On December 14th, 1600, the ship San Diego, prepared to carry out the route and the trade mission of the so-called “Manila Galleon”, sank off in front of Fortuna, a small Philippine island close to Manila, as a result of a Dutch attack, dragging up to 50 meters all its load. Almost four centuries later, the wreck was excavated in 1992 and 1993, which revealed that this shipment included a magnificent set of 1200 pieces of blue and white Chinese porcelain, mostly from Jingdezhen kilns, and about 800 jars, pots, lamps and vessels from the Southeast Asia (Burma, Thailand and the Philippines) that kept marks of workshops, potters and owners, and showed the importance and regularity of trade between Manila and Acapulco. A part of these objects was deposited in the Naval Museum of Madrid, were they are currently exhibit in a monographic room.
Most of these ceramic containers transported commodities of a very diverse nature and origin. Accordingly, the study of their technical characteristics and provenances results of extraordinary importance to know trade routes of that time to thereby trace some historical precedents of globalization. The archaeometric characterization results of a representative selection of potsherds is here presented, either of productions from Asian origin, commonly known as the Martaban type, or the so-called in Spanish “olivareras” (olive jars) from Andalusian origin.
To carry out the archaeometric study, the following chemical-physical characterization techniques were used: binocular magnifying glass, petrographic observation of thin sections, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray microanalysis (EDS), and X-ray fluorescence spectrometry (XRF). The chemical composition data obtained by XRF were later study by multivariate statistical techniques such as principal component analysis.
Resulting data showed that Asian type and Andalusian type ceramics are very different both in chemical composition and in technology of production. While Andalusian type ceramics were elaborated from calcareous clays, Asian type ceramics were produced with non-calcareous ones. In addition, glazes or enamels used to waterproof the surfaces of the ceramic containers were also very different since it was found that lead rich enamels were used in Andalusian ceramics while alkaline-earth enamels probably from plant ashes as flux agent were employed in Asian ceramics. The Andalusian ceramics were approximately fired at equivalent temperatures between 1100 and 1150 °C. On the contrary, the Asian type ceramics were fired at equivalent temperatures higher than 1300 °C, so they are materials that can be classified as stoneware. Finally, the mechanisms of ceramics alteration, which have been submerged in the marine environment for more than 400 years, have been also observed and studied.