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What Is A Lacquer Tree And Where Do Lacquer Trees Grow

What Is A Lacquer Tree And Where Do Lacquer Trees Grow


By: Teo Spengler

Lacquer trees are not cultivated very much in this country, so it makes sense for a gardener to ask: “What is a lacquer tree?” Lacquer trees (Toxicodendron vernicifluum formerly Rhus verniciflua) are native to Asia and are cultivated for their sap. Toxic in liquid form, the lacquer tree sap dries as a hard, clear lacquer. Read on for more lacquer tree information.

Where Do Lacquer Trees Grow?

It is not hard to guess where lacquer trees grow. The trees are sometimes called Asian lacquer trees, Chinese lacquer trees or Japanese lacquer trees. This is because they grow in the wild in parts of China, Japan and Korea.

What is a Lacquer Tree?

If you read lacquer tree information, you find that the trees grow to about 50 feet tall and bear big leaves, each composed of 7 to 19 leaflets. They flower in summer, usually in July.

A lacquer tree bears either male or female flowers, so you must have one male and one female tree for pollination. Bees pollinate the flowers of Asian lacquer trees and pollinated flowers develop seeds that ripen in the fall.

Growing Asian Lacquer Trees

Asian lacquer trees grow best in well-drained, fertile soil in direct sun. It is best to plant them in somewhat sheltered locations since their branches are easily broken in strong winds.

Most trees of this species are not grown in Asia for their beauty, but for lacquer tree sap. When the sap is applied to objects and allowed to dry, the finish is durable and shiny.

About Lacquer Tree Sap

The sap is tapped from the trunk of lacquer trees when they are at least 10 years old. Cultivators slash 5 to 10 horizontal lines into the tree trunk to collect the sap that comes out of the wounds. The sap is filtered and treated before it is painted onto an object.

A lacquered object must be dried in a humid space for up to 24 hours before it hardens. In its liquid state, the sap can cause a bad rash. You can also get lacquer tree rash from inhaling the vapors of the sap.

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Lacquer Tree Information - Learn About Asian Lacquer Trees - garden

Lacquered objects are among the most highly treasured works of Asian art. Multiple, complex layers of lacquer are used to decorate the surfaces of screens, boxes, dishes, cabinets and small objects imparting a distinctive appearance that is also pleasantly tactile. With a history of production in Japan and China dating back to 5000 BCE, lacquerware began to be exported to Europe in the mid-16th century, where such objects were desired due to their uniqueness and great beauty. In the 17th century, European craftsmen began integrating panels removed from Asian lacquered screens into new pieces of furniture, which were then completed with panels that imitated the look and motifs of Asian lacquer, albeit using radically different materials and techniques. These European imitation lacquer techniques have been referred to as japanning.

The Characterization of Asian and European Lacquers project aims to develop a comprehensive analytical method to identify organic materials present in Asian and European lacquers.

Compositional and technological differences between Asian and European lacquers affect their aging behavior and long-term stability, which ultimately impact the lacquers' conservation. Scientific analysis of these lacquers could provide conservators with vital information about the composition and condition of the lacquer layers, aiding in the development of appropriate conservation treatments.

In response to these needs, scientists from the Getty Conservation Institute collaborated with J. Paul Getty Museum conservators to develop a methodology for sampling and analysis of the organic components of Asian lacquers and their European imitations that improves upon existing techniques both in terms of sensitivity and range of detectable compounds. Nine pieces of mid-18th century French furniture from the J. Paul Getty Museum that incorporate panels of Asian lacquer as part of their surface decoration served as case studies.

Research of the Characterization of Asian and European Lacquers project is divided into several components:

  • Development of a protocol for sampling individual lacquer layers
  • Development of an analytical protocol for detecting organic materials
  • Acquisition and analysis of reference materials
  • Study of Asian lacquered objects from the Getty Museum and other institutions
  • Compilation and evaluation of test data on European imitation lacquers.

In addition to aiding in the development of appropriate conservation treatments, the technical data from these case studies will be included among the information on these pieces in the forthcoming catalog of the Getty's permanent collection.

Project Background

Lacquer Formulations

The project began with a methodical literature review to determine the list of possible constituents for both European and Asian lacquers of the 18th century. For European materials, primarily 17th and 18th century sources were consulted however, for Asian techniques, we were forced to rely on 20th century texts in the hope that they accurately describe traditional techniques as practiced in prior centuries. It is worth noting that much of the Asian lacquer used in French furniture was made specifically for export, using techniques that varied from those used for higher quality domestic production. Therefore, modern descriptions of traditional techniques may not be representative of the materials in this study.

From our search of available literature we able to draw the following conclusions:

Asian lacquers consist largely of the sap from several trees within the Anacardiaceae family that grow throughout a number of specific geographical regions within Asia. The traditional lacquer known as urushi in Japan and qi in China is made from the sap of Toxicodendron vernicifluum. Vietnamese and Taiwanese lacquer is composed of laccol sap from Toxicodendron succedaneum. Burmese and Thai lacquer is composed of thitsiol sap from Gluta usitata. The three types of tree sap, composed mainly of substituted catechols which have long unsaturated side-chains, are toxic skin irritants.

