5.1. Characterization of the wooden body
The radiocarbon results are consistent with a traditional practice of reusing a symbolic wood when making a qin, as explained in "Abiding with Antiquity", c.1860 . The radiocarbon dating results provide a significant hiatus, that could reach several centuries, between the dating of the wood in the [1458–1528] or [1552–1634] intervals and the dating of the silk string and red finishing lacquer in the [1659–1699], [1721–1814] or [1834–1848A] intervals (Fig. 6). The hiatus is relevant to the Chinese tradition which symbolically associates the material quality of "a very old paulownia wood" with the quality of the sound. This virtue of "antiquity" is cited in the "Twenty-Four Flavours of qin", ca. 1641, and detailed in the introduction by Goormaghtigh, as part of the aesthetic canons . Such a music appreciation is still controversially present in the modern practice of carving qin in a wood that has been stored for more than a hundred years . However, the storage of wood through several generations of qin makers is not attested in the past.
The dating hiatus between the wood on the one hand and the red lacquer and string on the other cannot be due to the sun-drying of a multi-century old tree trunk. The wood used to make the qin should be porous, light, even and smooth without the knots or distended and twisted fibers caused by the influence of the sun or the wind on the growth of the wood, as mentioned in early written sources. Therefore, secondary branches are preferentially selected according to an appropriate age and height . The Tang period poems (618–690, 705–907) studied by You  confirm the preference for secondary branches rather than the trunk, except in the case of a tree less than a decade old.
"As for the material that should be used, it should be from younger branches; that is, branches that are close to the top of the trunk. If the tong is not old, then its young branches will certainly not be big. Choose wood far away from the ground, with the top blown by wind and dried by sun. It should be moistened by frost and dew with plenty of pure air. Furthermore, it is good if the material is facing southeast, (because) "the Great Brightness (the sun) is born in the east".
The Book of Odes states: "The wutong grows there on those slopes and faces the sun" 
The interpretation of the 14C results as due to the reuse of wood is reinforced by the fact that the "Qiulai" qin is not made from a conventional paulownia species, but from a porous resinous wood from the Taxus family. Considering that the changes in Li Bai's poem carved on the back side are a subtle and skilful adaptation to this particular qin, the replacement of the sinogram tong 桐for paulownia by bai 柏for resinous woods of cedar or cypress may be linked to this manufacturing choice. Other wood species than paulownia can be used, especially old building timbers:
"As for good quality in old materials, (…) one cannot be certain that it will be tong wood. Some other kinds of wood are also all right. The wood is useable as long as it is light and porous, crisp and smooth. (…) As for beams, pillars, and router rafters, the ancients used tong for some of these. But it has to have survived for a couple of hundred years. If at an old monastery or temple on a high precipice or cliff, or by a waterfall, or stream shore in high, spacious and quiet regions, absolutely cut off from the cacophony of the everyday world, there one can find good material for the qin. Naturally it will have a special sound. "
As a testimony of this practice during the 19th century, the wood of the "Yun He" 雲龢 qin kept at the Musical Instruments Museum, Brussels (Coll. MIM, n° inv. 0760) has been identified as originating from Jing Hui 淨慧寺 Temple in the Guangzhou province (Canton) thanks to ink inscriptions on the back side . This unfulfilled epigraph also indicates that the qin was built by the maker Li Menggeng 李夢庚 whose life is poorly known, but who partly coincides meets the reign of Daoguang 道光帝 (1820–1850). The entry of this qin in the MIM collections is dated between 1881 and 1886 according to the inventories.
The 14C results for the wood of the "Qiulai" qin are consistent with a long tradition in qin making that consists in reusing old wood with a highly symbolic and spiritual value, whether during the period of activity of Tang Kai or in the early 19th century before the recorded presence of the qin in the CNAM collection in 1849.
5.2. Composition of the lacquer ash layer
The radiocarbon dating and material characterization of the "Qiulai" qin lacquer ash layer revealed a mixture of two major solid ingredients, bone black and malachite, consistent with the use of powdered deer antler and crushed stones mentioned in the Qinfang c.1641 and the Yuguzhai Qinpu c.1860 [3, 4]. The lacquer ash layer is located between the wood body dated from [1458–1528] or [1552–1634] and the red lacquer dated from [1659–1699], [1721–1814] or [1834–1848]. However, the heterogeneous 14C results on this layer are not compatible with the expected period of the making of the qin. Based on the material analyses, the age obtained might be due to the mixing of carbon from ingredients contemporary with the lacquering of the qin (F14C = 0.976 ± 0.007, value of the red lacquer) with 20% of geological carbonates from malachite residues (F14C = 0) remaining after acid etching during the chemical pretreatment of the sub-sample Q5-2.
