INTRODUCTION.
The decoration of pottery under the glaze offers opportunity for the production of work, beautiful and artistic in a high degree, and in its simpler forms gives to those who do not aspire to the higher art, a most fascinating and labor-rewarding study. I can not, however, assure those who wish to enter the domain of decorative art by this interesting road, that they will find the way strewn with roses. On the contrary, discouragements are likely to occur so frequently that it is only by the exercise of a considerable amount of patience and perseverance that any advance can be made. But such are the attractions of the work that its enthusiastic votaries will not be deterred from its prosecution by any difficulties in the way, and if immediate and perfect success can not be assured, an exceedingly interesting occupation will be revealed to the learner, and to the earnest worker can be promised the reward of faithful labor.
I would like here to insist, however, upon the necessity of a thorough and serious study of drawing as a preparation for this as well as for all decorative work, and to enter a most emphatic protest against the theory which seems to prevail in some quarters, that any one can paint upon pottery acceptably. With little preparation other than the possession of some colors, brushes, clays, and pieces of pottery, the devotee of art enters upon the work of decorating (?) pottery. Alas! disfiguring it, for it is a lamentable fact that of the pottery now being painted by amateurs (some of the work by professional decorators might also be included) a very large proportion has its value diminished rather than enhanced by the work put upon it.
This would not be so frequently the case if the scope of the work were limited to the capacity of the worker. We see every day, attempts, in which the failure to reach the point aimed at is absurdly obvious, where, if the effort had been less ambitious in its aim, the result would not only be less an object of ridicule, but of far more intrinsic value.
In other departments of human handiwork, some natural capacity, as well as a certain amount of training, is considered necessary to successful practice, but, in art, such is the ignorance of the general public, any one is thought eligible to the profession of an artist, and much passes under the name of art, which has no claim to that honorable title.
I do not wish to discourage those who are willing to enter into this pursuit as humble, patient learners, but to warn those, who are eager to obtain at once the rewards only given to years of faithful study, of the futility of their desires. It is perhaps idle, however, to warn or to advise them. The consciousness of their folly will only come to them after experience, and knowledge gained from failure, shall have given them some comprehension of the difficulties which their ignorance prevented them from seeing.
In art, as in all other pursuits, there is no royal road to excellence, and those who do not think it necessary to learn the rudiments before attempting the higher branches, will learn to their cost, if they are capable of learning any thing, that nothing was gained by leaving out these stepping stones in their progress.
The time is never misspent which is devoted to honest, well-directed efforts in acquiring the art of drawing. The excuse so often offered, that the practice of the art is only intended as an amusement, and that therefore it is unnecessary to undergo the drudgery of learning it thoroughly, is one which is unworthy. To those who offer it I would say, pray amuse yourselves with something else rather than an art, into which, to obtain even an insight, demands the best that any one can give.
These remarks apply as well to the decoration of pottery as to any other department of art work. Although from its peculiar nature and various uses this material yields itself to many and varied styles of decoration, yet this decoration, however simple, must be planned and executed according to sound principles, to be of any artistic value. The best preparation for the work of decorating pottery, therefore, is a thorough knowledge of drawing and an understanding of the laws which govern all decorative art.
Sources of information upon these subjects, drawn from competent instruction, books and periodicals, are daily becoming more numerous and accessible, and one who desires to practice the kind of decorative art we are now considering, should cultivate his taste and augment his skill by these means, and especially by close study of nature in all its various forms. It is only in this way that the student will be enabled to accomplish work which will be a source of pleasure and profit to himself and others.
POTTERY DECORATION UNDER THE GLAZE.
CHAPTER I.
POTTERY.
We will consider in this chapter some facts in regard to pottery, which, although of a very elementary character, are not so generally understood as may be desirable. These facts relate to the substances of which pottery is composed, the processes of its manufacture, and the methods by which it is or can be decorated.
