation of glass in open pots is now avoided.

In the ordinary furnaces eight or nine hours are necessary to melt glass, the refining taking about one or two hours more. The blowers work for eleven hours, with half an hour’s rest at noon. Work begins and ends every day at the same hours, from 5 a. m. to 4 p. m., continuing for six days every week.

In England the custom is entirely different. The furnaces and pots are very large; the pots contain as much as 2,000 pounds, and require from forty-eight to sixty hours’ firing before melting. The glass being melted, work is continuous day and night without intermission for four or four and a half days, until the glass is all worked up. This does not appear to be a wise method of working. The glass remaining so long melted in the pots is apt to lose its good quality and homogeneousness, also causing striae to appear

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towards the end, sometimes ending in devitrification. Each set of workmen in France is composed of twelve persons, while in England there are only four, viz: a finisher, a gatherer, a blower, and a boy. As the latter mode of working must necessarily occupy a large part of the high-priced workmen in doing the work that could be performed by cheaper hands and by subdividing the labor, it does not seem to me to be as economical as the French mode.

The English method, however, has some advantages. As the furnaces are kept at a low heat for long periods while working, this naturally increases the life of the furnaces. While the French furnaces rarely last over one year or eighteen months, and the pots from six weeks to two months, the English frequently preserve their furnaces from six to eight years, provided the benches are repaired every two years; the pots last on an average from four to six and sometimes seven months. The frequent alternate cooling and heating of the French furnaces causes them to disintegrate much more rapidly than the English. The English method, however, requires a larger quantity of coal, but with their cheap coals this does not weigh much in a question of general economy.

The leer or annealing oven does not differ from those used in this country. It is the usual long furnace, heated in front with two fire-places, the flame striking against the arched top and reverberating the heat upon the wares placed in iron pans traveling on rails.

The “glory-hole” or reheating furnace is also of the ordinary style found in this country.

The tools are of the usual kind, and but little novelty is found in them. Foreign manufacturers have not become so familiarized with mechanical appliances as we have in this country. The American pressed glass, which I sent for and exhibited myself, at my own expense, drew from the European manufacturers exclamations of astonishment when they saw the clearness, smoothness, and brilliancy of this glass, the freedom from mold-marks, and the superior execution in general. Frequent inquiries were made as to the mode of working. This was a positive proof that they consider us superior in that line. In fact, many manufacturers frankly acknowledged to me our uncontested superiority in pressed glass. Nothing could be seen elsewhere in the Exposition equaling our samples.

As a great many wares are still blown simply with the few tools of the craft, the foreign workman as a general thing is well skilled and superior to his American brother.

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To illustrate how few new introductions have been made in the glass-blower’s tools, I have been told that the use of “snaps” to hold pieces while reheating is of recent origin in Europe, as is also the use of a whole iron mold for bottles, instead of the half mold, which had been used for many years.

I wish to recommend to our manufacturers the use of wooden molds, knowing how in France, Belgium, and Bohemia these molds have been the means of cheapening production and insuring regularity. There are scarcely any blown articles made without the help of these molds. They are cheap, and, where a very large quantity of pieces is not wanted, they are the best kind of molds yet found to produce clear, smooth wares. For the making of current articles, needed in great quantities, wooden molds do not answer as well, as they do not hold their outlines sharp long enough, owing to the slow burning or charring of the inside. To avoid this difficulty iron molds have been used; they are lubricated with a fatty or resinous substance, which is occasionally renewed. The same clearness of glass cannot be obtained, however, as with wooden molds. In the Bohemian exhibits I saw a quantity of beautiful vases and other articles which I was told had been blown in wooden molds. These wares are very regular and beautiful in shape.

A new practice has recently been introduced in France, to which I also wish to call the attention of our glass-makers. It is the invention of M. Clémandot, a celebrated and competent glass manufacturer. I refer to the coating with nickel of molds, blow-pipes, and tools used in glass-blowing. This coating prevents the oxide of iron from being introduced into glass through impure cullets. This process has been applied with success in several glass works, and I should like to see it tried here. A coating of nickel is readily imparted by immersing the objects in a plating bath of sulphate of nickel and ammonia for several hours.

