However much trouble I have taken in informing myself as to the way in which the Chinese make porcelain, I am far from thinking that I have entirely exhausted the subject. You will see by the new observations I send you that fresh researches have given me fresh knowledge. These observations I will unfold to you without any order, just as I have put them down on paper as I have had opportunity, either in going through the workshops and instructing myself with my own eyes, or by asking different questions of the Christians who are occupied in this work.

Moreover, I will repeat nothing that I have already explained at length in my previous letter (which you have inserted in the 12th collection) and which it would be good to re-read carefully. Otherwise, one might find it difficult to understand many things, which I have assumed that you already know.

Although the gold applied to porcelain can be rubbed off with time or can lose much of its brilliance, one can restore its lustre by first moistening the porcelain with clear water and then rubbing the gilding with an agate stone. But one must take care to rub the vase in one direction only, for example, from right to left.

It is principally the edges of porcelain that are subject to chipping. So to avoid this problem, they are fortified with a certain amount of powdered bamboo charcoal, mixed with the glaze, which is applied to the porcelain (the powdered bamboo coals giving the glaze a pale grey color). Then, with a paint-brush, one makes a border with the mixture, on the already dried porcelain with the help of a potter's wheel. When it is time, the glaze is applied to the edge, just as on the remainder of the porcelain, and when it is baked, these edges are simply an extreme white. As there is no bamboo in Europe, I believe one could substitute willow charcoal, or better yet, charcoal of the elder, which is somewhat closer to bamboo.

Note that first, before reducing the bamboo to embers, the green skin is removed, as in the coals from this skin are sure to cause the porcelain to explode in the kiln; and that second, the worker takes care not to touch the porcelain with greasy or oily hands, as this will also cause the spot touched to chip on firing.

Speaking of colors that can be applied to porcelain, I said (in the 12th collection, p.307) that there was a red, blown onto the piece, and I explained the process. But, I remember that I omitted a blown blue color, which is much more successful. You have undoubtedly seen it in Europe. Our workers agree, that if money is no object, gold or silver could also be blown on porcelain, which could have a black or blue base. In other words, this would spread evenly a sort of gold or silver rain. This would be a new style of porcelain sure to please.

Other glazes can be blown, as well as the red. Not long ago, some pieces were made for the emperor that were so fine and delicate, that they were kept on cotton, because these pieces could not be handled without risking breakage. And as it was not possible to dip them in a glaze since that would have require handling them, the glaze was blown on, covered the porcelain entirely.

I remember that, while blowing the blue, the workers took care to save the color which missed the porcelain and to lose the least possible. To do this, they place the vase on a pedestal covered with a large sheet of paper which is used for a period of time. When the blue is dried, they reclaim it by rubbing the paper with a small brush.

A new material, suitable for making porcelain, has been found recently. It is a stone, a sort of chalk called hoa-che, which Chinese doctors use to make a kind of tea which is said to be cleansing, refreshing and somewhat of a laxative. They take six parts of this stone to one part liquorice and pulverize it. They put a half teaspoonful of this powder in a large cup of cool water which is given to the patient to drink. They clam that this tea refreshes the blood and reduces fevers. The porcelain workers have thought to use this same stone in place of kaolin, about which I spoke in my first writing (see p.273, of collection XII). Perhaps in a place such as Europe, where kaolin is not found, the stone hoa-che can be used. It is called hoa-che, because it is viscous and in a way resembles soap.

The hoa-che porcelain is rare and much more expensive than the other. It has an extremely fine grain and regarding work to be painted, it is to ordinary porcelain what vellum is to paper. Furthermore, the lightness of this porcelain surprises the hand used to other porcelains, also it is much more fragile than ordinary porcelain and it is difficult to predict the proper firing time. There are those who do not use hoa-che in their work, rather they make a somewhat thin glue of it, in which they dip the dried porcelain to coat it before applying the color and glaze. In this way, it acquires a certain degree of beauty.

