Read Ebook: How to Enamel Being a Treatise on the Practical Enameling of Jewelry with Hard Enamels by Chapin Howard M

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PREPARATION OF THE ENAMEL 1

PREPARATION OF THE METALS 8

CHARGING 14

FIRING 23

STONING 29

POLISHING 37

FOILS--PAILLONS--GLITTER ENAMEL--DULL 42 FINISH--PLIQUE-?-JOUR

ENAMEL PAINTING 50

PHOTOGRAPHS ON ENAMEL 57

FIG. PAGE

PREFACE

The aim of this book is to explain practical enameling in such a way that one entirely unacquainted with the subject will, after a little study, not only understand the fundamental principles of the art, but with a little practice be able actually to achieve creditable results in this most fascinating branch of the jeweler's craft.

INTRODUCTION

Enamel is really a glaze applied to metals just as other glazes are applied to porcelain, glass, and earthenware. We will confine our attention to what is known as hard enamel in contradistinction to japans, lacquers, and enamel paints, which are often called soft enamels. Hard enamels are compounds of glass with different metallic oxides which produce the different colors. These compounds are fused together at a very high temperature and on cooling become extremely hard. They fill the gap between glass and china, the transparent fondants being to the layman indistinguishable from glass, while the opaque whites may be easily mistaken for china, and the countless other varieties form a chain of scarcely perceptible gradations from one extreme to the other.

The use of enamels is both very ancient and very widespread, for we find the process known to the ancient Egyptians and to the Chinese, although the highest development in the art was reached in France in the sixteenth century. We would refer the historical student to Cunynghame's "European Enamels" in English and Luthmer's "Enamel" in German.

Jewelry enameling is usually divided into five different classes, viz: champlev?, cloisonn?, incrusted, plique-?-jour, and enamel painting.

Champlev? enamel is that in which a part of the metal is cut away, leaving a depression which is filled with enamel to the level of the surface of the metal, thus giving a sort of inlaid effect. If the enamel surface is not filed off flat but allowed to have a concave or convex surface the piece is said to be "flushed." Technically enamel is "flushed" if it is not "stoned." When transparent enamels are used and the background under the enamel is cut in relief, it is called "Baisse-taille enamel."

Cloisonn? enamel is hardly distinguishable from champlev? when finished, but is made differently. Instead of cutting depressions in the metal to hold the enamel, metal wires are soldered on the smooth surface of the metal, thus forming partitions or fences between which the enamel is placed.

Incrusted enamel is that in which the enamel is charged directly on the metal surface without any raised metal edges to hold it. It is generally used in small daubs or beads to reproduce the effect of precious stones.

Plique-?-jour enamel is similar to cloisonn? except that the wires are soldered to each other without any background, thus forming a sort of filigree, the spaces within which, when filled with enamel, somewhat resemble a stained-glass window.

In enamel painting a picture is painted on the enamel. Usually white opaque enamel is used for the background, and the painting is executed with finely ground enamel or china paints, after which it is covered with a layer of transparent enamel which serves as a protection for the painting.

PREPARATION OF THE ENAMELS

ENAMEL is generally bought in the form of hard chunks more or less flat and varying from the size of an acorn to that of a large dinner plate. When it is made it is poured into a mold where it hardens in the form of a disk or slab generally a foot or more in diameter, and later gets broken into smaller pieces during transportation.

These chunks of enamel may be readily broken up by a hammer, and if they are first wrapped in a piece of cloth the small particles will not fly about and get into one's eye, and no enamel will be lost. When the enamel has been broken up so that none of the pieces are larger than a pea, it should be washed in clean water to free it from any dirt that it naturally contained or that it received from the cloth in which it was wrapped during the hammering process.

Cleanliness cannot be too much emphasized, for the slightest particle of dirt mixed in with the enamel may often completely spoil a piece of work.

Enamel if heated quite hot and then plunged into cold water will become so brittle that it can be broken up by the hands, but when treated in this manner is said to be harder to grind.

