Part 6

Messrs. Copeland, whose father, the late alderman, was for some time in partnership with Spode, occupy, in Stoke-upon-Trent, the same establishment in which that great potter carried out his improvements. Since then, these makers have kept their rank among the principal leaders of the trade, and maintain their reputation for the excellence of their decoration and the beauty of their gilding. It was so far fortunate for Stoke that, although one of the smallest towns in the Potteries, it became the seat of the most important manufactories of china. It was in 1788 that Thomas Minton, who had been brought up as an engraver at the Caughley works, in Shropshire, and who in that capacity had been several years in the employment of Spode, founded in that town the establishment which subsequently became the property of his son, Herbert Minton. The father does not seem to have possessed these qualities which, as potter, should entitle him to a special notice; but the same cannot be said of the son, who soon after his father's death began to work in earnest to raise his manufactory to its present degree of eminence. The unceasing activity of his mind in carrying out improvements in all the branches of his trade, may be attested by one who for many years had the honour of working with him. On every matter connected with art his ideas were sound, and his natural tact rarely failed in finding out that which was most suited to the taste of his customers. His reputation, as the most advanced potter of his time, is so well established, that I am not astonished to find others claiming a share in it, asserting that it was at their suggestion, or with their assistance, that he left the old path to open the way to progress. Suggestions and advices are always freely given to a man of sociable disposition as was Herbert Minton, but he used his own judgment and discretion to test their practicability. In applying higher class of art to his productions, he had only to follow his own inclinations, guided by that care and prudence which are inseparable from good administration. He knew how to select his assistants, and was particularly fortunate in his partners, his two nephews: Michael Hollins, who, since he left the firm of Minton, is the owner of a large tile manufactory at Stoke; and Colin Minton Campbell, his pupil and heir, who, after taking an active part in all his labours, has so successfully followed the example set by his uncle, that Minton's manufactory is now the largest in existence, and turns out the greatest variety of ware. With Minton and Copeland must be associated the names of Messrs. Brown-Westhead, of Caulden Place; and outside Staffordshire, the Coalport works and the Royal manufactory at Worcester. These are the principal producers of richly decorated china, for which the demand has greatly increased during the last few years. The greatest bulk of that ware is, however, made at Longton, one of the pottery towns which has a reputation for the cheapness of its goods; but of late a decided tendency to improve their quality and prices must be noticed among the generality of its manufacturers. Several of them, like Messrs. Ainsley, Moore, Barlow, and others, are trying to raise their goods to the same level as those of Stoke. There are about thirty-five firms in the Potteries making china, most of them for the home trade, and over five times that number making earthenware. These two hundred and thirty manufactories are spread over an area of ten square miles, comprising the towns of Hanley, Burslem, Tunstall, Longton, Fenton, Shelton, and Stoke-upon-Trent, from which the electoral borough takes its name. These, which in a few years are likely to be amalgamated in a single town, form the district called the Potteries, containing already a population of 170,000 inhabitants engaged in the ceramic and iron trade. It has been remarked that since the foundation of Burslem, the mother town of the Potteries, the population of the district has doubled every twenty-five years, and it is easy to foresee the time when Stoke-upon-Trent will rank in importance with our largest commercial cities.

The export of porcelain is not large; but that of earthenware reaches one and a half million of pounds. This does not appear large compared with the enormous amount exported by the iron or the cotton trades, but it is satisfactory, if taken in combination with the quantity absorbed by the home trade, which represents quite as much. Our colonial trade with Australia, India, and British America is decidedly on the increase, and the same may be said as regards South America. On the contrary, our transactions with the Continent of Europe have a tendency to decrease, and to fluctuate in the case of the United States, a very important market, which, in time of prosperity, would take as much as 800,000_l._ of granite ware.

To meet the competition of France and Germany, on one side, and the Americans on the other, great changes have taken place in the management of our works. Several processes have been improved or simplified, and large manufactories have been built on better principles. These steps were not taken too soon; for if competition scarcely existed for our goods twenty years ago, that state of things has been much altered, and it will require a great deal of application and energy on our part, if we intend to maintain our position as the largest and best producers of pottery in the world.