Some form of pretreatment is required in order to convert the raw tree saps to a material suitable for application. For example, Kurome lacquer, the starting material in many Asian lacquer preparations, is prepared by heating and stirring the tree saps to reduce the initial water content to a low level. The working properties, appearance and cost of the formulations are modified by adding other organic materials to the Kurome lacquer such as drying oils, persimmon juice, shellac, animal glue, wood oil, benzoin and starch. Color is imparted by adding mineral and/or organic pigments. Each individual coat of Asian lacquer is cured first at high humidity (activated by a naturally-occurring enzyme) followed by air-drying. Lacquers on objects are built of multiple layers, often more than twenty.

In contrast, European japanning methods utilize varnishes that are highly complex mixtures of resins and oils, some of which may be present in small amounts. A few such products are resins from trees (colophony, sandarac, hard and soft copals, and elemi) and insects (shellac), along with organic colorants such as dragon's blood and gamboge. The materials are dissolved in an organic solvent and applied to the object, and the dry lacquer layer forms mainly by solvent evaporation, although lacquers with added drying oils require a certain amount of curing before a topcoat can be applied.

Analyzing Asian and European Lacquers

Successful characterization of these lacquers requires an analytical procedure capable of detecting even minor quantities of as many of the constituents as possible. Although separate procedures have been published for gas chromatographic analysis of Asian lacquer and of complex European furniture varnishes, the project team's desire is to develop a single analytical method capable of identifying and differentiating the components of both types of lacquer in one sample. This approach would streamline the analytical process and ensure that a minimum of sample material would efficiently yield a maximum of information.

One factor that limits the number of potential analytical tools for characterizing Asian lacquers is that the films are extremely intractable, being nearly impossible to dissolve in any type of solvent. Thus, the analysis must be carried out directly on the solid sample material. Pyrolysis-gas chromatography/mass spectrometry using derivatization with tetramethylammonium hydroxide (TMAH-Py-GC/MS) is the primary analytical method used. Heat and the TMAH reagent are used to degrade the intractable lacquer into small marker compounds that are characteristic of the original organic materials.

Presently, this technique requires approximately 50-100 micrograms of sample material for analysis, but the project team is conducting research to reduce the sample requirements. To test smaller samples, Fourier-transform infrared spectrometry (FTIR) is used and identification is done by matching the unknown spectrum to reference spectra of known materials.


Abstract

Positive-ion ToF–SIMS mass spectra of blended lacquer films of Japanese Toxicodendron vernicifluum and Vietnamese T. succedaneum in the following mass ranges: ( a ) m/z = 300−370 ( b ) m/z = 600−700.

Calibration curves of the compositional ratios of blended Japanese and Vietnamese lacquer films in accordance with the detected ion species using ToF–SIMS: ( a ) urushiol ion ( m/z = 313) and ( b ) laccol ion ( m/z = 347).

( a ) Py–GC/MS total ion chromatogram of blended Japanese and Vietnamese lacquer films ( b ) spectrum of peak U1 ( c ) spectrum of peak L1.

Calibration curves of the compositional ratios of blended Japanese and Vietnamese lacquer films in accordance with the detection peaks using Py–GC/MS: ( a ) urushiol peak (U1) ( b ) laccol peak (L1).

HPLC chromatograms of blended Japanese and Vietnamese lacquers including the following catechols: ( a ) 3-pentadecatrienyl ( b ) 3-heptadecyl.

Calibration curves of the compositional ratios of blended Japanese and Vietnamese lacquers as a function of standard catechol peaks using HPLC: ( a ) 3-pentadecatrienyl ( b ) 3-heptadecyl.


Lacquer Tree Information - Learn About Asian Lacquer Trees - garden

Eighteenth-century French furniture from the collections of the J. Paul Getty Museum decorated with Asian and European lacquered panels

Details of a commode, attributed to Joseph Baumhauer (JPGM 55.DA.2), showing the lacquered panels with the decorative gilded mounts removed

Historical map of regions in Asia where lacquer-producing trees grow

Harvesting raw urushi sap from cuts in the tree bark. Photo: Arlen Heginbotham, JPGM

Producing Kurome lacquer by heating and stirring raw urushi tree sap. Photo: Arlen Heginbotham, JPGM

Catechol molecules considered urushi marker compounds in Py-GC/MS test results of lacquers.

Imaging of objects with ultraviolet light and X-rays reveals details of the lacquer layers. This information helps conservators select the best locations to take samples. Photo: Arlen Heginbotham, JPGM

A corner cupboard by Bernard van Risenburgh II ( JPGM 72.DA.44)

Multiple layers are visible in this cross section, viewed under ultraviolet light, of a lacquered area from the Bernard van Risenburgh corner cupboard (JPGM 72.DA.44). Photo: Arlen Heginbotham, JPGM

Multiple layers are visible in the cross section, viewed under ultraviolet light, of a lacquered area from the BVRB corner cupboard, J. Paul Getty Museum accession number 72.DA.44

Arlen Heginbotham, JPGM Assistant Conservator of Decorative Arts, uses ultraviolet light to aid in removing samples of individual layers on lacquered furniture.