After the enamel has been broken up into small pieces it should be put in an agate or porcelain mortar and ground to a fine powder. This will take from twenty to twenty-five minutes of steady grinding, the length of time depending on the quality and quantity of the enamel, the strength used, etc. Water may or may not be mixed with the enamel during the grinding process, as the grinder prefers. If water is added the process may take a little longer but a very disagreeable noise is eliminated and the work may perhaps be slightly easier. Agate mortars are cleaner and so better than porcelain ones but are so much more expensive that they cannot be used for grinding large amounts. For this grinding machines or weighted pestles, such as Cunynghame describes in his "Art Enameling upon Metals," should be used. The enamel should be ground until it is about the size of fine sand, and soft, not gritty, when rubbed gently between one's thumb and forefinger. It should now be rinsed in clean running water, the enamel being thoroughly stirred up and washed, the fine particles, "dregs" or "slimes" as they are called, being allowed to flow away. Often from ten to thirty per cent of the enamel is lost in this process. The remaining wet enamel powder is ready to be used. It may be kept for weeks under water in a glass jar or druggist's salve box, but in time is said to deteriorate. If the enamel is to be used immediately it may be placed upon a clean copper or china palette which will be found very serviceable. It should be kept constantly wet and if possible under water. If, however, it becomes dry, it may be washed as described above and will probably be found in good condition; if not a slight grinding may assist matters.

If enamel is not ground fine enough it is apt to have pit-holes in it when fired, and if it is not absolutely clean it is likely to have both pit-holes and black spots in it. Sometimes enamel is washed in nitric acid as well as water but this is generally not necessary. It is very important, however, to use water that contains very little iron, for iron will cause black spots in the enamel.

If enamel is to be kept for any length of time it should be kept either as chunks preferably or as coarsely ground powder. When coarsely ground it may be kept dry in a dirt-proof jar or bottle.

The "dregs" and "slimes" if washed clean may be kept and used for paints in painting on enamel.

When enamel is bought in the form of a powder it is generally necessary to grind it finer and wash it thoroughly.

PREPARATION OF THE METALS

MANY metals can be enameled, but the most practical ones, those most used in jewelry, are gold, silver, copper, and their alloys. Hence we will confine our descriptions to these metals.

Whatever metal is used, however, must first be made chemically clean before it is "charged" or covered with enamel. This may be done in a number of different ways, of which the following is considered the most practical.

The metal, whether gold, silver, or copper, must be annealed by being heated to a red heat and allowed to cool slowly in the air. When cool it will be found to be covered with a black oxide.

The metal must now be plunged for half a minute or more into a solution called a "dip," consisting of two parts sulphuric acid , two parts nitric acid , and a slight touch of hydrochloric acid ; a few drops of the latter to the gallon will suffice. This dip will clean the surface of the metal and make it bright. As the solution gets old it will become weak and a longer dip will be required. The ordinary commercial acids are suitable for making these dips. Care should be taken not to inhale the fumes of the acids, as they are quite poisonous.

This dip may be used cold, but better results are obtained when it is heated to 170?F. A convenient way to heat it is to set the jar containing the dip in a larger jar containing water and then to heat the water in the larger jar.

Many prefer to use first a hot and then a cold dip, rinsing the metal in clean water between the dips. Experience will soon teach one to tell when the metal is clean by looking at it, and this in fact is the only satisfactory way, as the length of time required will vary with the condition of the metals and the strength of the dip.

After the dip the metal must be thoroughly rinsed in clean water and then dried in clean sawdust or hot air. If rinsed in very hot water the metal will dry itself almost immediately. Some prefer to rinse the metal in ammonia as well as in water in order to rid it of all trace of the acid, but this is not generally necessary. If the metal is copper or gold it is now ready to be charged, but if it is silver it must be "fire-stained."