Here is how the hoa-che is used. First when it is taken from the mine, it is washed in river or rain water to remove the attached yellowish dirt. Second, it is broken and put in a vat of water to dissolve, and then it is prepared in much the say way as kaolin. They assure that the porcelain can be made with hoa-che alone prepared in this way without any other addition. However, one of my neophytes who has made such porcelain says that to eight parts hoa-che, he added two parts of petuntse and kaolin. In this new kind of porcelain, hoa-che takes the place of kaolin, but the one is much more expensive than the other. A load of kaolin costs only 20 sous while a load of hoa-che costs a crown. So it is not surprising that this kind of porcelain sells for a lot more than the ordinary.

I will make another observation about the use of hoa-che. When it has been prepared and made up in small squares similar to petuntse, a number of these squares can be dropped into water to form a very clear glue. Then the paintbrush is dipped in and various designs are traced on the porcelain, after which, when it has dried, it is glazed. When the porcelain is fired, one can notice these designs, which are of a different whiteness than the remainder of the piece. It appears to be a thin vapor spread out on the surface. The white hoa-che is called an ivory white, siam-ya-pe.

Figures are painted on porcelain with che-kao (another mineral or stone), the same as with hoa-che, which produces another color of white. But che-kao is different, in that before it is to be prepared like hoa-che, it must be baked in a fire. Then it is broken, and is treated like hoa-che. It is thrown into a vat full of water, stirred and several times the floating mass is skimmed off. When this is done, a pure product is found and is used in the same way as the purified hoa-che. But che-kao cannot be used to form the body of porcelain. Up to now, only hoa-che has been found to take the place of kaolin, and to give solidity to porcelain. I am told that if more than two parts of petuntse to eight of hoa-che are added, the porcelain will collapse during the firing because it will lack strength or rather, that its elements will not be sufficiently well bonded.

I haven't spoken at all about a kind of glaze called tse-kin-yeou or burnished gold glaze. I would call it rather, a bronze-colour glaze, or dead-leaf or coffee color. This glaze is a recent invention. To make it, one starts with ordinary yellow earth, which is worked in the same way as petuntse. When this earth is prepared, only the thinnest part is used, and is thrown into water and forms a sort of glue, as liquid as the ordinary glaze known as pe-yeou (glaze made from blocks of stone). These two glazes – tse-kin and pe-yeou – are mixed and for this must be equally fluid. This is tested by dropping a piece of petuntse into the two glazes. If both the glazes penetrate the petuntse, they are considered to be of a like consistency and ready to be mixed. Some glaze of lime and fern-ash prepared as described elsewhere of the same consistency as the pe-yeou is also added to the tse-kin. But one adds more or less of these two glazes to the tse-kin depending on whether it is to be darker or lighter. This is learned by several tries. For example, one will mix two cups of the tse-kin liquid with eight cups of pe-yeou. Then, to four cups of this tse-kin-pe-yeou mixture, one cup of lime and fern glaze will be added.

They say it has only been about twenty years since they've found the secret of painting with tsoui or violet, and of gilding porcelain. A mixture of gold leaf with glaze and powdered stone has been tried, applied the same as the iron glaze but this endeavor has not succeeded and it has been found that the tse-kin glaze is more brilliant and charming.

It has been awhile since cups have been made with an exterior gold glaze and a pure white glaze inside. Next, a variation was tried, w here on a cup or vase, to be glaze in tse-kin, one or two rounds or squares of moistened paper were applied. Then the piece was glazed, after which the papers were removed and the unglazed spaces were painted red or blue. When the porcelain dried, it was glazed as usual, either by blowing or by another method. Some of these empty spaces were painted all black or blue in order to allow gilding after the first firing. There are also many other combinations imaginable.

This year for the first time, I was shown a type of porcelain which is very popular. It is an olive color, called long-tsiven. I have also seen some of tsim-ko, which is the name of a fruit which closely resembles olives. This color is made by combining seven cups of tse-kin glaze, four cups of pe-yeou, about two cup of oil of chalk and willow cinders and one cup of tsoui-yeou, a glaze made with stone. The tsoui-yeou makes many small veins appear on the porcelain. Applied alone, the porcelain will be fragile and will barely make a sound when struck, but when mixed with other glazes, it is intersected with veins, also the piece will ring and will be no more fragile than ordinary porcelain.