The detection of carbon and phosphorous in the lacquer ash layer of the "Qiulai" qin does not differentiate deer antler ash from deer or another animal bone ash. Li et al.  also reported that the detection of Ca3(PO4)2 merely indicates the presence of bone ash regarding the "Yu Quan" qin from the Yuan Dynasty. However, traditional recipes comprising the raw sap of the lacquer tree and the ash of deer antlers lujiao shuang 鹿角霜 are mostly cited [14, 37]. According to the Yuguzhai Qinpu c.1860, "Whenever others put on the powder and lacquer they use a cattle horn comb (...). The powder; that is, deer horn shuang霜, (…) should be ground fine."
The detection of the coarse grains of malachite is suggestive of the qin makers’ practice of occasionally adding fragments of metal or stone to the lacquer ash layer in accordance with the symbolism of the carillon and lithophone so as to obtain the ideal acoustic properties, as discussed by Goormaghtigh  based on the following citation in the Qinfang c.1641: "The fingers struck the strings as if they drummed metal or stone, without any interference from the neighboring strings. It is in this search for limpidity that one goes beyond all sounds. ". Chang  mentioned that the highly estimated lacquer of qin made in the Tang Dynasty (618–690, 705–907) corresponded to the Asian lacquer technology consisting in adding scraps of metallic or stone fillers. A mixture, commonly named "eight precious ash" lacquer baobaohui 八寶灰漆 by qin makers, is made of fragments of gold, copper, bronze, porcelain, silver, mother-of-pearl, malachite, pearl, jade, agate, coral or seashells .
Powdered deer antler and crushed stones are not ingredients inherent to the qin but can be found in Asian lacquers . For example, a lacquered tray from the Ming period (1368–1644) presents surface "snake-belly cracks" as for qin from the same period, which could be due to the use of similar compounds such as powdered deer antler, bone, horn, ash, sandstone, or ceramics . Our results are consistent with the traditional composition of the lacquer ash layer of qin; however, due to the long tradition spread over several dynasties, a more accurate attribution is not possible.
5.3. The silk string and the red lacquer dating
The analyses revealed that the remaining silk string and the red lacquer are contemporaneous, meaning that the last lacquering and maintenance in playable condition occurred in China during the Qing dynasty (1644–1912) since the radiocarbon dating yielded the [1659–1699], [1721–1814] or [1834–1848] intervals. According to our investigations, three hypotheses are currently available for the attribution of the period when the "Quilai" qin that entered the CNAM collection before 1849 was built: i- it was collected, dated and signed by Tang Kai in 1712, ii- it was made by Tang Kai in 1712, or iii- it is a well-informed late 18th-19th century copy using an old wood carved in China.
The absence of typical cracks duanwen 斷紋 on the red lacquer is surprising. Cracks may begin to appear a hundred years after the making, and the shape of the cracks can be used for the relative dating of the qin. Re-lacquering or restoration of the "Qiulai" qin by successive owners can be considered during the [1721–1814] or [1834–1848] intervals, as such practices have already been observed on other ancient qin . For example, the "Mingfeng" 鳴鳳 qin is known to have been recut and re-lacquered by Tang Kai . The cracks on the "Xianren you" qin from the Song period (1127–1279) have been wiped out by restoration . However, the cracks are not necessarily proof of antiquity even if this is the reason why Chinese connoisseurs estimate them. Like the "Qiulai" qin, the "Yun He" qin that entered the MIM collection c.1880 presents no surface cracks either.
The "Qiulai" qin shows 18th-century features, and material characterization analyses as well as 14C results are consistent with the traditional practices of the qin makers from this period as described in written sources [3, 4]. The authenticity of this qin is credible. Indeed, the Qing dynasty period was rich in cultural exchanges between China and France under the Ancient Regime. French sinophilia during the 18th Century Enlightenment is also well-known under the reign of Qianlong (1735–1796). China’s tolerance toward Christianity allowed the establishment of Jesuits whose exchanges with the Académie Royale des Sciences provided information on Chinese techniques of the time. For example, the Jesuit Pierre Nicolas Le Chéron d’Incarville (1706–1757) sent a memoir to the Académie in 1760 mentioning the use of resin tree and calcined deer bones in black Chinese lacquers . The sending and the studying of qin in the eighteenth century in France is attested. For example, the Jesuit priest Joseph-Marie Amiot (1718–1793) sent a guqin to M. Bertin for his cabinet of curiosities , as reported in his correspondence with the Académie des Sciences : “The first is a Kin with seven strings, unlike those of today (…). It is made of a single piece of wood".
If the "Qiulai" qin was made by Tang Kai and kept its original lacquer, then it was manufactured in the [1659–1699] interval, since the 14C dating results on the red lacquer provide intervals that do not include the date of 1712 carved on the back side of the qin. The carving of inscriptions on a guqin traditionally took place after the instrument had been made and even played for several years.