Two chemical substances, viz., silica and alumina form the basis of all pottery clays. These substances are themselves infusible (except under the compound blow-pipe), but by admixture with other materials more susceptible to the action of heat, they are made useful to the potter’s art, and, when subjected to a high temperature, fuse and form the hard, insoluable combination with which we are all familiar.
Porcelain, and the finer kinds of earthen-ware, are made from clays artificially combined of various natural elements, in such a manner as to produce the qualities desired, while the coarser wares are generally made from clays in a natural or unmixed state. These clays agree in their essential characteristics, but contain other elements which cause certain differences of color, susceptibility to heat, plasticity, etc. The differences, therefore, which exist between the many kinds of pottery manufactured, may be said to be due, not so much to a diversity of the materials used, as to the changes produced by the combination of the same materials in varying proportions.
It is unnecessary that we should here enter into the details of the mixture of different pottery clays, for which each manufactory has its own formula. A few words, indicating, in a general way, the causes of certain easily-recognizable qualities, will suffice.
The peculiar beauty and translucency of fine porcelain, is due to an excess of silica, or the vitreous element of pottery, in its composition. This is attained by the use of kaolin, a fine, white clay, produced through the agency of natural causes in the decomposition of feldspar, which is itself a silicate of alumina, and one of the principal ingredients of granitic rocks. In porcelain, it may be said, that the proportion of silica to alumina is about three to one, and the other ingredients, such as iron, potash, chalk, and soda, exist only in such quantities as are necessary to cause the fusion of the two first-mentioned elements. It is fired but slightly the first time. This leaves the body of the ware very soft and porous, and upon the application of the glaze the latter is absorbed into the body, and by its action upon the materials composing it, produces a translucent effect.
We refer, here, to French porcelain. In the manufacture of English china, the process is radically different. The last-mentioned ware is sometime spoken of as “bone china.” This term has reference to the use of bones from which the lime required in its manufacture is obtained. This element produces a translucent quality in the body of the ware independently of the action of the glaze, which in this case forms merely a coating upon the surface of the previously hard baked body.
Earthenware possesses less of the vitreous element, and the first firing is continued until the ware becomes so dense that it will not absorb the glaze, and the body remains opaque.
The term pottery, is more strictly applicable to the kind of ware last mentioned. It is to this that especial reference will be made in the following pages, in describing methods of manufacture and decoration.
Earthenware is of various colors, ranging from pure white, through the cream white and cream-colored wares to decided yellow, and lastly red. The clays can also be artificially colored, and changes in color are also produced by different degrees of temperature in firing. Ordinarily the process of firing produces a material change in the color of clay. Thus, a grey-tinted clay will assume a bright, yellow color, and a dull brown, green, or blue will be changed to a bright brick-red, under the action of the fire.
The heat used in firing should produce partial vitrification. If a piece of ware has not been fired sufficiently to produce that effect, it is said to be “soft-baked.”
White earthenware requires the greatest degree of heat in firing. In regard to the wares made from clays retaining the colors produced by the elements which they contain, in a natural state, it may be said that the amount of heat necessary for proper firing, decreases with the depth of color. This rule, although it may accurately indicate the temperature at which any given clay should be fired, is simply artificial, except in so far as the depth of color shows the presence of an amount of foreign matter, which by its action increases the fusibility of the clay.
Red clay, being very susceptible to heat, is commonly used as a test in the firing of white ware. The same clay will change in the process from light red to dark brown, and so enable the experienced fireman to determine the degree of heat existing in the kiln.
Clays should be prepared for the making of pottery by careful sifting, dissolving in water, and, as a final precaution, straining through sieves made of fine, silk lawn. In this way all foreign particles are removed, and the clay, having attained the consistency of dough, is ready to be molded into the shapes desired. This is done in molds made of plaster of paris, or it is “thrown” by the hands of the potter on a turning-wheel, or, again, by a combination of these processes.