Michael Schilling, GCI Senior Scientist, examining a sample of lacquer under a stereomicroscope. Photo: Dusan Stulik, GCI

Placing lacquer into a pyrolyzer sample cup. Photo: Michael Schilling, GCI

Loading a sample cup into the pyrolyzer. Photo: Dusan Stulik, GCI

Pyrolysis-gas chromatography/mass spectrometry instrument in the GCI Science laboratories. Photo: Michael Schilling, GCI

TMAH-Py-GC/MS test results for Asian (bottom) and European (top) lacquers appear quite different.

TMAH-Py-GC/MS results for lacquer sample from the Baumhauer commode (JPGM 55.DA.2), show thitsi marker compounds present in several layers.

Marker compounds present in TMAH-Py-GC/MS test results differentiate the three types of Anacard lacquer

Herant Khanjian, GCI Assistant Scientist, using the Fourier-transform infrared microscope in the GCI Science laboratories. Photo: Michael Schilling, GCI

Identification of urushi in lacquer from the Bernard van Risenburgh red commode, (JPGM 72.DA.46) using FTIR analysis

As these samples from the GCI Reference Collection show, persimmon juice added to roiro urushi imparts gloss to the dry lacquer film. Photo: Arlen Heginbotham, JPGM

A selection of tree resin specimens generously donated to the GCI Reference Collection. Photo: Arlen Heginbotham, JPGM

Wood oil was discovered in Japanese export lacquer using TMAH-Py-GC/MS. Photo: Arlen Heginbotham, JPGM


FINDINGS: MATERIALS

As a wood-core lacquer sculpture, the Walters buddha’s core is made entirely of wood, with clay filler used in the lips, ears, textile folds, and possibly the eyelids. It is composed of twelve pieces of solid, carved wood pegged together with wood dowels and iron nails. [xiv] The back was hollowed out, providing a large cavity, which probably held dedicatory material. The wood panel that originally covered the cavity is now missing. There is no visible coating sealing the inside of the open wood cavity in the back of the Walters sculpture.

Both the Freer and Metropolitan images are hollow-core lacquer sculptures. They are hollow from the top of the head through the torso cavity and open on the bottom. Wood pieces are used for support in both buddhas, although not always in the same location. Both sculptures have narrow wood pieces enclosed in textile running around the interior edges of their bases, providing structural support to a location that receives much wear. Originally, the bottoms of both the Freer and Metropolitan buddhas were closed, but there is no evidence remaining of how this was achieved. These wood pieces may have aided in securing a cover over the open bottom. Some wood pieces are later replacements, but those wrapped in textile are original.

Additionally, imbedded in the textile of the Metropolitan image are three wood boards running vertically up the buddha’s back, acting as a spine. The Freer buddha does not have any wood in his back. However, the Freer buddha’s forearms are formed from two planks of wood butt-jointed just below the elbow. No wood was used in the arms of the Metropolitan image they are hollow.

X-radiograph of the Freer buddha

X-radiograph of the Metropolitan buddha (side view). Image courtesy Metropolitan Museum of Art

X-radiograph of the Walters buddha (side view). Image courtesy Walters Art Museum, Baltimore

The bodhisattva head does not contain any wood, but it is only a fragment of a much larger sculpture—nearly 7.5 feet tall if it was a seated image. [xv] No doubt wood was used to support certain areas of such a large sculpture.

The Freer and Metropolitan buddhas have vertical wood slabs in the back of their heads, incased in the textile layers (fig. S4). In X-radiographs, two large, horizontal nail holes can be seen penetrating the boards of both sculptures. The Metropolitan has the remains of two large iron nails in the holes. Two similar holes are present in the same location of the Walters buddha’s wood head. These were probably used to hold now-missing halos. All three buddhas have repairs covering the holes. The back of the head is missing from the bodhisattva therefore, we could not determine whether a halo ever existed.

The hands of all three buddha sculptures are missing. They would have been attached separately and made of either wood or lacquer with wire armatures in the fingers.

Both the Freer and Metropolitan sculptures have irregular holes (approximately 12 centimeters in diameter) in the middle of their backs (fig. S5a–c). These are probably robbing holes for the removal of dedicatory material. The hole in the Metropolitan buddha is off center, toward the right, avoiding the wood armature running up the back.

In the past, carbon 14 dating was carried out on wood from the Freer and Walters buddhas. [xvi] The results are broad (Walters: range of 420–645 CE Freer: range of 474–574 CE) because the size of the tree and the location where the sample was taken do not provide a date for when the sculptures were made, but rather for some point when the tree was growing. Additional carbon 14 dating on the textile or lacquer would give more accurate dates.

