|Carved lacquer has oil added - according to this research|
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It is interesting to note that Chinese craftsmen who produced carved lacquer may have taken conscious advantage of the softness and slower curing of lacquers mixed with oils. Lacquer that is to be carved must not be so hard and brittle that it is prone to chipping and breakage during carving. Because lacquer can continue to polymerize over a period of weeks and months after initial curing (Webb, 2000 Webb, M. 2000. Lacquer Technology and Conservation: A Comprehensive Guide to the Technology and Conservation of Asian and European Lacquer. Oxford: Butterworth-Heinemann.
, p. 8), it can become progressively harder and more brittle over this timescale. From the carver's point of view then, it is critical that the prepared lacquer substrate not harden too much before the carving is complete or else the work will be ruined. It would seem that a traditional manner of preventing premature hardening has been the addition of significantly more oil to the lacquer than is customary in flat lacquer production. To date, we have only been able to analyze samples from seven objects of Chinese carved lacquer, dating from the fifteenth to eighteenth centuries. These objects include a variety of types, from Ming imperial ware to an eighteenth-century bowl from Yunnan to export ware from the southeast. Nevertheless, each of these pieces has in common a very high proportion of oil in the formulation. In most cases, the combined fatty acid peak area comprises more than 90% of the sum of all analyzed compounds while the Anacard components typically total only 3–7% of peak area. These proportions are quite unusual in flat (uncarved) lacquer that the authors have analyzed.
[LATER: A YouTube video mentions that the lacquer tree sap is mixed with 50% oil. Tung oil seems a likely candidate to me, as it's a traditional Chinese oil.]