Enameled brick have been unearthed in China which are supposed to be four thousand years old. I have seen specimens of these brick, and the glazed surface is as perfect today as it was when made. They are really glazed porcelain brick, and the term enameled, as applied to them, is a misnomer. The body of the brick is thoroughly vitrified, and of a fair color. From the superior color of the face, these brick were evidently coated with a slip of better quality than the body, and then glazed. No evidence of a slip can be detected, however, as the gradation from glaze to body is so gradual that it is impossible to tell where one begins and the other ends. Were they burned in one fire or in two? History does not tell us, and the brick themselves are silent on the subject. From their nature, they were evidently not burned open, or, if so, were not set more than two or three high. The probabilities are that they were burned in saggers, as the vitrification is so complete that they probably would stand very little beyond their own weight How many of the enameled brick of today, of which we are so proud, will live through four thousand years? Have these brick existed through four thousand years? We cannot say positively, but whether they have or not, they are capable of it, and, furthermore, they will last forever. They are practically indestructible, and when we of to-day make as good glazed brick we will have just reason to be proud of them.
The Assyrians and other nations have produced enameled brick, usually made of a rather soft, lightly baked body, and coated with an extremely soft enamel. How they have managed to hold together so long is a mystery.
The English have been making enameled brick and glazed sanitary ware for years; just how long I do not know. Their product has been of better quality than anything made in this country up to a very few years ago.
Enameled brick have been made in Philadelphia for the past fifteen to twenty years, and in Zanesville, O., for a number of years. The process employed is the double fire, regular enameling process. In most of these factories the body was and is of a red clay.
I believe the first plant for the manufacture of glazed brick by the single-fire process was established at Oaks, Pa. This plant was built in 1888. It was soon followed by the Sayre & Fisher Company, of Sayreville, N. J., and they, in turn, by the Tiffany Pressed Brick Company. There has been in existence for some years, at Somerset, Mass., a plant that, when known to the writer, used the double-fire process on a fire-clay body. The American Enameled Brick Company has lately commenced operations. Process and methods are unknown to me. Besides these concerns, there are several places where a few enameled brick are made. The glazed sanitary business has not, I believe, reached very large proportions as yet, though there are several concerns making this class of goods. Glazed terra cotta is also being made to a limited extent.
The demand for these goods is certainly on the increase, and will be for years to come. The consumption of enameled brick alone in Great Britain has been very large, and it will be so in this country when the supply is assured at reasonable prices. The importation of enameled brick has been attended with considerable annoyance, and the manufacture of a good article at home meets with much encouragement
Statistics on importation are impossible to obtain, as goods of this character are not specially classified, or have not been until lately. The importation of enameled brick must amount to three or four million per year, and the importation of glazed sanitary ware is large.
From the Statistics of the Clayworking Industries of the United States for 1894 we obtain the information that in 1893 about four and one-half million enameled brick were made, and that these were sold at an average price of $90 per 1,000. I see no mention, in that work, of glazed sanitary ware, so take it for granted no one was making it in 1893.
Our clays have not been thoroughly investigated with a view to their suitableness for this class of work, but I have no hesitation in saying there are thousands of them, of which 70 or 80 per cent could be used in the composition of bodies suited to it, and there are hundreds of localities where the whole of the components of a suitable body can be found within a very small space. Often two clays, either one of which alone would be eminently unsuitable, in nearly every way, when properly combined make a fine body, and there are many clays which are nearly right and a slight admixture of another clay, of proper qualities, renders perfect
It may require a glazing expert to determine when these conditions exist, but the following pages may enable the reader to determine it in a number of cases.
There is a wide field as to methods and schemes that may be employed, and much time and money is often wasted trying to use a method that is ill adapted to the clay. Just how far it pays to try to glaze a clay that is not adapted to the simpler and cheaper methods is for each individual to determine for himself. But it is easily determined that it never pays to turn out a finished product of inferior quality. So let the method be one that, with the clay in use, will produce a fine article, or change the clay, even at considerable expense, to suit the method. In regard to kilns I have said little, for there is such diverse opinion on this subject, and people's ideas are generally so firmly fixed that the less said the better. I may be criticised for giving so few receipts, but I consider them so almost utterly useless, except as suggestions, that I do not consider them worth the room they take up. The receipts that are given are practical receipts, and upon the proper clay and at the proper heat will give fine results.
The quality of some of the enameled brick now being made in this country seems to be excellent The Statistics of the Clayworking Industries of the United States in 1894 makes the following statement in regard to some tests of enameled brick made in this country: "The specimens were cubes averaging about 1.88 inches on each edge, with the enamel on one face, and were tested on the Emory Hydraulic Testing Machine, at Columbia College, New York. The pressure was applied parallel to the face having the enamel on it. The specimens were crushed at an average pressure of 4,260 pounds per square inch, and in no case did the enamel crack or scale before the specimen failed."