Clay core material

The development of hollow-core lacquer sculptures was an improvement over the wood-core lacquer technique. Without wood, objects became insect impervious, since lacquer is toxic. They were also very lightweight—the Freer and Metropolitan buddhas each weigh only about thirty pounds (13.6 kilograms)—with their hollow bodies providing space for depositing consecratory material. The Walters buddha, on the other hand, weighs more than twice as much.

To begin a hollow-core lacquer sculpture, an artist makes a clay core in the shape of the desired image. In the buddhas and the bodhisattva head, an internal armature likely was needed to support the clay during fabrication. Once a sculpture was nearing completion, the clay core and armature were removed, leaving a hollow shell.

The bodhisattva head is essentially a mask: it is completely open in the back, providing access for study. To determine the level of detail in the head’s original clay core, Smithsonian Exhibits made a 3-D scan of its interior and exterior (fig. S5). [xvii] Then, a positive print of the interior scan was created (fig. S6). It revealed that a surprising amount of detail was carved in the original clay core. Examination of the interior of the Freer and Metropolitan sculptures revealed that their cores were not as detailed, perhaps because of their smaller size, but it was not possible to scan the tight space.

All four sculptures have clay in between drapery folds and/or in noses, ears, lips, and eyelids to form fuller dimensions. Only the bodhisattva head still contains accessible clay clinging to the interior of the face, in the recesses of the lips, chin, and nose. A sample revealed it to be a gray-tan, unfired clay with a fine texture. The clay is uniform in particle size with no added organics visible in SEM images however, a large carbon peak was present in EDS spectra. The carbon is from the lacquer that was used to adhere the textile onto the clay (fig. S7a–b).

Textile and fibers

Once the clay or wood core of the sculptures was completed, it was covered with cloth strips wet with lacquer. The textile provided the dried brittle lacquer with more flexibility and strength. This made it more durable, helping to prevent loss of the lacquer, especially when the wood core expanded and contracted during changes of relative humidity. However, the movement of the wood does cause the lacquer to crack or fracture, especially over wood joins.

Strips of plain woven textile were dipped in lacquer and placed over the core piece by piece (fig. S8). Small individual strips allowed for more control over shrinkage or stretching of the textile than a larger piece of fabric would have. Cloth layers were built up and, when needed, additional strips were used to create folds in the drapery and enhance other details over the core. Where strip ends could be identified, no selvage was used. The ends and sides of the textile were often already frayed and unraveling when they were applied. Some locations have as many as six layers of cloth others only have two.

All four sculptures incorporated strips of plain weave textile of varying lengths. All sculptures have an S twist to the fibers. The thread count for each sculpture is:

  • Walters: 12 to 16 threads per square centimeter
  • Freer: 10 to 15 threads per square centimeter
  • Metropolitan: 10 to 12 threads per square centimeter
  • bodhisattva head: 8 to 12 threads per square centimeter
Identification of the hemp fibers was confirmed under the polarized light microscope. Here, the fiber is viewed under crossed polarized light with a gypsum plate. It is yellow when turned 90 degrees to the right.

The fibers from all four sculptures were identified by polarized light microscopy as bast fibers with crystalline nodes. The fibers’ colors further identified them as hemp when examined under polarized light using the first-order gypsum plate and compared with known samples (figs. S9–S10). [xviii]

In all of the sculptures, the textile was bulked with clay to form naturalistic folds in the robes. This is especially evident in the X-radiographs and CT scan of the Freer buddha (fig. S11). In the Freer buddha, EDS found aluminum between the textile fibers in the weave at the base of the lacquer, confirming that clay was used on the textile.

The structure was built in two phases for the hollow-core lacquer sculptures (Freer and Metropolitan buddhas and bodhisattva head). In the first phase, textile and lacquer were applied to the cores. The tops of the heads were either left open or cut off after this phase cured. Once the textile layers with lacquer were cured, the clay core was removed from the head through the top, providing access to the interior of the face. At this point, the eyes—including the third eye, now missing and filled in on all four sculptures—were set in. The bodhisattva has an additional cloth square applied over the back of the eyes. After work on the interior was complete, phase two began. The top section of the head was reattached or made separately and attached. The separate attachment is clearly seen on the interior of the sculptures and in X-radiographs but well-hidden on the exteriors. Then, more textile was added and, finally, lacquer layers (fig. 4a–c, fig. S12).

The interiors of all three hollow-core lacquer sculptures, originally in contact with the clay core, have a reddish-brown color to their textiles. In the bodhisattva, the reddish-brown material was applied as a liquid and pooled in some areas around the neck. A sample was taken from one of these areas (fig. S13) and the cross section imaged in both binocular and scanning electron microscopes (fig. S7a–b). GCMS identified lacquer and a protein glue in the sample. We found that the sample comprises three layers, which we then analyzed individually with Fourier transform infrared spectroscopy.