There are many other possible ways of cleaning metals, but the above means are generally used and will doubtless be found the most convenient. If small quantities only are being "cleaned," a copper pickle pan and a Bunsen gas burner will suffice, while for large quantities earthen pickle pots and large jars will be found advantageous. Metals if "wriggled," that is, scraped or engraved all over with a graver, are generally clean enough to be charged.

If silver is used it must be "fire-stained," or have the "fire" taken out of it. This is done in the following manner. The silver is submerged for a minute or more in a solution of four parts nitric acid and one part water, heated to 170?F. The acid will react on the silver, which will become covered with a brownish scum. The silver should now be rinsed in clean water and brushed with a metal brush in a solution of soap-tree bark and water. This will clean the scum off the silver and make the latter bright. After being rinsed in clean water, the silver is ready to be charged with enamel. Sour beer, or a solution of licorice root and water may be used instead of soap-tree bark. It will be very convenient to have the metal wire brush a circular one revolving on a lathe.

If red enamel is to be used, the metal should always be either wriggled or engine turned or else have some design cut sharply in it, in order to bring out the brilliancy of the color. Engine turning and sharp engraving or relief in the metal background will always enhance the brilliancy and give an additional sheen to any transparent colors. As the depth of the enamel layer has a great deal to do with the shade of the enamel, different effects can be obtained, even when only one enamel is used, if the metal background has been cut lower in some places than in others.

If the silver is not "fire-stained," red enamel will often become maroon when fired, and fondant and other delicate colors will become streaked or spotted. If the fire-staining and dipping have not been carefully done, the enamel is likely to chip out, have pit-holes in it, or contain black blotches.

As the acid fumes eat the flesh quite rapidly, it is advisable to wear rubber gloves when dipping the metals.

CHARGING

ENAMEL is "charged," or put on the metal, in the form of a watery mud, by means of a small spatula. The most convenient spatula is one made from a piece of steel wire about the size of a crochet needle and flattened at one end. In fact a crochet needle itself, flattened at one end, or even the small blade of a penknife, will be found quite serviceable. If this spatula is mounted in a wooden handle made from a penholder it will be found very easy to handle.

A small daub of very watery enamel should be taken on the end of the spatula and laid upon the metal where it is to be enameled. If the surface to be enameled is very large, a larger spatula can be used to advantage. If the enamel is too watery it will not stick to the spatula while being taken from the palette, and if it is too dry it cannot be readily transferred from the spatula to the metal.

When the piece has been entirely covered with enamel, it should be held in the hand and tapped gently with the spatula. If the enamel is wet enough this procedure will spread it evenly over the metal. The water should now be drawn off from the enamel by means of a clean piece of cloth or blotting paper. The remaining moisture will soon evaporate, leaving the enamel perfectly dry. Only when perfectly dry is it in a condition to be fired.

Care must be taken not to get the enamel on too thick, as in that case it will chip off when fired. On the other hand, enamel shrinks considerably on being fired, so if it is put on too thin it is apt to shrink, leaving bare spaces of metal. The proper thickness with which to charge a piece of work can only be learned by experiment, and in most cases it is desirable to charge a piece with several thin coats rather than with one thick one.

In cloisonn? and champlev? work it is generally necessary to use at least two coats in order to bring the enamel up to the level of the metal parts. Originally in these kinds of enameling the idea was to have each color or shade of enamel separated by a metal wall from every other shade, which made the charging comparatively simple. Now the vulgar modern taste permits several different shades side by side without partitions, or even blended. If the enamel is not too wet two distinct colors can be charged side by side without having them run into each other to any appreciable extent. They may then be fired, and they will be no more mixed in that process than they were before it.

A blend between two colors may be obtained by mixing two enamels together and then charging the piece with the mixture. Such a mixture when fired is often found to be speckled instead of a clear shade. If, after mixing, the enamel is ground finer, this speckled effect can sometimes be eliminated. This process is by no means always satisfactory.

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