It is a fact that America, which had not a single manufactory worth the name at the time of the New York Exhibition, produces now, with the assistance of British workmen, granite ware of tolerably good quality; and I have been told by an eye-witness, that no less than seventy ovens are now at work at Trenton, in New Jersey. The clays and coals used by these potters are good, and if the salaries are higher than they are in England, they find a compensation in the heavy duties which, since the war of Secession, are levied on our wares.

Our commercial intercourse with France has not much altered, and the quantity of our goods sent across the Channel may be considered small compared with the importance of this market. The French are the largest producers of hard porcelain, and they make their common earthenware quite as cheap, if not cheaper, than ours. However, if they are strong at home, they have never affected our trade abroad, except in the United States, where they send their porcelain in competition with English granite.

At the present time, the rivalry from which we have suffered most in Germany, the North of Europe, and as far as Italy, comes from a group of establishments situated in the Rhenish provinces and that neighbourhood: at Sarreguemines, Sarrelouis, Vaudrevange, Mettlach, Maestricht, and a few other places. Built in the centre of a populous district, where labour is still very cheap, their intelligent and wealthy proprietors share in each other's business, and consequently have no inducement for lowering their prices. They seem to have given a considerable portion of their time to the study of the various processes, and they have so far succeeded, that they are a great deal more independent with regard to their men than we are. Possessing these advantages, we cannot wonder, if we have not been able to keep our hold on those markets which were the nearest to them. Besides, it is plain, that the important rise which has taken place in the price of wages and fuel, and the consequent increase in the price of our wares, has acted as an encouragement to foreign production; and perhaps it may be good policy, in future, to resist any further opportunity which might offer to increase the price of our goods. It would, however, be singular if, in the course of time, England did not derive some benefit from this competition; she is used to close contest, and, everything considered, her position is an enviable one. Our home trade is excellent; and if the amount of our exports does not progress so fast as we could desire, we know that we have in our commercial fleet more facilities that any other nation for sending our goods to those numerous countries where the trade of pottery is hardly established, and we rely on our honest and straightforward way of dealing, for securing new customers for English manufacture.

GLASS AND SILICATES.

BY PROFESSOR FREDK. S. BARFF, M.A.

The very brilliant and useful substance, which forms the subject of this article, is said to have been discovered by the Phoenicians. The story goes that some Phoenician merchants, while cooking their food on the sands near the seashore, noticed that the ashes of the plant, with which they made their fire, caused some of the sand to melt and form a vitreous substance; but whether this tale be true or not, it is well known that for a long time these people made glass from the materials which were abundant on their sea and river coasts.

Glass, however, was produced long before this by the Egyptians for the beads and ornaments used in adorning their mummies, and many specimens of these are in the British Museum. It is certain also that they well knew how to make certain substances impart colour to glass for the manufacture of most of these beads. The Romans made rich goblets of ruby glass, some of which are to be seen in collections in this country, as well as urns to receive the ashes of their dead, four of which, of a green colour, are also in the British Museum. The manufacture of these vessels proves that this nation was well skilled in the arts of blowing and modelling glass; and their designs, which we are now reproducing, show that they were at least not inferior in artistic skill to those who have formed their taste in this highly civilized age. We have no record of glass being used for glazing purposes in ancient times. The Venerable Bede introduced it into this country about 674 A.D., and employed it in the adornment of church windows. Ordinary window glass was made at the works in Crutched Friars in 1557, and plate glass at the large works of the Ravenhead Plate Glass Company, near St. Helen's in Lancashire. About 1776, flint glass vessels were blown at the establishment in the Savoy House; and the second Duke of Buckingham brought over Venetian artists, at that time the most skilled, to make glass for mirrors, carriage windows, and other useful purposes. Their workshop was in Lambeth, and the date of their arrival in this country was 1673. The French were before us in the art of casting glass plates; and in 1688, Stewart commenced this branch of manufacture, which led to the establishment of the very famous works of St. Gobain. England has now large plate glass factories in different parts of the country, and these together yield as their weekly production at least 140,000 superficial feet of the best polished plate, or seven and a quarter millions of feet yearly. The value of plate glass made in England annually, including the rough kinds used for glazing roofs, &c., is estimated at 1,000,000_l._ France still stands very high, and her plates are extremely perfect in manufacture. St. Marie d'Oignies, in Belgium, also sends a considerable quantity of plate glass into the market. This branch of manufacture has not yet extended to America, which therefore is a large customer of Europe. Formerly, glass making was very heavily taxed in this country, and in 1812 an additional duty was placed on the manufacture of the raw material, which so greatly depressed it, that the income which the State received fell from 328,000_l._ to 183,000_l._ per annum. Moreover, large quantities of foreign glass were imported, and this too hindered the development of the industry amongst us. On the repeal of the duty, however, the trade began to increase, and has now reached very large dimensions.