The first layer of the sample from the interior of the bodhisattva, the layer closest to the clay core, was the sole source of the protein seen in the GCMS analysis. This layer contains mostly residual clay from the core and soil, as confirmed by EDS, which found elements from clays: aluminum, silicon, magnesium, potassium, calcium, and iron, the source of the sample’s red color. [xix]

The bubbles in the third layer were formed when the lacquer was applied to the textile and air was trapped in between. The small amount of quartz, clay, and other particles found in this layer may have adhered to the lacquer coating before the textile was placed against the clay core. As there is interpenetration between the clay and the lacquer coating layer, the coated textile must have been applied wet. [xx] Certainly, it would have needed to still be wet to flexibly follow the clay core’s contours.

Low-power optical microscope mage of cross section

Backscattered electron image of cross section

Lacquer on the sculptures

Separate from the lacquer used to apply the textile to the clay core, lacquer was used to form the surface of the sculpture. All four sculptures we studied were made with Toxicodendron vernicifluum lacquer applied alone or with fabric in multiple layers. The lacquer structure in all four sculptures includes five types of layers: first, a lacquer coating on the textile to attach it to the core second, a thin lacquer layer above the textile coating to seal and smooth it third, a thick area of coarser material to provide bulk, composed of one to many layers fourth, a dark lacquer layer and fifth, final finish layers, either dark or light in color.

Image of the interior layers of the cross section under ultraviolet light

Image of the exterior layers of the cross section under ultraviolet light

A cross-section sample from the Freer buddha shows five lacquer layers above the textile (fig. S15) the same number is present in the Metropolitan buddha (fig. S16top, fig. S16bottom). In the sample from the bodhisattva (fig. S17), five lacquer layers are also present above the textile (layer C), followed by a layer of paint (layer I) and of soil (layer J). The Walters sculpture’s lacquer is more complex, with seventeen layers above the wood core, the most of all the sculptures studied (fig. S14).

Interior layers of the cross section under ultraviolet light

But if you look closer at the Walters cross section, there is an unusually uniform and sharp interface between layers F and G (fig. S20top, fig. S20bottom). It is also in a cross section studied in 1993 [xxi] that comes from a different location on the buddha. Particles at the interface appear cut, suggesting that it was polished before applying the next layer—a standard practice in lacquer production today. However, if polishing occurred between layers, why is this the only place where we see such a sharp line? There are a few possible explanations. It could indicate that the artists took a break during production, giving layer F time to become harder and causing it to keep its edge. This also would mean that the materials and techniques did not change in the layers above F, which is in fact the case: both the lower layers (F and below) and upper layers (above F) contain Toxicodendron vernicifluum lacquer, cedar oil, tannins, protein, and bone. An exception is the use of plant fibers or sawdust in the thick layer immediately above F however, similar plant fibers are seen in the other sculptures. There is a difference in technique in the upper layers. Thin, alternating light and dark layers were applied, and these account for the high number of layers on the Walters buddha.

Exterior layers of the cross section under ultraviolet light

A second explanation for the sharp interface is that it was polished to even out areas of loss and damage and prepare for a later reworking of the surface, with the layers above added during a restoration. The alternating light and dark layers in this case could indicate a restoration. If the upper layers were added later, the three or four layers below the interface (layers D–F, assuming no layers were lost) are fewer than the five layers seen in the other sculptures we studied.

While all four sculptures feature the five types of lacquer layers, there are many differences in how the lacquers were layered, as well as in the added components found in individual layers. The additives and inclusions in each layer are listed in tables 1–4 (table 1 | 2 | 3 | 4 ) and explored below.

Samples were removed from areas of loss on the four sculptures. Sampling location may have affected the results: different materials may be present depending on the area from which the sample was taken. For the Walters buddha and the bodhisattva, the samples were taken from areas of “flesh,” such as the upper back, while the samples removed from the Metropolitan and Freer buddhas were removed from the left drape edge. [xxii]

Lacquer additives: bone

When exploring the components of the lacquer, the most prevalent inclusion in all four sculptures is ground, partially burnt bone (fig. S19). It was clearly used as a filler to bulk up the lacquer and to form a paste. The bone particles were visible using microscopy, and their identification was confirmed by EDS in a scanning electron microscope.

X-ray maps, collected with EDS by scanning over the sample, show the distribution of different elements and were used to determine which layers contained bone. Figures S18a–d show X-ray maps for calcium, phosphorous, and silicon for the bodhisattva head sample. The overall brightness of the calcium and phosphorous maps indicate that finely ground bone is present throughout the cross section, and the large bright areas in the middle and near the surface of the maps are large bone fragments (up to 20 micrometer diameter) included in layers E and G. The sharp-edged particles of ground bone vary from light to dark in color depending on the degree to which the bone was burned.