Brushing of better pieces.

I must add one peculiarity about which I haven't spoken and which I noticed just recently. Before glazing a piece of porcelain, they polish it and remove any imperfections, a process achieved through the use of a brush with very fine bristles. This brush is simply moistened in water and run over the piece lightly. However, this care is taken with only the finest porcelain.

Glossy or mirror black is called ou-kim, and is applied by dipping the piece in a liquid mixture composed of a prepared blue. It's not necessary to use a good blue, but it must be a little thick and mixed with some pe-yeou and tse-kin glazes, adding a little slip of chalk and willow-ash. For example, to ten ounces of powdered blue in the mortar, one adds one cup of tse-kin, seven cups of pe-yeou and two cups of oil of willow ash burned with chalk. This mixture is already a glaze, so none needs to be added. When this sort of black porcelain is fired, it must be placed near the middle of the kiln and not near the vault, where the fire is more active.

I was mistaken when I said (XII, page 302) that the red glaze – yeou-li-hum – was made of a red derived from copperas, such as is used in the red for refired porcelain. This glaze red is made from the shavings of red copper and a powder of a certain reddish stone. A Christian doctor told me that this stone was as a sort of alum, used in medicine. Both ingredients are ground together in a mortar, adding the urine of a young man and some pe-yeou oil. I have not been able to get the exact quantities, as the secret is well-kept and not let out. This mixture is applied to the porcelain before it is fired, and no other glaze is applied. Only, care must be taken that the red color doesn't flow to the bottom of the vase. I have been assured that when this red is to be applied to porcelain, no petuntse is used (in the porcelain), but in its place, some yellow earth, prepared in the same manner as the petuntse is used with kaolin. It is probably that such earth is more likely to accept this sort of color.

Maybe it would be convenient to learn how these copper shavings are prepared. We know that, in China, there is no coined silver. Bulk silver is used in business, and there are many pieces of an alloy base. However, there are occasions where they have to be refined as, for example, when a tithe or similar contribution is to be paid. Then, we have recourse to workers whose trade is refining silver in furnaces specially built for this purpose, at the same time separating the copper and lead. They form the copper shavings which, undoubtedly, still contain some invisible bits of silver or lead. Before the liquid copper coagulates and hardens, a small broom is dipped lightly in water and tapping on the handle, water is sprinkled onto the molten copper. A film forms on the surface, and is lifted off with small iron tweezers, and is plunged into cold water, where the particles form piece by piece. I think that if nitric acid were used to dissolve the copper, this copper powder would be more suitable for making the red whit I spoke about. But the Chinese don't know the secret of nitric acid and aqua regia, their inventions all being of extreme simplicity.

This year they made some ceramic designs which were supposed to be impossible. These were tall urns three feet and taller, plus pyramidal covers which add another foot in height. These urns are made of three pieces, but they are assembled with such skill and with such technique that they make one piece, so uniform that it is impossible to find the joints. I was told that eight urns were made, but that only eight of them were successful and all the others were lost. These pieces were ordered by some Cantonese merchants who dealt with Europeans, whereas in China, nobody is interested in such expensive porcelain.

I was brought to a piece of porcelain called yao-pien or transmutation. This transmutation happens in the kiln and is caused by either a defect or from excess heat or some other unknown cause. This piece which, in the opinion of the worker, was not successful, and was caused by pure chance, is no less beautiful or prized. The worker had planned to make soufflé red vases. One hundred pieces were lost and the one which I spoke of came from the kiln resembling a piece of agate. If one wanted to run the risks and the expense of different attempts, he could finally find the technique which chance produced only once. It is said that it was in this way that the mirror black glaze ou-lim was discovered. A furnace accident produced it and not it is made that way.