Glass appears to be a mixture of silicates, the nature and chemical composition of which will be explained in a later part of this article.

The materials used are principally sand, with an alkaline substance, either a salt of soda or potash and lime, though in some kinds of glass, oxide of lead takes the place of lime. Other materials are generally employed to correct impurities which may occur in the sand, and which, if present, always impart an objectionable colour to the glass.

There are two kinds of glass in ordinary use: common window glass, which may be divided into sheet, crown, and plate; and flint glass, which is used for decanters, wine-glasses, and tumblers; and, in some special forms, for ornamental stones in imitation of jewels, and also for lenses of telescopes and microscopes. The materials for making these different kinds vary somewhat, although the principal constituents are the same, viz. sand with some salt of soda or potash.

The scientific name for sand, or more properly for its principal constituent, is silica. This compound silica, or oxide of silicon, also called silicic acid, possesses properties similar to those which belong to other acids, namely, it is able, when brought into contact with bodies of an opposite character under suitable conditions, to unite with them and to form salts. Everybody knows, that if tartaric acid be added to carbonate of soda, an effervescence takes place; carbonic acid passes off in the gaseous state, and the residue is composed of a portion of the tartaric acid, which unites with the soda, a double decomposition taking place. If silicic acid be mixed with carbonate of soda, and if the mixture be heated to a high temperature, that is, to a white heat, for some length of time, the same kind of action occurs: carbonic acid goes off, the silica or silicic acid uniting with the soda; and inasmuch as the soda salt was originally called _carbonate_ of soda, after this action, in which carbonic acid is replaced by silicic acid, it is called _silicate_ of soda. Silicic acid at the ordinary temperature of the air and in the dry state, has no action whatever upon carbonate of soda, but when heated sufficiently, the action becomes vigorous. A very interesting experiment may be performed in illustration of this fact in the following manner: if a mixture of carbonate of soda and carbonate of potash be heated in an ordinary fire-clay crucible, and if, when the mixture is melted, some perfectly dry sand be poured into it, effervescence will take place, owing to the expulsion of carbonic acid from the carbonate of soda and potash by means of the silicic acid. If the operation be performed in such a vessel that the carbonic acid can be collected, its presence is readily indicated by the usual tests. This experiment can be easily made by anyone who has ordinary chemical apparatus at his command. If the mixture of carbonate of potash and carbonate of soda be melted in a small platinum crucible; and if, when melted, it be removed quickly while very hot into a tall beaker-glass, and sand be then poured into it, the escaping carbonic acid will, on account of its being heavier than air, be retained in the glass, and its presence can be recognized by its turning lime-water milky (which is, in fact, a solution of lime in water), owing to the formation of carbonate of lime produced by the carbonic acid evolved uniting with the lime dissolved in the water. A mixture of carbonate of soda and carbonate of potash is here used, because either of these salts requires a very high temperature to melt it; but when the two are heated together, the fusibility of both is increased. When sand is heated with oxide of lead (common litharge) they unite, forming a compound similar to that produced by the silica uniting with the soda, as described in the last paragraph. In the first case, a _soda_ glass is formed; in the second, a _lead_ glass is the result. If these two glasses be mixed together and melted in a crucible, and if the proportions in which they are mixed be properly adjusted, and the materials used be pure, a colourless and transparent glass will be formed, similar in appearance to that which is employed in the manufacture of decanters and tumblers. The same kind of glass may be produced by mixing all the materials in due proportions and heating them together. If, instead of oxide of lead, lime be mixed with carbonate of soda and sand, and the mixture be heated to a high temperature, a glass will be formed, in many respects similar to that of which oxide of lead is a constituent, but differing from it in several important particulars. First of all, the lead glass is highly lustrous, and has a great power of refracting light, so that, when it is cut, it presents a brilliant appearance, and by refraction readily produces the prismatic colours. This property does not belong to the glass containing lime, to anything like the same extent. Lead glass, too, is much heavier than lime glass, and is therefore unsuited to many of the purposes for which the latter is generally used, the principal of which is for the glazing of windows.

