1, Guan Yan
In ancient times, official swallow refers to the bird's nest dedicated to the royal family, which is generally called "official swallow", "tribute swallow" or "Bai Yan". This kind of bird's nest is of the best quality and rare in quantity, belonging to the top bird's nest. The official swallow is white in color and smooth in physique. Generally, it is cup-shaped or half-bowl-shaped, which is very beautiful. The average nest thickness of official swallows is 30-50 mm, the length is about 5-10 cm, and the width is 4-8 cm. The weight of each official swallow is about 7-12 g.. Moreover, the official swallow's hair is big, and the high-quality official swallow can reach 8-10 times.
2. Mao Yan
There are many impurities in this kind of bird's nest, and there are many swallow feathers, and the appearance is not as good as that of the official swallow.
3. Cao Yan
Cao Yan's living environment is complicated, and she mainly uses shredded grass to mix her saliva to build a nest. The nutritional value and appearance are not as good as those of Guan Yan and Mao Yan, so it is cheap and is mostly used to make instant bird's nest.
4. Bai Yan
Generally, the color of bird's nest is yellow or white, so it is difficult to have pure white. The off-white bird's nest is Bai Yan. This kind of bird's nest is not fire-resistant, so it can't be stewed for too long, otherwise it will turn into water.
5. Huang Yan
Huang Yan is generally grayish yellow or yellowish brown. This is because swallows spit out saliva with strong gel, and the bird's nest made of this saliva becomes yellowish after air oxidation. However, it should be noted that some unscrupulous merchants will dye the bird's nest with liquid medicine or make some inferior bird's nest yellow under the sun exposure, so as to pretend to be Huang Yan.
6. Blood Swallow
Blood swallow is a reddish-brown bird's nest, and it is mainly a cave swallow. There are three reasons for its color: one is that the saliva contains more minerals, which leads to the oxidation of bird's nest into red; One theory is that the color of minerals on the stone wall penetrates into the bird's nest, which leads to the discoloration of the bird's nest; The third argument is that the air in the cave is sultry, and the bird's nest containing minerals is oxidized in the sultry air and becomes gray-red or orange-red.