In all of the sculptures, the bone fragments near the textile substrate are generally small, as would be needed to allow the lacquer to fill in holes and flaws in the textile and form an even surface. In the middle layers, the bone fragments are larger, as their primary purpose is to bulk up the lacquer. Toward the top surface, the bone fragments again decrease in size and amount as necessary to form a smooth surface that could be polished. The bone near the surface tends to be more uniformly burnt and black in color, possibly to blend with the darkened color of the lacquer that was colored by tannins and/or soot.

Ground burnt bone, although not common, has been used to bulk Chinese lacquer at least since the Warring States period (475–221 BCE): it was found in the lacquer layers of a cart in a tomb burial dating to that time. [xxiii] Bone could be ground into a variety of sizes, from coarse to fine particles. Bone powder particles are nonabsorbent, lightweight, and nonreactive to the lacquer resin.

Bone is composed of roughly 75 percent inorganic material and 25 percent organic material. Burning the bone would remove much of its organic components. However, residual proteins or other organics could help bond the bone to the lacquer matrix. It is clear that as one of the main ingredients, bone helped add body to the lacquer, creating a dough-like paste that made it easier to apply to vertical surfaces.

What kind of bone was used in these sculptures? Was it animal or human—perhaps the cremated remains of a monk? Attempts were made to answer these questions with DNA analysis. A sample of the Freer buddha was given to Robert Fleischer, research zoologist at the Smithsonian’s National Zoo’s ancient DNA laboratory. Unfortunately, he could not get a result, as the lacquer has its own DNA and the bone was partially burned, destroying most of the organic remains.

The protein in the lacquer was then analyzed via proteomics to determine the bone species. Timothy Cleland, physical scientist at the Smithsonian’s Museum Conservation Institute, ran the analysis and determined that the major source of bone protein in the bodhisattva lacquer is equid (horse or donkey), not human. However, since it is not possible to separate the bone from the remainder of the lacquer, further research needs to be done to determine whether other protein materials in the lacquer, such as animal glue, affected the proteomics results. Cleland also analyzed the source of bone protein in the Freer buddha and found it to be bovid (cow). [xxiv]

Lacquer additives: blood

A combination of cholesterol, protein markers, and trimethyl phosphate has been found in blood additives to lacquer. [xxv] Blood protein markers and trimethyl phosphate were seen in two of the lower layers of the Metropolitan buddha’s lacquer and in the upper layers of the Walters buddha. Protein markers for blood were also seen in a ground layer of the bodhisattva and possibly of the Freer buddha. It was also seen in two interior layers of the Walters buddha.

Blood may have been introduced as part of the bone or as a separate intentional additive. It was probably used as a binding medium. Blood is mentioned in several Chinese texts from as early as the Yuan dynasty as an additive for ground layers, and DNA analysis has revealed both pig and cattle blood in a ground layer of a tea box dated to 1820–50. [xxvi] [xxvii]

Through proteomics, Timothy Cleland found human blood in a sample from the bodhisattva. The sample contained all layers, so we do not know how the blood was added. This was unexpected and is still being explored.

Lacquer additives: tree resins

One organic additive to the lacquer formulation was a resin from trees from the family Cupressaceae or other fir trees, termed cedar oil here. This has been found in most lacquer layers of the Walters and two layers of the Metropolitan buddha. Several sources and forms of the material fit the chemicals identified by GCMS, so a specific source cannot be determined. There are several reasons why it may have been added: to act as an extender to cut the cost of the lacquer to affect the physical properties—either the working properties, such as ease of application or drying time, or visual properties, such as increased gloss or possibly as a preservative in the raw lacquer, as cedar oil has antimicrobial properties. [xxviii] A second resin, gum benzoin, was found with the cedar oil in the textile layer of the Metropolitan buddha.

Lacquer additives: oil

Oil was present as an additive to the lacquer in all four sculptures. It was not possible to identify specific oils used because, with the exception of tung oil, the fatty acids from the lacquers, bone, and waxes interfere in oil identification. However, the Metropolitan buddha’s lacquer likely has heat-treated (heat-bodied) oils. [xxix] Either cold-pressed or heat-bodied oil has been found in all periods of China. An early mention of heat-bodying can be found in a Northern Song dynasty document that mentions high and low temperature heating of tung oil. [xxx] Heat-bodying partially polymerizes the oils prior to use, resulting in a thickened oil that has lower shrinkage and is more durable after drying. [xxxi]

Lacquer additives: plant materials

Plant materials (such as sawdust) as well as small amounts of quartz and other silicates also are found in the lacquer layers.

In all four sculptures, several lacquer layers stained positive for starch, and starch was identified by GCMS. In some cases, positive staining for starch occurred specifically at the edges of fibers. This occurred in the textile layer of the Freer buddha (layer C) as well as interior layers with fiber pieces in the other sculptures. In the textile, starch at the fiber edge may have resulted in increased stiffness, as seen in a starched shirt today. More relevant for the cut fiber pieces, the starch may help strengthen the bond between fiber and lacquer, reducing the possibility of cracking. Starch could also have been used to thicken or provide more tackiness to the lacquer paste, or it could be coming from fibers or rice husks used as bulking materials in the layers. Plant materials weigh less than bone or silicates and would result in decreased weight—a plus for a self-supporting hollow sculpture, especially if portability was a goal.