If, instead of oxide of lead, which is a chemical compound of lead and oxygen gas, or lime, which likewise is one of the metal calcium with oxygen, _carbonate_ of lead or of lime be used, the silicic acid will expel the carbonic acid from these substances at a high temperature, just as it does the carbonic acid from the carbonate of soda and carbonate of potash. It is necessary, for a proper understanding of the scientific part of our subject, that this fact should be borne in mind, and that the acid properties of silica should be thoroughly recognized. Formerly, carbonate of soda was used in the manufacture of ordinary window glass, but now it is found more economical to employ _sulphate_ of soda, which is a much earlier product in the manufacture of soda from common salt than the carbonate, and is therefore less expensive. Carbonic acid is what chemists call a _weak_ acid, by which is meant, that its compounds are not so firm and stable, as those which are formed by other acids with the same substances. Sulphuric acid is a strong and powerful acid, uniting very readily with the oxides of certain metals to form very stable compounds. But although this acid is chemically so powerful in its compounds, yet at a high temperature it is expelled by silicic acid, showing that this substance, so inert in its natural state and at the ordinary temperature of the air, becomes exceedingly active in expelling other acids and in forming compounds, when put under favourable conditions.

If a mixture of common sand and carbonate of soda, the carbonate of soda being in excess, be heated, a glass will be obtained which is slowly soluble in cold, readily soluble in hot water. To these compounds the name of silicate is given, so that we speak of the soda compound as silicate of soda, of the lead compound as silicate of lead, and the lime compound as silicate of lime. Silicate of soda and silicate of potash, when the alkali, that is to say, the soda or potash, is in excess, are both soluble. If a solution of one of these silicates be taken, and if carbonic acid be passed slowly through it, after a time a gelatinous, white, flocculent substance will be formed in the liquid, and eventually precipitated. This white flocculent substance is silicic acid combined with the elements of water, and is therefore called by chemists hydrate of silica. Now this hydrate of silica is soluble in water and in hydrochloric acid; and the method by which it can be brought into solution in water will be explained, when treating fully of what are called soluble silicates and their applications.

Soluble silicates are mentioned here, in order that a more perfect understanding of the nature of silicious compounds may be obtained, by those who do not possess a scientific knowledge of chemistry. The silicic acid in the silicate of soda is precipitated or separated out by carbonic acid, and hence it appears, that an action, exactly the reverse of that which takes place at a high temperature, occurs, when the silicic acid is removed from those conditions in which it has been seen to be (chemically) so active.

Suppose that to a solution of silicate of soda or of potash a soluble salt of calcium be added--the chloride, for example, which is a compound of the metal calcium with chlorine--a double decomposition will take place; the calcium will unite with oxygen in the silicate of soda, forming lime; and this will again unite with the silicic acid, forming silicate of lime; while the chlorine will unite with the sodium, forming chloride of sodium, or common salt.

Here then, silicate of lime is obtained by a process very different from that which has already been described, namely, by the heating of lime with silica at a high temperature. The body formed in the latter case is chemically the same as that produced in the former, there being present the same weight of calcium, the same weight of oxygen, and the same weight of silicic acid in each. Again, if to a solution of silicate of soda, one containing a soluble lead salt, such as the nitrate, be added, the silicic acid will unite with the oxide of lead in the nitrate of lead, and the acid constituent of that body will unite with the oxide of sodium or soda, forming nitrate of soda. It is apparent, therefore, from these remarks, that in whatever way the substances be made to unite, the effects produced as regards chemical composition are the same. If some of the silicate of lime or silicate of lead made by precipitation be dried and heated to a high temperature in a crucible, it will melt or fuse, and form a vitreous substance. In these last cases, as in many others which will have to be alluded to, the silicates formed are not soluble in water, although silicate of lime may be partially dissolved when heated in water under extreme pressure, by which the temperature is considerably increased, and even slightly in cold water.

To ensure the production of definite silicates by the agency of heat, the materials must be mixed together in proper combining proportions; for if more of the metallic oxide is introduced than can combine chemically with the sand, it will be melted in the mass, but the excess will not form a definite compound; whereas by precipitation, the silicates formed always have, when thoroughly washed, a definite composition. This subject will be again referred to, when the manufacture of commercial glass is described.