Before firing, the ware is said to be in the “green state,” in which condition it passes from “wet” to “hard green,” and finally to “white,” when it is ready to be fired. If fired before it has become sufficiently dry, it will be liable to crack, or scale, from the sudden expansion of the moisture confined in the clay. When dry, it is placed in “seggars,” or boxes, made of fire-clay, which are piled upon each other in a kiln, constructed for the purpose of firing the ware.
During the process of drying and firing, the clay loses a certain portion of its bulk. The amount of this shrinkage varies in different clays, but ordinarily may be said to be about one-eighth. A piece of ware, therefore, made from clay which exhibits this degree of shrinkage, would be one-eighth smaller after firing than before. The shrinkage is also modified by the degree of heat to which the clay has been subjected in firing, and there will sometimes be a perceptible difference in the size of two pieces of ware, made from the same clay, and of equal size before firing, after having been fired at different temperatures.
The length of time consumed in firing, varies with the qualities of the different wares. In the manufacture of white earthenware, the firing lasts from thirty to forty hours, while the more common kinds of ware require less time. In kilns of ordinary size, a thousand dozen pieces of ware are frequently fired at once. Of course, considerable time is required to place the seggars containing the ware in the kiln. Some hours must elapse before the kiln and its contents will become cool enough to permit its being opened with safety, so that the firing of hard-baked pottery may require two or three days for its completion.
The first firing completed, the ware is said to be in the “biscuit,” and is then ready to be glazed. This matter of glazing is a very important one, and the success of the whole very largely depends upon the manner in which the operation is performed. To insure a successful result there must be the nicest adaptation of the materials composing the glaze to the body of the ware. The glaze for each kind of ware must be suited to its especial characteristics, and it can therefore be imagined that the number of glazes in use is very large. Each pottery has its own glaze and the variety is infinite.
The glaze used upon the finer kinds of earthenware consists of materials similar to those of which the body of the ware is made, with the addition of boracic acid (a powerful flux), which with a little lead renders the glaze fusible. In the lower grades of ware a larger amount of lead is used for a flux, and this causes the glaze to fuse at the comparatively low temperature at which these wares are fired. A glaze made of materials that fuse at an unusually low temperature is called a “soft” glaze. Some glazes are so soft that, when fired, they can be easily scratched by the point of a steel instrument. The glaze of good and durable wares is, however, so hard, that the point of the sharpest knife will make no impression on its surface.
The materials of which the glaze is made, are combined in the proper proportions and diluted to form a liquid of about the consistency and the appearance of cream. The piece of ware is then dipped carefully into the liquid, and so skillfully manipulated that it is completely covered with a coating of the glaze of the necessary thickness.
After having been covered with the glaze, which, before firing, has the appearance of an opaque white paint, the ware is ready for the second firing. This is done in what is called the “gloss” kiln, in which the heat is not brought to such a high degree as in the biscuit kiln, but is sufficient to fuse the glaze, and cause it to form a glassy, transparent surface, which should completely cover the body of the ware, and present an equally brilliant appearance in every part.
If the glaze is not suited to the body of the ware, and does not shrink equally with it, its surface will soon present a network of fine cracks. A glaze in this condition is said to be “crazed.” This, among potters, is considered a serious fault, and in ware intended for cooking or table use, is certainly very undesirable.
Old Japanese crackle-ware, in which this condition is a distinguishing feature, is, however, much esteemed, and many, indeed, the majority of the Japanese earthernwares, both ancient and modern, display a surface of fine-crackled glaze, which may not be said to detract from their value as articles of ornament.
A similar effect is also seen in old pieces of glazed ware which have seen long service as cooking utensils, in which case it has been the natural result of the usage to which they have been subjected.