I shall not undertake to describe the blowing processes for table and other wares but very briefly. It is the skill of the workmen which secures the reputation of glass works in Europe, since mechanical means are but little known or used. The process of blowing consists in dipping a metallic “blow-pipe” into the mass of glass contained in the pot. The blow-pipe being colder than the glass, the latter adheres firmly to it, and, owing to the cooling action of the ambient air, gradually becomes solidified, but it should be worked

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while yet plastic. The workman now blows through the pipe and gradually forms a hollow ball, which, by means of his few simple tools, he brings to the proper shape so as to form the desired article. The tools of the glass-blower are but few; they are the blow-pipe, pinchers, shears, calipers, a marver or iron plate, a bench, and a few other primitive so-called tools.

The so-called “doubled glass,” known as “flashed glass” in this country, is a glass made of several colors superposed. It is worked in a different manner from plain glass. Colored glass when first made is generally drawn into sticks of a certain length and annealed. Suppose we now wish to blow an article made of white glass with a thin sheet of outside colored glass. A stick of colored glass is taken and heated gradually; the workman now takes up this stick on the end of his “ponty” — an iron rod upon which a little hot glass has been gathered — and heats the glass in the “glory-hole.” When this is sufficiently plastic a quantity is cut off and attached to a blow-pipe also having a small lump of hot glass at its end. The colored lump is now heated again and blown in the usual way into a hollow ball. This ball is opened and formed into the shape of a cup. In the mean time another workman has gathered and blown another sphere of white glass of a suitable size. This sphere is now put into the cup-shaped colored glass, blown, and rubbed together while hot so as to make them adhere. We now have a ball of white glass inside and colored glass outside. This may be finished to any shape desired, in the usual way, with molds or tools.

The variety of articles made in glass is so great that I cannot possibly describe the different processes. It is not thought to be within the scope of such report as this to give detailed descriptions. I wish, however, to impress on the minds of our manufacturers the necessity, growing more every day, of traveling out of the now beaten path of ordinary goods, and taking up the making of the beautiful fancy articles which were to be seen in such profusion in the Exhibition. We are sadly behind the times in these wares; we are at the head in pressed glass, why should we not strive also to reach that position in fancy wares? Our deficiency is particularly striking in the making of doubled, trebled, and quadrupled colored glass; the blowing of solid ribbed vases; in articles having cameos on the surface; vases blown of two colored glasses, with relief designs, which are subsequently cut away in alternate places so as to show faces of different colored glass; mottled colored

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glass, imitating marble; the blowing of minute hollow tubes between two layers of glass ; the spinning of colored glass threads upon the surface of articles; and the endless variety of Venetian fancy goods. The same may be said of bronzed and white iridescent glass, the yellow and green aventurine, etc. I notice, however, of late, a tendency to introduce colored glass by our manufacturers, and I have already seen very handsome articles made of solid colored glass.

Cutting and engraving are two processes very similar. The cutting or grinding of glass is usually done with four kinds of grinding wheels or disks, revolved by power: (1) a cast or wrought iron wheel; (2) a stone wheel of very close grain; (3) a wooden wheel; and (4) a cork wheel. The operation is briefly as follows: The iron wheel, being mounted upon a suitable frame, is made to revolve; over the wheel a hopper, containing sand and water, is hung, the wet sand falling on the periphery of the wheel. The piece of glass being held against the face of the wheel, the sand, by its abrading action, grinds away the glass. The next operation is to take the ground object, which now presents a very rough surface, and apply it against the revolving stone wheel, kept moist by a stream of water running out of the hopper. This operation removes the asperities produced by the first operation, but this does not restore the former brilliancy of the glass. To partially produce this polish the glass is next held against a revolving wooden wheel, usually of poplar or willow. A wet pumice-stone powder is occasionally spread over the wheel. The glass is now quite smooth and free from scratches, but is not sufficiently polished. The cork wheel is now used for the last operation; it is sprinkled over with “tin putty” or colcothar. The polishing action of the cork wheel completely restores to the glass the polish and brilliancy which it originally possessed.