When one wants to apply a glaze which turns porcelain very white, to thirteen cups of pe-yeou he will add one cup of willow ash that is fluid as the pe-yeou. This is a densely colored glaze and should not be used on porcelain which is to be painted in blue, because, after firing, the color will not show through the glaze. A piece which has had the dense glaze applied can be exposed, without worry, to the kiln's strong heat. It is fired white as a monochrome or for gilding or for painting in different colors and re-firing. But when porcelain is to be painted blue, and the color is to appear after firing, only seven cups of pe-yeou are mixed to one cup of glaze or the chalk and willow ash mixture.

It is good to note that when the porcelain is coated with a glaze high in willow ash content, it must be fired in a cooler spot of the kiln, either behind the first three rows or a foot or afoot and a half off the floor. If it is placed too high in the kiln, the ash would melt quickly and would flow to the base of the piece. The same holds true for the red glaze, soufflé red and long-tsi-ven, because of the copper shavings used in these glazes (there are no copper shavings in long-tsi-ven – R.M.T.). On the contrary, a piece done only in tsoui-yeou must be placed high in the kiln. This is the glaze which produces the many veins, so that the piece appears to be made up of many pieces joined together.

There are some changes to be made in what I had previously said about the colors applied to the porcelain for the second firing. Before going into the details, it would be worthwhile to explain the measures of weight used in China, which is where I'll begin.

The copperas red used on refined porcelain is made in the way which I explained, with the copperas called tsao-fan. But, how is this glaze made? I shall explain that to you now.

To a tael or leam of ceruse (white lead), add two mas of this red. Sift the ceruse and red and mix them together dry. Then mix them together, using some water, containing a bit of cow glue sold condensed to the consistency of fish glue. This glue is used in painting the porcelain, to hold the red, so that it doesn't run. The colors, if applied too heavily, will produce an unevenness on the porcelain. This can be avoided by lightly dipping the brush into water from time to time, then back into the color which is to be painted.

To produce the color white, add three mas and three fuen of the clearest stones (powdered), to one leam of white lead. This is then burned, after being placed in a luted porcelain container, which is then buried in the gravel of the kiln, before heating the latter. This powder must be impalpable. Plain water is used, without the addition of glue, on adding the powder to the white lead.

Dark green is made by mixing one tael of white lead to three mas and three fuen of powdered stone with eight fuen or almost one mas of tom-hoa-pien, which is nothing more than the slag derived from melting copper. I have just learned that when using tom-hoa-pien to make green, it must be washed and separated carefully from the copper shavings so often found with it, since the latter is of no use of the making of green. Only the scales should be used, in other words, the parts of the metal which come loose when it is worked up.

As for yellow, to one tael of white lead add three mas and three fuen of stone powder and one fuen and eight ly of pure red (ferric oxide) which has not been mixed with white lead. Another worker told me that, to make beautiful yellow, he used two and a half fuen of unrefined red.

One tael of white lead, three mas and three fuen of powdered stone with two ly of blue make a dark purplish blue. One of the workers whom I consulted believes that eight ly of the blue are needed.

A clear aquamarine is made by mixing one part green with two parts white.

Mixing two cups of dark green to one cup of yellow makes a cou-lou green, similar to the color of a slightly withered leaf.

To produce black, blue is mixed with water until the resulting liquid is more or less thick. To this, add a little animal glue mixed with lime and cooked to the consistency of fish paste. When the porcelain to be re-fired is painted with this black, the black areas are then covered over with white. In the firing, this white mixes with the black the same as ordinary glaze mixes with the blue of common porcelain.

There’s another color called tsiu. This tsiu is a stone or mineral similar to Roman vitriol (a sulphate compound). According to the answers I get, I believe that this mineral comes from some lead mine and carries some kind of gases or rather, invisible particles of lead, such that it is easily incorporated into porcelain without the help of white lead, which is used as a vehicle for so many other colors.