Tannins, brown to black colorants that can come from several plant sources, were found in the Walters and Metropolitan buddhas and the bodhisattva. In addition, one marker compound for soot was found in upper layers of both the Walters and Metropolitan buddhas. At times, markers for compounds associated with specific plants used as dye sources (young fustic and old fustic) were seen in the GCMS results however, further research is needed to connect these markers solely with these plants.

Lacquer additives: glue?

The bodhisattva, the Freer buddha, and possibly the Walters buddha include layers, often lighter in color than the lacquer layers, where no Toxicodendron vernicifluum lacquer was found, but that contain proteins, most likely acting as an adhesive. Early texts advise the addition of protein glue to increase the adherence and durability of so-called ground layers. Markers for protein glue are also found in the lacquer layers of all four sculptures but the Freer buddha. However, while the bone fragments that are visible in the cross sections in many cases stained positive for proteins and are one source of the compounds seen with GCMS, glue cannot be ruled out as a component of the lacquers. Starting in the Northern Song dynasty, there are references to mixing lacquer and glue. [xxxii] Further research is needed to distinguish markers for bone from those for glue, as protein glue can be made from either boiled skin or bone.

Lacquer additives: wax?

We found remnants of prior conservation treatment in the analysis of the Walters buddha. Every layer contained elemi resin and beeswax. These materials were used along with paraffin wax on the entire sculpture to secure the flaking painted surface decoration. The museum’s records of the treatment [xxxiii] were critical in allowing us to separate the conservation materials from the original lacquer components. Still, it is not possible to tell if any waxes were among the original materials due to the presence of waxes from conservation treatment. The presence of the wax also interferes with our ability to identify the type of any oils added during production.

In the Freer buddha, wax was found in two interior layers as well as the textile layer. Since it is only in some of the layers, and those are on the interior, the wax may be original and not from a later conservation treatment.

Lacquer additives: miscellaneous materials

In addition to the materials discussed above, we identified a few miscellaneous materials in the sculptures. Cellulosic materials were found in the Walters buddha, the Freer buddha, and the bodhisattva, likely from chopped fibers or the hemp textile. Indigo was found in the Walters buddha.

Py-GCMS allowed us to identify many of the components added to the lacquer. However, there are others that could not be identified, as too little is present or their marker compounds are still unknown.


Bone, Flesh, Skin: The Making of Japanese Lacquer

In all lacquer objects, regardless of when they were produced, a resinous sap coating preserves the core material and allows for decoration. The material for lacquering is extracted from lacquer trees (Toxicodendron vernicifluum formerly Rhus verniciflua), which is the same genus as poison oak. The sap is collected by cutting the bark of the tree and scraping off the thick liquid in a manner similar to that used in obtaining latex from rubber trees. The highly toxic properties of this medium limit its use to specially trained, highly skilled artisans. The basic core materials for lacquerware are wood, bamboo, and animal hides however, lacquer can be applied to any surface as long as it can accept a primary coat of liquid lacquer, clay powder, and water mixture.

Lacquer must harden in a humid atmosphere, a process better described as “curing” than “drying.” One thin coat hardens overnight in a controlled atmosphere of 25–30 degrees Celsius (77–86 degrees Fahrenheit) and 75–85 percent relative humidity. Between each application, the lacquered surface must be polished. The artisan uses buffing materials that graduate from abrasive materials, such as charcoal, to softer media, such as a fingertip, used in the final polishing stages. After preparing the perfect surface, lacquerwares can be decorated with sprinkled gold or silver and inlaid mother-of-pearl and other materials. Producing a plain lacquered surface with a simple decoration is a lengthy, tedious, and often precarious process, since any mistake could ruin the whole piece.


What to know about Toxicodendron

Toxicodendron refers to a group of plants related to sumac. Most people know at least one of these plants by its common name, such as poison oak or poison ivy.

Toxicodendron plants produce an oil that is irritating and toxic to humans, and the plants may be most known for their ability to cause this reaction.

Touching the oil from one of these plants is enough to cause a strong allergic reaction in many people. The plants have little use because of this toxicity. So simply put, people should do their best to avoid them completely.

Keep reading to learn more about Toxicodendron, including the uses, risks, and dangers.

Share on Pinterest Poison ivy is one type of Toxicodendron plant.

Toxicodendron is a group, or genus, of woody plants in the Anacardiaceae family. The name comes from the Greek words for “toxic tree.”

The Toxicodendron genus includes a number of plants commonly known for their general toxicity, including:

  • Toxicodendron radicans (poison ivy)
  • Toxicodendron rydbergii (western poison ivy)
  • Toxicodendron toxicarium (eastern poison oak)
  • Toxicodendron diversilobum (western poison oak)
  • Toxicodendron vernix (poison sumac)

Some lesser-known plants of the genus include trees native to Asian countries such as China and Japan, including Toxicodendron vernicifluum (lacquer tree) and Toxicodendron succedaneum (wax tree).