In some modern wares, both French and English, decorated under the glaze, this defect is seen. In these cases it has been caused by the use of a softer glaze than the body of the ware demanded. This expedient has been resorted to in order that the brilliancy and beauty of the colors might be preserved. These articles being intended only for ornament, beauty is more of an object than durability, and this defect of glaze may be permissible as the means of obtaining more brilliant effects. In certain methods of decoration this may be a necessity, but these cases are exceptional and experience leads me to believe that it is possible to obtain beauty of coloring with a glaze which will remain intact. It is to be hoped, however, that with the improvements in making colors the time may come when it will be possible to obtain colors which will retain their beauty under the degree of heat necessary to the production of an article which a practical potter would call a perfect piece of ware.
Pottery can be decorated either under the glaze, with the glaze, as in the case of majolica, in which the color is effected by the use of colored glazes and in the decoration of soft porcelain (pâte-tendre), where the painting is executed upon the unbaked glaze, and, lastly, over the glaze. We will concern ourselves only with the first of these methods. A few words, however, may not be out of place here, upon the differences between over and under glaze painting, which are frequently compared and as frequently mistaken for each other.
Over-glaze painting, as is well known, is executed upon the glazed surface of the finished ware with vitrifiable colors having enough flux or fusible material in their composition to cause them to fuse at a comparatively low temperature, and so become attached to the glaze. Under-glaze decoration is effected by the use of colors which contain less flux, and consequently require a higher temperature for their fusion. It can be executed either upon the ware in the “green” state, or, as is more commonly the case, in the biscuit. These two methods of painting differ materially in their effects. Any one familiar with these effects can readily discover whether a piece of pottery has been decorated over or under the glaze. Those who are not practically conversant with the two methods can be easily misled, and mistakes are frequently made by those who should know better, as to the method employed in the case of a piece of ware in question.
A certain delicacy of tint and firmness of outline characterizes overglaze painting, which is easily recognized by experts, but those who can not distinguish between the two methods by this means may ascertain to which class the decoration belongs by looking aslant the surface. The glaze upon the painted portions of a piece of ware decorated over the glaze, will not, even after the most perfect firing, equal the glaze upon the uncovered portions in brilliancy, and there will probably be certain inequalities of surface between the painted and unpainted parts which will be revealed to the touch.
If the decoration has been executed under the glaze the surface will be uniformly covered with a brilliant glaze. Of the two, underglaze painting is probably the most difficult, as the colors are more liable to change under the action of the great heat to which the ware must be subjected, and the final results being, therefore, somewhat uncertain, can not be accurately counted upon, until experience has been gained from repeated failures. On the other hand, overglaze painting, while not subject to the changes produced by the fire, to so great an extent, is more difficult as regards the manipulation of the painting upon the glazed surface. The facilities for the practice of overglaze painting are greater than those afforded for painting under the glaze, which last, requires not only the handling of an artist who has acquired facile use of the brush and some experience of pottery clays and colors, but also the assistance of an intelligent and skillful potter.
Let us not, however, laud one method of painting at the expense of the other. Both are good in their way, and confined within their proper limits, have beauties peculiarly their own. Overglaze painting possesses a delicacy of effect and a variety of color which the underglaze decoration can not rival. The latter is, however, the most artistic as well as the most effective, and lends itself more readily to the uses of decorative art and to the modern taste in color.
It is this latter method of decorating pottery which we will now consider in some of its various forms.
CHAPTER II.
COLORS FOR PAINTING UNDER THE GLAZE.
Colors for painting under the glaze are specially prepared for the purpose from various metallic oxyds. As mentioned in the previous chapter, the colors used under the glaze have less flux or fusible matter in their composition than those used for painting overglaze: this is necessary, because in the former the colors are expected to bear a much greater degree of heat in firing than in the latter. They are so prepared as not to fuse except at the temperature required in the manufacture of the pottery to which they are applied. The variety of underglaze colors is less than that to be found in overglaze colors, as the oxyds from which colors may be made which will stand so great a degree of heat, are few in number.
The oxyds from which the colors are prepared are called the bases of these colors. The colors used in underglaze painting are made from the following bases:
Blue from the oxyd of cobalt. Co. O.