It is from this tsiu that one makes a dark purple. It is found in Canton, and comes also from Peking, but the latter is definitely better. It is sold for one tael, eight mas per pound. Tsiu is melted and when it melts or softens, silversmiths apply it in the form of enamel to works of silver. For example, they mount a small piece of tsiu on a ring, or they put it on the head of a hairpin and use it for jewelry. This kind of enamel comes loose in time, but to get around this problem, a thin layer of fish glue is used to hold it in place.

Tsiu, as well as the other colors which I have spoken about is used only on pieces to be re-fired. This is how the tsiu is prepared: it is not baked like the blue, but is broken and ground to a very fine powder. It is then tossed into a vase of water, shaken a little, and the water is poured out, along with the impurities. The crystals which fall to the bottom of the vase are saved. This diluted mass appears a little ashy and no longer has its beautiful color, but tsiu gets back its purple when the porcelain is fired. Tsiu can be saved indefinitely. When one wishes to paint porcelain with this color, one only mixes it with water and a little animal glue if desired. This is often not necessary. This is all that I have been able to learn about this material. (Tsiu may be a manganese containing frit – R. M. T.)

To apply gold or silver to porcelain, add two fuen of white lead to two mas of gold or silver leaf, which has been dissolved. Silver over tse-kin glaze is very brilliant. If both silver and gold pieces are to be fired at the same time, the pieces in silver should be removed before the ones in gold. Otherwise, the silver will vanish before the gold had reached its shiny state.

There is a sort of colored porcelain here which commands a lower price than that which I have spoken about up till now. Perhaps the knowledge which I am about to pass on to you will be of some help in earthen ware, if you are not able to attain the perfection of Chinese porcelain. To make this kind of piece it is not necessary that the materials be very fine. One takes cups which have already been baked in the kiln but which are not glazed so they are all white and do not have a lustre. If one wishes them to be a single color one glazes them by plunging them in a vat of prepared color; but if one wishes varied colors such as the kind called hoam-lou-houan, which is divided into several panels, of which one is green another yellow and so forth. One applies the colors with a large brush. That is all the attention that one gives to this porcelain so it is only after firing that one puts a little red in certain spots as for example, in the mouth of certain animals but this color is not fired because it would disappear in the fire, also it (the red) is not very durable. When one applies the other colors, one re-fires the porcelain in the large furnace with the other porcelain that has not been fired but it is necessary to put it at the bottom of the furnace and under the vent holes where the fire is less active because a hot fire would destroy the colors.

The colors used for these types of porcelain are prepared in the following manner: to make green take some tom-hoa-pien, some saltpeter and some powdered flint (no one could tell me the correct proportions); then these are reduced separately to powders and are diluted and then mixed together in water. Commonly azure blue, together with saltpeter and powdered flint, forms purple.

Yellow is made by adding, for example, three mas of red copperas to three ounces of powdered flint and three ounces of white lead.

To make white, one tael of white lead is added to four mas of ground flint. All these ingredients are then diluted in water. This is as far as I was able to go into the color for this sort of porcelain since among my neophyte workers, there are none who use these.

When I spoke of furnaces where the new kind of painted porcelain is baked, I said (XXII, p. 311) that pieces are piled one on top of the other, small inside of large. I must add also, that care should be taken that the porcelain pieces don't touch each other on the places that are decorated, otherwise the pieces will be lost. You can put the base of one cup on the bottom of another because the edges of the bottom of the lower cup are not painted. But the cup sides must not touch; and when one has porcelain pieces that do no easily fit inside one another, as for example the tall cups fused for chocolate, our workers handle them in the following manner: Over a bed of these porcelain pieces spread out on the furnace floor a worker places a layer of plaques made from the same material as the kiln, or even broken pieces of porcelain, since, in China, everything is put to use. On the layer of plaques are placed more porcelain pieces, then another layer of plaques, etc., until the furnace is full.