To cut glass with such a scantiness of mechanical means, it will be seen readily, necessitates a long practice and skill in the workmen, as they have nothing but the eye to depend upon for guidance. Nevertheless, with such limited means, the most beautiful designs are cut with wonderful effect. But upon a close examination the work is often found very irregular. When the operation has to be repeated over again, and the same patterns have to be cut, it is exceedingly difficult to obtain regularity in the work, and to make the pieces alike. In pressing glass in molds having the shape and design desired, the operation being entirely mechanical, and consequently accurate, it is an easy matter to produce a large number of pieces perfectly alike. Pressed

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glass, however, never can attain the beauty and perfection of cut glass. The molds cannot produce the outlines and angles sharp enough, and should they be produced in pressing they would be blunted in reheating or fire-polishing. Cut and pressed glass will, therefore, each maintain its respective sphere.

Several attempts have been made to cut glass by machinery, but until recently they have met with poor success. In France a machine has just been brought out for cutting several tumblers at a time. This machine was in operation at the Exhibition, but showing only the cutting of one glass at a time. Since the inventor called it an experimental machine only, not completed, I could not judge of its merits or of the improvements he contemplates making. As I saw the machine in operation, however, I do not think it will ever realize the sanguine expectations of the inventor. The tumbler is mounted upon a holder, pressing upon the face of a horizontally revolving wheel; the holder is weighted sufficiently to give the proper pressure to grind out the flutes. The machine is automatic, raising and revolving the tumbler a sufficient distance to cut the next flute and again lowering it against the grinding wheel. The operation is repeated until all the flutes around the tumbler are cut.

Another glass-cutting machine has been introduced in Germany, but since the German Government did not take part in the Exhibition, except in the fine arts, I had no opportunity of seeing it in operation. From an examination of the drawings which I saw I am inclined to think that the same defects exist in this as are to be found in the French machine; neither of them regulate the penetration of the grinding wheel, and simply depend upon pressure for action. This German machine, however, seems to be adapted to a greater variety of work than the French.

In the American section samples of glass cut by machinery were exhibited by Mr. J. P. Colné, the result of a joint invention with the writer. These were the only machine-cut articles in the Exhibition, and excited the curiosity of the foreign manufacturers, owing to the beauty and regularity of the work. These samples consisted of decanters, goblets, sugar bowls, mustard pots, tumblers, etc., of different shapes and styles of cutting. The machine was not on exhibition, but it has since been put in operation very successfully in France by the inventors. It is not entirely automatic, but is adapted to cut all geometrical

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shapes and patterns, as well as a great variety of styles of cutting, and does not require any skill in the person working it, as the penetration is perfectly regulated. The rapidity, the regularity, and the perfection of the work done with this machine insures a great saving in the original cost price of cut articles.

In glass-cutting, as in other branches of the glass manufacture, I recommend the use of mechanical means to cheapen and perfect the production of wares. We have seen the benefits of machinery in the ingenious inventions of molds and presses now so extensively worked in our establishments. Machinery for cutting glass must necessarily work the same results.

Engraving glass is a similar process to cutting, the difference being in the tools. In engraving, instead of using a large iron wheel with sand and water, a very small copper disk with emery and oil are used. To engrave glass requires very skillful workmen. The work produced by Bohemian and English engravers is truly wonderful. France and Belgium also produce very fine work, but the artists, or at least many of them, are of Bohemian origin.

Etching in clear and dead white grounds by means of hydrofluoric acid has been carried to a great state of perfection in Europe, particularly in France. This comparatively new process of engraving is capable of producing beautiful work at a greatly reduced price. By means of properly prepared designs with the well-known printing processes on paper, the most intricate and beautiful patterns may be etched upon glass with great perfection. Of late years the dead-white etching upon clear glass has been carried to a high degree of success in France; in fact, it can be said that from the time this style of ornamenting glass was discovered dates the successful introduction of etching on glass.