Green from the sesquioxyd of chromium. Cr2. O3.
Browns from the sesquioxyd commonly called the peroxyd of iron, Fe2. O3., and from the sesquioxyd of manganese. Mn2. O3.
Yellow from the compound of titanium with oxygen, called titanic acid. Ti. O2.
Black from the oxyd of uranium.
Red from the suboxyd, or red oxyd of copper. Cu2. O.
We may add, upon the authority of M. Debette, that “pure black is obtained by taking 1 part of oxyd of uranium diluted in 22 parts of glaze; ordinary black with oxyd of manganese or oxyd of iridium; bluish black with a mixture of oxyd of cobalt and of manganese, and smoky grey with chloride of platinum. Rose is obtained by diluting, in glaze, gold which has been dissolved in aqua regia. For the blues, oxyd of zinc and alumina may be mixed with the oxyd of cobalt. For greens may be mixed oxyd of cobalt and oxyd of chromium.”
The fluxes used for these bases are given in the following paragraphs, translated from the Encyclopédie-Roret:
“The matters which enter into the composition of the fluxes and which cause the adherence of the metallic oxyds are quartz, feldspar, borax and boracic acid, nitre, the carbonates of potash and of soda, red lead and litharge, and oxyd of bismuth. At Sevres, they employ, for under-glaze painting, seven kinds of fluxes, which suffice for all the colors. The majority of these fluxes are composed of quartz, oxyd of red lead and of boracic acid, and to some is added a small quantity of carbonate of soda.
“The seven fluxes of Sevres are, first, the flint flux, which is prepared by melting quickly in a crucible and then flowing upon a metallic plate a mixture of 3 parts of red lead or of litharge, and 1 part of Etampes sand.
“Second. The flux of greys prepared with 6 parts of red lead or litharge, 2 parts of Etampes sand, and 1 part of pulverized borax.
“Third. The flux of carmines is made of 1 part red lead, 3 parts of Etampes sand, and 5 parts of pulverized borax.
“Fourth. The flux of purple is made with 3 parts of red lead or of litharge, 1 part of Etampes sand, and 5 parts of crystallized boracic acid.
“Fifth. The flux of violets is made of 27 parts of litharge or red lead, 2 parts of Etampes sand, and 11 parts of crystallized boracic acid.
“Sixth. The flux of greens employed, as well as the two preceding M. Salvetat, was prepared by him with 8 1-9 parts of red lead or litharge, 1 part of Etampes sand, and 2 parts of crystallized boracic acid.
“Seventh. Last the flux of the metallic substances, which is of sub-nitrate of bismuth, obtained by decomposing in water the nitrate of the acid of bismuth, to which is added 1-12 of borax.”
These fluxes are mixed with the basic oxyds in greater or less proportion, according as the colors are intended for work, which will require a greater or less degree of heat in firing.
Underglaze colors in powder suitable for painting on pottery, can be procured of several different manufactures. As mentioned before, the variety of these colors is not so great as is to be found in overglaze colors, but as they can be readily mixed the number is sufficient for all practical purposes.
In my own work I have made almost exclusive use of French colors, those manufactured by M. Lacroix. These colors are finely ground and of considerable variety of tint. A list of those which have been tried and found to give satisfactory results, may be given here:
Blues—Bleu de Roi (King’s blue).
Bleu violacé (violet blue).
Light blue—Bleu myosotis (Forget-me-not blue).
Reds—Rouge T. (Red T.) and Rouge P. W.
Carmine—Rose (or Pink).
Greens—Vert foncé, No. 1 (dark green).
Vert tendre (light green).
Black—Noir.
Browns—Brun foncé (dark brown).
Brun No. 5 (Brown No. 5).
Brun jaune (yellow brown).
Yellow—Jaune foncé (dark yellow).
Grey—Gris clair (light grey).
