In the history of Chinese ceramics, a red color rich in copper oxide was first created and used in the 14th Century, in the kilns of Jingdezhen, a city in the Zhejiang Province, not far from the Chang River, in the central part of China. The copper-red colored ceramic production was stopped at the age of the Emperor Zhengde (1506-1521 B.C.), to reappear in the late 17th to early 18th century, during the reign of Emperor Kangxi (1662-1722 B.C.) of the Qing Dynasty.
The porcelain production in monochrome copper-red characterized the Qing Dynasty, (1644-1912), but reached its perfection technical under the Emperors Kangxi (1622-1722), Yongzheng (1723-1735), and Qianglong (1735-1796). During the Kangxi reign, talented supervisors controlled and improved the quality of official imperial porcelains. Lang Tinji, one of these professionals, was in charge from 1705 to 1712. He is believed to have linked his name to the so called “Lang-yao,” i.e., “Lang wares,” which included white and blue porcelains in the Ming style, and unsurpassed copper-red monochromes. 
During the second half of the 19th century, copper-red monochromes became highly desirable products for many Europeans. They became so popular among European dealers and collectors that they were given the name sang de boeuf (i.e., “ox blood”) by E. Grandidier.  By the early Qing Dynasty, the colorant did not contain any traces of iron (another metal providing red coloration), but only copper, a fact that caused great difficulty in keeping the underglaze pigment during firing, due to the volatility of copper. Skillful handling of pure copper firing made it possible to obtain wonderful red monochrome glazes. In the kiln, copper-red porcelains were fired in a reducing atmosphere. The red color appeared quite late, only during the cooling phase. 
During the Qing Dynasty, especially during the Kangxi reign (1644-1912), red glazes on the porcelain body were characterized by uneven distribution, and that fact enhanced quite considerably the fascination of the object. In high-quality porcelain the rim of the vase is usually white, as is the glaze of the inner surface of the vase. From the white mouth, the color of the neck gradually transforms into pink, creating subtle vertical streaks (Fig. 1), and then turns into a deeper red tone at the globular part of the vase (Fig. 2). Under magnification and under tangential light, the red glaze is seen to be the result of extremely subtle specks floating in the brilliant, transparent glaze on the surface of the body. These effects are the result of copper compounds, and to the chemical and physical reactions during the reduction process in the kiln.  In particular, the smaller copper particles become yellow, the larger ones become red, and the largest turn to green.
The neck of this Lang-yao copper-red vase with a white rim is covered with a crackled pale pink intermediate zone, striated by red vertical, parallel streaks. Kangxi reign (1662-1722). Private collection, Italy.
This large Lang-yao copper-red bottle vase is of large globular shape, with a slightly tapering neck, and a body covered with a rich deep red glaze. The glaze thins to paler tones towards the neck and the mouth rim (40.5 cm high). Kangxi reign (1662-1722). Private collection, Italy.
The proper handling of the reduction process was crucial to obtain the wonderful red of the so-called sang de boeuf. The red copper color was considered the most difficult to control and to obtain.
The type of copper-red known as sang de boeuf has to be distinguished from other types of copper-red glazes. One type is called in Chinese “sacrificial” or “massed red.” It is characterized by a uniformly coral-red lustrous tone and by a low content in copper. Other types are the “peachboom” glazes, containing up to four times as much copper, and whose variegated effect in the nuances of pink, gray, and greenish was caused by the presence of metallic copper in the stratified layers of the coats of glazes and not to copper oxide. The third type of copper-red glaze is known as the “flambé“ or “flamed” variant of glaze, produced by the appearance of bluish-white streaked effects during the firing process in the kiln, linked to the presence of lead. The final effect of “color-splashed flamed” glazes was originally and properly termed in Chinese as “yao-bin,” i.e., “furnace transmutation,” or “changing of color in the kiln.” The streaked effects, or better the “splashed effects” in later decades of the 18th century, and specifically during the Qianglong reign (1736-1795), were “helped along,”  covering the biscuit with uneven thick walts coating of copper, or adding other minerals. It is now known that the earliest wonderful flambé effects during the Kangxi reign (1662-1722) were obtained just by accident. 
Coming now to the field of medicine, and more specifically to dermatology, it is known that, as we can distinguish different types of copper-red glazes in the history of Chinese porcelain, red streaks may be observed in a spectrum of inflammatory diseases involving, for instance, glans penis and mucosal surface of prepuce. These striated patterns include angiokeratoma corporis diffusum,  hemorrhagic events, such as vasculitides,  lichen sclerosus et atrophicus, and drug induced disease, as in the case presented here.
Report of a case
A 62-year-old Caucasian uncircumcised patient presented himself to us with a reddish moist patch on glans penis and prepuce that had appeared suddenly and persisted for as long as 10 days (Fig. 3).
Reddish moist patch on glans penis with red subtle vertical streaks.