The sand-blast process has quite recently been introduced into England and Belgium, but, so far, has taken no footing in France, with the exception of one establishment, which is preparing, and may by this time have made an experimental trial. I think that so valuable an invention must make its way even against the competition of etching by acid. In this country this style of engraving has proved quite a success on flat surfaces or sheet-glass; I wish we could see it applied more generally to our table and fancy wares, lamps, and gas globes. I have already seen some very fair applications of sand engraving to ornamenting shades, globes, etc. Sand engraving in combination with

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enamel painting would produce very pretty effects, and I hope to see it tried by some of our glass-makers.

Lime or white glass. — The center of manufacture of this glass is in Germany. Bohemia is especially famous for its “white glass.” The Bohemians make in this glass all articles made elsewhere in flint; in fact, they blow it and decorate it precisely in the same manner. The Bohemian display of fancy colored, highly decorated, cut, engraved, and painted glass was truly beautiful. The color of their “white glass,” however pure the materials may have been, and however carefully it may have been made, never reaches the brilliancy and limpidity of flint-glass. Bohemian white glass being much harder than flint, it requires to be worked promptly, since it cannot stand reheating as well as lead-glass. This peculiarity has led Bohemians to adopt a special system or method of blowing. To avoid frequent reheating, articles are blown at one or at as few operations as possible. For this purpose wooden molds almost exclusively are used, so that one blowing is sufficient to give the required shape. This, to a great measure, cheapens their productions, but these molds are of especial advantage in giving to their wares the beautiful shapes we are accustomed to see in their fancy vases. Although labor is very cheap in Bohemia, I doubt whether skilled labor could be procured at the low prices usually paid were these pieces to be blown by hand instead of the wooden molds. England to this day refuses, or rather the workmen do, to use any wooden molds. Any attempt to introduce these molds would be followed at once by a strike in that unfortunate strike-ridden country. It is true, I have seen very regularly blown wares coming from England, but they must be the work of highly-skilled workmen, who must naturally be but few and well paid. Wooden molds, formerly a secret to the French manufacturer, are now used very extensively.

Articles blown in wooden molds are sometimes opened with shears and finished before being annealed, but the great mass of them are sent to the leer without being opened. The operation of cutting open is done with curved hot irons of about the same diameter as the piece, which are held against it while it is being revolved. This produces a slightly heated ring, and, as glass is a bad conductor of heat, the heated circle does not extend to the mass. By wetting the heated circle a rupture takes place and extends all the way around the piece. A slight blow detaches the top, leaving the object opened. The edge, which is left angular

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and cutting, is smoothed and finished by grinding and polishing.

Bohemian manufacturers work in a very primitive manner. The glass-houses are generally built in the midst of forests, made of very rude frame buildings. The furnaces are very small, burn wood, and contain only seven or eight very small pots. Glass-making in Bohemia is divided into two distinct branches: The glass-blowers who generally manufacture the rough, unfinished articles, and the glass-refiners, so called, who cut, engrave, and decorate them in their various well-known and skillful ways. A few factories do the whole work in the same establishment; the larger number simply blow or mold articles and sell them to the glass-refiners. Since these factories burn wood, the furnaces are generally placed in the midst of timber, and as the fuel recedes from the factories, it is found more economical to move the furnace than to bring the fuel to it. Furnaces are therefore very unstable affairs. This state of affairs prevents owners of glass works from carrying on the decoration and finishing of glass in the neighborhood of the furnaces, since for this purpose more substantial buildings are required. Thus gradually the so-called glass refining became separated from the blowing and became an entirely separate branch. The statistics published in the Austro-Hungarian catalogue of the Exposition show that in 1876 there were 177 glass-houses, with 273 furnaces and 1,663 pots, employing 7,100 workmen. As I have already stated, wood is the principal fuel; 47 establishments, however, burn coal, 7 are run with wood and coal, 6 with wood and peat, and 117 use wood exclusively. These fuels are used in direct-fire furnaces, or are first distilled into gases and burned in gas furnaces. Quartz used in making glass is found in abundance in the vicinage of the works. Chemicals employed are generally procured from the chemical works of the country. Soda is procured from abroad. Of late years carbonate of soda has taken the place of potash, generally used by the Bohemians; owing to its lower price, it is gradually introduced into all the different kinds of glass they make. Recently, however, sulphate of soda, being still cheaper, is taking the place of the carbonate.