There are many others, but these are mentioned as among those that have been tried and found to fire well, and the colors given in this list will be sufficient for the production of all the tints needed in underglaze painting. In faience painted after the Haviland method, fine white clay takes the place of white.
In painting on the biscuit white paint is sometimes used. This can be procured of English manufacture, but is not, I believe, made by M. Lacroix. The colors manufactured by Messrs. Hancock & Sons, Worcester, England, are also very satisfactory. The tints of these and the colors of other English manufacturers corresponds with those of M. Lacroix, which have been mentioned. The latter manufacturer, however, furnishes a much greater variety of colors, and the reds especially are superior to any English reds I have seen. M. Lacroix’s list includes at least three reds, one of which, Rouge T., can be relied upon to produce as good a scarlet as is possible under the glaze, when used under the proper conditions. The English carmines are very satisfactory. The English green, called French green, corresponds in tint to that of M. Lacroix, called Vert foncé, No. 1, while mazarine blue, of the Worcester and Phillips manufactures, and Cobalt blue of others corresponds to the Bleu de Roi of the French, and for work on biscuit white ware stands the fire rather better. The Victoria green, of the Worcester colors, is especially to be commended for a light green which stands the fire remarkably well.
Phillips’ English colors are also very good. His mazarine blue, especially, is one of the finest blues I have ever met with. Emery’s and Harrison’s colors fire very well, but are not so finely ground as the first mentioned.
CHAPTER III.
PAINTING ON POTTERY AFTER THE MANNER OF
THE HAVILAND OR LIMOGES FAIENCE.
This method of painting on pottery is said to have been discovered by M. Laurin, at Bourg-la-reine, in the year 1873. The process was afterward adopted by M. Haviland, and by him improved in such manner as to materially change the method, as well as the appearance of the painting. Specimens of the ware were first exhibited at the Centennial Exhibition, in Philadelphia, in 1876. The first application of a similar style in the decoration of pottery, in this country, was made by the writer in Cincinnati, in October, 1877.
This method of decorating pottery, although not involving the use of any new principle, was yet so entirely novel an application of principles already in use, as to entitle M. Laurin to all the credit attaching to a very original and important discovery. It places in the hands of the painter of pottery a method at once so artistic, and so thoroughly in accord with the modern school, as to awaken a profound interest in the minds of all lovers of art. It is probable that there are capabilities in this art that have not yet been brought out. It is still in its infancy, and that there are in it possibilities of much importance to the artistic world, can hardly be doubted.
If it were not for the technical difficulties which surround all work on pottery, and this style in particular, it would offer facilities for the production of works of art unequaled by any method heretofore in use. It is the hope of the writer that the following description of the method of decorating pottery, in this manner, may throw some light upon these technical difficulties, and also that artists of ability may be induced to try it, and so demonstrate the capability it undoubtedly possesses.
The mere knowledge of the materials used will, however, no more produce artistic work, than a box of Winsor & Newton’s colors, in the hands of a beginner, will enable him to paint a picture, equal to one by Titian. To produce good work in this method, there must be a certain amount of skill at the command of the painter, just as the same degree of skill is requisite in the production of a good picture by any other method. There is a certain boldness of effect produced by the very nature of the materials and process, which probably would not be seen in the work of the same person in other methods, yet the lack of artistic feeling and ability will be as painfully apparent in this as in any other.
Colors may be daubed upon pottery, as they are, alas! upon canvas, by those whose training and whose feeling for art would hardly fit them to become good house painters; but the result will not be good art, nor will it ever be its own excuse for being. If other branches of decorative art require taste, knowledge, and practical skill, so much the more does this, when it offers scope for the highest capacity. To the artist of ability sufficient to make use of it, it furnishes a palette which, although not of the same range as that of oil colors, yet affords an almost unlimited scale of colors, each of which is enhanced to the fullest degree by the brilliant glaze, with which the work is finished. The painting executed with these beautiful colors, moreover, is practically unchangeable, and none of the ravages of time, short of the destruction of the piece of ware itself, can affect it. In decorations for buildings, or for ordinary use in portraiture, or the higher forms of art, it offers, what has long been desired among artists and art lovers, a method of making works of art indestructible and beyond the possibility of change.