These plants contain a few different oils. The oil urushiol may be the most well-known, as it is responsible for the severe allergic reaction from the plants. Touching the plants may cause urushiol to move onto the skin, leading to irritating symptoms.

Other plants, such as mango trees, also contain this oil. Picking mangoes or touching the leaves and branches can also cause skin irritation, but this is less common.

Many of the Toxicodendron plants have little applicable use given their high toxicity. However, some of the lesser-known plants do see regular use.

The following are some of the more common uses:

Lacquer

The T. vernicifluum tree, also known as the laquer tree, is a source of laquer in countries such as China, Japan, and Korea.

Tapping the lacquer tree produces a large amount of sap. Manufacturers then filter and heat this sap to produce a durable lacquer.

Interestingly, the lacquer is still highly irritating, as it contains urushiol. However, it is less likely to cause a reaction after drying and curing has taken place.

Candle wax

The production of laquer from T. vernicifluum and T. succedaneum creates a high fat byproduct that makes an alternative to wax.

Known as Japan wax or sumac wax, it is an alternative to normal petroleum-based candle wax and burns without smoking.

Cosmetics

Wax from the T. vernicifluum and T. succedaneum trees also makes its way into many cosmetic formulas, such as hair and skin creams. Manufacturers are much more likely to use the Rhus classification, which is an alternate classification for some plants of the genus Toxicodendron, for labeling purposes.

In its crude state, the wax has a rancid smell, which many manufacturers will process out. They will either sell the processed wax itself or other formulations containing the fatty wax.

Homeopathy

Some forms of Toxicodendron, such as Toxicodendron pubescens (poison ivy), make their way into homeopathic formulas. The Food and Drug Administration (FDA) do not evaluate homeopathic medicines, meaning that they are not regulated or widely available.

There is limited evidence for the use of a highly diluted version of poison ivy for certain symptoms, such as inflammation from arthritis. For instance, one paper notes that in laboratory studies, the diluted compounds helped control the inflammation response, which could help with symptoms.

More research is needed to focus on the effects in both animals and humans.

Although Toxicodendron plants have some limited uses, they also pose a risk to many people, including:

Allergic reactions

Toxicodendron plants can cause potentially severe skin reactions.

Though it is not technically a poison, urushiol oil can cause a severe allergic reaction in many people who simply touch the plants. This reaction is called urushiol-induced dermatitis.

A study in the journal Dermatitis notes that contact with these plants is the most common cause of allergic contact dermatitis in the United States. As many as 50–75% of the population are sensitive to the compounds in the plants, such as urushiol.

A reaction to this oil can cause symptoms including:

  • redness
  • swelling
  • pimple-like spots, called papules
  • blisters
  • streaks or abrasions in the skin

A person’s reaction to the oil can vary based on their individual sensitivity to it, as well as the contact duration.

Although some forms of allergic reaction clear up quickly once the irritant goes away, a Toxicodendron reaction can linger. For example, it can take 3–4 weeks after the first exposure for the symptoms to subside and the skin to return to normal.

In some cases, the reaction can even cause permanent scarring. This may be more likely in people with severe reactions who scratch their skin, leading to open sores or longer healing times.

Although reactions to urushiol can be painful, not everyone will have them. People vary in their sensitivity to urushiol. Some people may have little or no reaction when touching the plant, while many others can have very severe reactions from even small amounts of contact.

Contamination

Urushiol comes off of the plant very easily, especially when a person breaks the leaves, stems, or branches.

This does not only apply to the skin, however. In fact, urushiol can also contaminate a number of other common objects, such as:

  • clothing
  • shoes
  • walking sticks
  • gardening tools
  • towels

Additionally, if a person has this oil on their skin, it is possible to pass it to another person who touches the affected skin. Pets can also have the oil on their skin and share it with humans, or they might even have a reaction themselves.

Washing the affected skin should help strip away this oil and stop it from being contagious. Washing is also an important part of treatment, as urushiol is an oil that adheres to the skin.

As soon as a person notices any contact with one of these plants, they should wash the affected area vigorously with soap and hot water. Although there are specialized products designed to remove urushiol, a study in the Journal of the American Academy of Dermatology notes that simply washing is the most important treatment and prevention method.

Thoroughly washing any items that have touched the plants should also help remove the oil and prevent a reaction.

The safest route is to simply avoid contact with Toxicodendron plants and any items that may have touched one.

Misidentification

There is also a risk of people traveling in areas where these plants grow and misidentifying them. For instance, though it is not related to oak in any way, poison oak grows in a similar way as white oak and has a similar appearance.

Anyone who lives or hikes in areas where Toxicodendron plants grow should familiarize themselves with the specific types in their area and how to identify them. This can help prevent accidental contact and potential allergic reactions.


Watch the video: What is Lacquer Artwork