I was not well enough informed when I said (XII p331) that the porcelain is done when the gold or the colors stand out in their brilliance. I realized later, on learning that the colors are only distinguishable on cooling, that I was mistaken. The porcelain is judged to be done firing when, looking through the opening on top: one sees the porcelain glowing red; the piled pieces of porcelain are distinguishable, one from the other; the porcelain no longer has the unevenness which the colors formed; and the colors are incorporated into the porcelain, the same as when a glaze applied to bleu blends with the latter.

As to the porcelain fired in the large kilns, the pieces are said to be done when: 1) the flame is no longer red, but rather a whitish color, 2) looking into the kiln, the plaques of porcelain used for piling are all red, 3.) removing a piece and allowing it to cool, shows the colors and glazes to be as desired, and 4.) looking into the kiln from above, the gravel on the bottom is glowing. The worker can judge the porcelain to be at perfection using all of these indicators.

When a worker wants the blue to cover a piece of porcelain entirely, he uses some leao, or prepared blue, diluted with water to a proper consistency, then he dips the piece in this preparation. As for the blown blue, tsoui-tsim, one uses the best blue, prepared as above, blows it on to the porcelain and when dry, paints it in ordinary glaze, either alone or with tsoui-yeou, if a crackled porcelain is desired.

There are workers who, over a blown or unblown blue, draw figures with the point of a long needle. The needle raises as many little points as necessary on the dry blue to represent the figure, then the piece is glazed. When fired, the figures appear painted in miniature.

There is not nearly so much work as one would imagine in pieces where flowers, dragons and similar figures are embossed. They are first traced with an engraving tool on the vase, then light cuts are made in the area, which gives them relief, and finally, they are glazed.

When I spoke in my first letter (XII, p.302) of the way in which leao or blue is prepared, I forgot two or three important particulars. 1.) Before burying it in the gravel of the kiln, where it is to be baked, it must first be washed to remove any attached dirt. 2.) It must be tightly closed in a well-luted porcelain box. 3.) After the blue is baked, it is broken, sifted and put in a glazed vase, into which some boiling water is poured. After having been shaken up a bit, the scum floating on top is removed and the water is poured off slowly. The process with the boiling water is repeated up to two times. Then, the resultant wet blue is reduced to a thin paste to be emptied into a mortar, where it is ground for a considerable period of time.

I was told that this blue is found in coal mines, or in the red earth in the vicinity of these mines. It can be found on the surface of the ground and this is a sure indication that by digging a little further in the same place one will find more of it. It is found in the mine in small pieces, slightly larger than one’s forefinger, but flat and not rounded. Ordinary blue is common, but the best is very rare and its quality is not obvious to the eye. It is necessary to test it if one is not to be fooled. The test involves painting it on porcelain and firing it. If Europe could furnish good quality leao (or azure) and good quality tsiu (which is a sort of violet), it would be a valuable commodity in Jingdezhen and easy to ship because of its small bulk; also one would be able to exchange it for the most beautiful porcelain. I have already said that tsiu is sold for one tael and eight mas per pound, that is to say nine francs. They sell the best leao for two taels per box of ten ounces, or twenty sous per ounce.

They have tried to paint some vases in black using the finest China ink (India ink). However this attempt was not successful. When the porcelain was fired it came out completely white. As the particles of this black did not have enough body, they were dissipated by the action of the heat. Or, rather, they didn't have the power to penetrate the layer of glaze or to produce a color different from plain glaze.

I finish these remarks, Reverend Father, by asking your prayers of the Christians of Jingdezhen, which is populated by a large number of porcelain workers. The Lord, who has entrusted their care to me bring some consolation each time I see their numbers grow. During a month's stay not long ago, I administered the sacraments to a large number of fervent Christians, and among those whom I baptized, there were nearly fifty adults. The progress of the Faith would be much greater if a missionary took up residence here. The church would need to be enlarged and there would have to be more catechists, but this would cost only a modest sum yearly. Perhaps some pious individual, who admires the beautiful works that Jingdezhen furnishes to all of Europe, would be zealous enough to consecrate a small portion of his wealth to the conversion of our workers.

Remember me in your prayers, etc.
d’Entrecolles, Mission of the Company of Jesus.