The ware known among dealers under the name of “barbotine,” has some resemblance to that which we have been considering. It has a light body, which has been subjected to a very slight fire, and is covered with a soft glaze, which ensures great brilliancy of coloring. The ware, however, has no durability, and is a substance that would not stand the action of the elements, if used in external decoration.
CHAPTER IV.
METHOD OF PAINTING FAIENCE UNDER THE GLAZE
WITH THE USE OF BODY COLOR.
The method of decorating pottery here described is similar in its effects to what is known as the Haviland, or Limoges faience, and is given as the result of numerous experiments made by the writer.
The finished work presents the appearance of a painting in oil, to which a brilliant glaze has been applied. This glaze not only renders the colors unchangeable, but gives a beauty and effectiveness which could be acquired in no other way. There is nothing peculiar in regard to this glaze, however, the only requisite being that it should be suited to the body of the ware, and that the latter and its glaze must not require so great a degree of heat in firing that the colors shall be injured. This matter of the glaze has been almost uniformly misrepresented in accounts of the ware which have been published. It has been said that the peculiar effect of the work was due to the glaze, and that the secret of making it was not generally known. This is not at all true, as the results are due solely to the peculiar method of painting, and the glaze is simply the process by which it is finished, and bears the same relation to it as the varnish does to the painting in oil. The work will suffer, of course, if this part of it is not well performed; but the distinguishing feature of the method consists not in the glaze, but in the use of clay, which is mixed with coloring oxides, capable of bearing a high degree of heat in firing, and which gives them body, producing a thick impasto in the painting. The work partakes, therefore, both of the nature of painting and modeling, as the high lights may be laid in so thickly as to produce an actual relief.
It is somewhat difficult, indeed, almost impossible, to give a correct idea of the palettes to be used in this kind of painting. If colors could be procured, already prepared for use, as oil paints are, and these colors had the same appearance after firing as before, it would be comparatively an easy task. As it is, the colors must be mixed with clays in certain proportions, and, on account of the change produced by firing, the proportions necessary to produce the intensity of color desired, can only be determined from experience. The result, after the work is finished, differs from its appearance before firing to a greater extent than in any other kind of decoration upon pottery. As a rule, it may be said that the colors are intensified by firing. This is also true of other kinds of under-glaze painting, but not in so great a degree as in the case in question. The harmonies and contrasts of color can be kept only in the mind of the artist, and every part of the work must be done with a view to the result when finished, which, as has been said, will differ materially from its appearance during the progress of the painting. Experience only, can give an accurate idea of these changes. This, however, is not an insurmountable difficulty; care and patience added to the requisite artistic ability, will soon lead to satisfactory results.
Before describing the method of painting, it may be well to consider the kind of clay of which the body of the ware should be made, and the state in which the painting should be applied. As to the clay forming the body of the ware, it must be of such a nature as to adapt itself to a glaze sufficiently soft to preserve the colors. As the clay used in the painting must, of necessity, in most cases, be white, in order that the purity and beauty of the colors may not be affected by admixture with it, a body of the same, or very nearly resembling it, would, in some respects, be the best, one reason for this being that the applied clay would be more certain to adhere firmly to the body, both having the same qualities. The proper glaze for such a body would, however, require too great a degree of heat in the firing, and none but the strongest colors could bear it without injury.
In order, therefore, that the glaze may be perfectly adapted to the body of the ware, and yet require no greater degree of heat than the colors used in the painting will bear, it is best to use a body formed from materials which do not need to be fired at a very high temperature. This desired quality is found in some of the natural colored clays. A mixture partaking of the qualities of both yellow and red clay, without the unpleasant color of the former, and possessing greater strength than the latter, has been found to be the best.