Jadeite optimization treatment and identification characteristics, collection for future reference

The heat treatment of jade is mainly aimed at yellow, brown and brown jade. By heating, its oxidation is promoted, making it turn into bright red. It is worth mentioning that heat-treated jade has the same durability as natural red jade.

Because the formation is basically the same as that of natural red jadeite, the only difference is that heating accelerates the water loss process of limonite, causing it to turn into hematite in the furnace. In terms of appearance, natural red jade is slightly more transparent, while heated red jade feels dry. The basic characteristics of heat-treated jade are basically the same as those of natural jade, so it is not easy to identify by conventional methods.

So, how to identify heat-treated jadeite?

Through infrared spectrometer identification, it can be seen that natural jade shows strong absorption areas near 1500~1700cm-1 and 3500~3700cm-1, which are the absorption areas of microcrystalline water and adsorbed water; heat-treated jade does not have strong absorption areas at the above two positions. This shows that there is no water in the fired jade.

Jade wax treatment

Wax dipping of jadeite means putting the finished jadeite into liquid wax, slightly heating and soaking it, so that the wax liquid can penetrate along the cracks and tiny gaps. After polishing, it can increase the transparency of the jadeite and cover up the original gaps.

This treatment method only temporarily covers up the more obvious cracks, increases the refraction and reflection ability of light, and improves the transparency. If it encounters high temperature, the wax will overflow and the durability will be poor.

Key points: Wax treatment is a common process in jade processing. Mild wax treatment does not affect the gloss and structure of jade and is an optimization. Severely wax-impregnated jade can be seen with blue-white fluorescence under ultraviolet fluorescent light, and the fluorescence characteristics of organic matter are very obvious, with characteristic spectra of 2854cm-1 and 2920cm-1.

Bleaching and filling treatment of jadeite

There are two types of bleaching.

The first bleaching treatment is one of the commonly used methods in traditional jade processing, which is called "over-sour plum". The purpose is to remove the discoloration on the surface of jade without affecting the durability of jade. It belongs to "optimization" and is still in use. What we call bleaching today means placing jade in strong acid to destroy the original structure of jade and bring substances in and out. This type of bleaching belongs to "processing".

During the bleaching process, while removing the impurities and dirty colors, the original structure of the jade is also destroyed, causing more and larger cracks to appear between the jade particles, some of which even appear to be loose, slag-like. Such jade cannot be used directly, so some organic aggregates that can play a consolidating role must be used to fill the gaps. This not only consolidates the jade but also increases its transparency. This process is called "filling".

The internal structure of bleached and filled jade is damaged to a certain extent, and the gelatinous solids will age after a period of time. The gloss, color, "water head", etc. of the jade will change, affecting the durability of the jade.

So, what are the identification characteristics of jadeite that has been bleached and filled, the so-called "B-grade"? Today, I will introduce to you some common identification methods.

1. The gloss becomes weaker

2. The color distribution is very unnatural

3. Under transmitted light, the criss-crossing cracks inside can be seen; under reflected light conditions, the dissolution pits and spider-web-like patterns on the surface are clearly visible.

4. The density and refractive index of most bleached and filled jadeite are slightly lower. The density is 3.00~3.43g/cm3, and the refractive index is about 1.65 (point measurement). Due to the complex mineral composition of jade, the density and refractive index values ​​of some natural jade may be low, so the density and refractive index can only be used as a reference and usually cannot be used as a basis for determining whether jade has been filled.

5. The fluorescence intensity is weak or there is no fluorescence, and the fluorescence distribution is uniform or mottled.

6. When “B-grade” jade is heated to 200-300℃, the gum will carbonize.

7. After bleaching and filling, the mineral particles of jade are filled with gum. Therefore, it makes a dull sound when tapped lightly, which is significantly different from the crisp sound of natural jade.

Dyeing of Jadeite

Dyeing is the most primitive and easiest method of jade processing. Jade used for dyeing must have certain gaps to facilitate the colorant to enter the cracks for dyeing.

Dyed jade has poor durability. Since the colorant does not enter the crystal lattice but exists in the cracks, when the colorant is exposed to light for a long time and oxidized by air, the originally bright color will fade or even become colorless.

How to identify dyed jadeite?

1. Magnify and inspect. The color of dyed jade is distributed in a silk screen pattern.

2. Spectral characteristics. Green jadeite dyed with chromium salts often shows an absorption band 650mm wide, which is strong evidence for identifying dyed jadeite.

3. Charles filter. Due to different colorants, dyed jadeite reacts differently under the Charles filter. It can remain unchanged or turn red. But if the green jadeite turns red under the Charles filter, it means that the jadeite has been dyed.

4. Ultraviolet fluorescence. Some dyed jade will emit yellow-green or orange-red (dyed red jade) fluorescence under ultraviolet light.

5. Infrared spectrum. Jadeite dyed with organic dyes will show absorption peaks at 2854cm-1 and 2920cm-1 in the infrared spectrum, which indicates the presence of organic matter in jadeite.

6. Extremely negative luminescence microscope. The fluorescent colors are mainly blue-green, yellow-green and other colors.

Jade coating treatment

Coating treatment refers to covering the surface of the finished jade product with a layer of organic film to change the color of the jade. This kind of jade is also called "dressing jade".

The durability of coated jade is poor and the film is easy to fall off. This kind of jade has uniform color; its refractive index is low, about 1.56 by point measurement (refractive index of the thin film); under magnified observation, it can be seen that its surface gloss is weak, mostly resin gloss; there is no granularity; bubbles can be seen in some parts; if you look closely at the edges, you can see that the film has fallen off; it feels soft when touched with a needle; and it feels astringent.

fcgc66

fcpf18