There are 63 window-glass works in Austria making cylinder glass, 46 making cast glass, and 50 making both; 12 make drawn glass, made into tubes, sticks, drops, spun glass, etc. Most of the works are situated in Bohemia. In the Bohmerwald district wood is used as fuel, but in North Bohemia coal takes its place. The “glass refineries” are found in

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the districts of Haida and Gablonz, where the workmen mostly work at home. The finishing of plate-glass is carried on in the Pelsen district, where 44 establishments are to be found for grinding and finishing, and 8 for silvering. The pressed, cat, and spun glass factories are situated in the district of Gablonz and Tannwald, in North Bohemia. In the township of Rechenberg 2,222 establishments are to be found, some of them, however, very small. The total annual production of Austria reaches at least $12,000,000. The government encourages the glass industry by all means in its power. Museums, drawing, and art schools have been opened in several places, and a practical school was founded in 1857 in Steinschönau.

Bohemian white glass is a strong rival to flint; it is well melted, hard, homogeneous, and brilliant; it can be cut and engraved with advantage. It, however, seems to have a slight yellow or blue tinge, notwithstanding the care manufacturers take for getting rid of impurities in the materials used. This glass, containing a great percentage of silica, is very hard and well calculated to stand the fire of the muffle in decorating it. It also resists very well the action of chemicals, and is invaluable in the laboratory.

Bohemians excel in making colored pot-metal or glass colored in the mass. The larger number of colors now made have been discovered by them. They are excellent engravers, and whenever very fine engraving is found it is generally the work of a Bohemian or of a descendant of that country. Sand is seldom used, but quartz is quite abundant and is substituted for it. It is prepared by heating it and throwing it into cold water, then pulverized in mills. Lime is found in profusion in the country.

The average Bohemian glass contains the following proportions:

Pulverized quartz 100
Carbonate of potash 28 to 32
Slacked lime 13 to 15
Oxide of manganese 1
Arsenic 3

Sometimes a few hundredths of saltpeter, borax, and red lead are added.

Bohemian furnaces are elliptical in form the pots do not hold more than 160 pounds of mixture, requiring at least eighteen hours to melt. At the side and above the furnace is built a chamber to receive the waste heat escaping from the combustion. This chamber is used for annealing finished wares, heating quartz, and burning lime. When

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wood is used as a fuel a third chamber is built on top of the latter, and is used for drying wood and preparing it for fuel. There are only five working days per week in Bohemian factories.

Belgium, a country having a high reputation for glass-making, does not follow the Bohemian system, but manufactures for common table wares a half-flint glass. This glass, however, lacks the beauty of white lime glass of Bohemia; it is of a grayish-blue color, which is not pleasant to the eye.

Belgium, in 1867, exported $146,000 worth of lime or white glass; in 1876 the importation had increased to $670,000.

The French make a white or lime glass somewhat with the same materials as the Bohemians. The use of sulphate of soda of late has cheapened this glass materially, and the goods produced are comparatively good. The lime or white glass of the French is called sometimes half-crystal. It is usually made in the following proportions:

Sand 200
Carbonate of soda 66
Lime 50
    Or, sometimes,
Sand 300
Sulphate of soda 170
Slacked lime 75
Ground charcoal 10

Sometimes a few hundredths of red lead are added to render the glass more fusible and brilliant. If potash were as cheap as soda it would be preferable for making glass, and would give a better color to it. I am not aware that England works any lime glass. Although I made repeated inquiries, verbally and in writing, I found great difficulty in obtaining information in regard to the status of glass manufacturing in England; nor did I find any documents which could throw any light upon it. Germany manufactures white or lime glass in great quantities, but as she was not an exhibitor in Paris I was not able to get any information in regard to this branch of her industry.

Glass from iron-furnace slag.

Although the manufacture of glass from the slag of blast furnaces may not be considered strictly as a branch of the glass manufacture, yet I have thought that a few remarks upon the subject might draw the attention of our iron and glass manufacturers, and might, perhaps, result in establishing