A 3 mm punch biopsy was taken under local anaesthesia from the glans penis. Neither bacteria, fungi, nor Candida albicans grew in cultures. The patient told of moderate pruritus. Histopathology revealed atrophy of the epidermis and a dense lichenoid infiltrate of lymphocytes and plasma cells in the upper part of the dermis. There were numerous extravasated erythrocytes and siderophages.
The history of the patient revealed a previous surgical intervention for mitral valve prolapse, two months earlier. One week after surgery, the patient suffered from acute dyspnea associated with anemia, caused by a massive hemorrhagic pleural effusion. Since that time, the patient had been under treatment with warfarin. The patch on the glans was relatively well circumscribed, sparing the area surrounding the urethral meatus. The lacquered, moist patch was characterized by subtle, vertical, parallel, reddish to purpuric streaks. The prepuce mucosa was characterized by the presence of a uniform hemorrhagic plaque (Fig. 4). Since warfarin could not be discontinued, glans and prepuce involvement were persistent, with periods of remission due to short courses of topical steroids.
Ventral surface of prepuce is characterized by a well-circumscribed non-blanching, nontender, purpuric plaque.
Purpuric nuance on the glans of the penis has been reported, albeit as a rare finding, in balanitis circumscripta plasmacellularis [8 ] with histopathologic evidence of deposits of hemosiderin in the dermis. In a clinico pathologic study of 45 cases of balanitis of Zoon, [9 ] Weyers et al. reported that extravasation of erythrocytes may be seen in 44.4% of cases, and siderophages in 24.2% of cases. Hemorrhagic Henoch-Schonlein purpura involving the glans penis in a 4-year-old boy has also been reported, without histopathologic report (Fig. 5). [7 ]
Histopathology is characterized by atrophy of the epithelium, a dense lichenoid infiltrate, made up of lymphocytes along with plasma cells. Numerous extravasated erythrocytes and siderophages are also present. H&E.
Our case may best be diagnosed as a manifestation under the wide umbrella of balanitis of Zoon, but with a peculiar appearance clinical typified by fine streaks and a presumed relationship of the lesion to warfarin treatment. This case demonstrates that the red color clinically is caused by the presence in number of extravasated erythrocytes in the dermis. Siderophages seemed to have appeared rather quickly in a relatively early phase of the lesion, that is, within ten days.
In dermatology, there is a long tradition of comparing clinical features of a lesion or of a disease to the color or to the form of a thing entirely unrelated to the skin but known more widely. Some examples are reported in Table 1. Along with this tradition, the subtle reddish streaks of the Lang-yao Chinese porcelain may help in recognizing and properly describing clinical lesions such as those in our patients in whom hemorrhage causes subtle reddish streaks reminiscent of those encountered in the Chinese porcelain.
Table 1. Only few examples, among the numerous ones in the dermatologic semantic system, of referring diseases or signs of a disease to a color, a form, or an object commonly well-known outside medicine.
|Coppery red papules||Secondary syphilis|
|Port-wine stain||Capillary malformation|
|Salmon patch of the nape of the neck||Nevus simplex|
|Café au lait spots and macules||Neurofibromatosis|
|Strawberry tongue||Kawasaki disease|
|Bamboo hair||Netherton syndrome|
|Ash-leaf spots||Tuberous sclerosis|
|Cayenne pepper grains||Schamberg’s disease|
Giovanni Borroni, M.D., is chairman of the Institute of Dermatology at the University of Pavia, IRCCS Policlinico San Matteo, Pavia, Italy, where Camilla Vassallo, Ph.D. Michela Castello, M.D., Raffaello Cananzi, M.D., and Olga Ciocca, M.D., are residents in Dermatology from the Department of Human and Hereditary Pathology at the same university. Contact corresponding author via email: firstname.lastname@example.org.
1. Zhongguo taoci shi: 417-718 (quoted by R. Kerr, 1998 ).
2. Grandidier E. La Ceramique Chinoise. Chinoise. Ed. Firmin Didot, 1894.
3. Kerr R. Chinese ceramics. Porcelain of the Qing Dynasty 1644-1911. London: Victoria and Albert Museum Publ, 1998.
4. National Palace Museum, Taipei. Catalogue of a Special Exhibition of the Ching Dynasty Monocrome Porcelains in the National Palace Museum. Taipei: National Palace Museum, 1981.
5. D’Entrecolles FX. Letter of the 25th January, 1722 from Jingdenzhen to Father Orry. In: Lettres edifiantes et curieuses. Ed. Le Gobien C and du Halde JB. Paris, 1722.
6. Mc Kee PH. Pathology of the skin with clinical correlation. London: Mosby-Wolfe, 1996.
7. David S, Schiff JD, Poppas DP. Henoch-Schonlein purpura involving the glans penis. Urology 2003;61:1035xiv-1035xv.
8. Davis DA, Cohen PR. Balanitis Circumscripta Plasmacellularis. J Urol 1995;153(2):424-426 .
9. Weyers W, Ende Y, Schalla W, Diaz-Cascajo C. Balanitis of Zoon: a clinicopathologic study of 45 cases. Am J Dermatopathol 2002;24(6):459-467.