Ejiao is as yellow as amber and as light as dark. Real people have no skin odor, and they are neither wet nor soft in summer. Fire test: put a few samples into the crucible to burn, which will burst at first, then expand and melt, giving off white smoke with strong fragrance of sesame oil. After ashing, the residue is dark black, loose, flaky or massive, and does not stick to the crucible; Test water: Boil and dissolve, the solution is light brown-red, turbid, with white material precipitation and oil droplets on the liquid surface. Dissolve the glue in water, and the liquid is clear without turbidity; Clap your hands: Clap the table with your hands. If the fragment is brown, translucent and free of foreign objects, it is true. If it is soft but not broken, it is suspected to be counterfeit. The first fake of Ejiao is Niu Pijiao, which is hard and not easy to break. There is a strong smell when burning, and there is no oil drop on the surface of the test water. The second is miscellaneous leather glue, which smells like soybean oil when burned, and the test water is dark gray-brown red with a small amount of oil spots on the liquid surface; Third, bone glue, the surface is opaque, dull, with small holes caused by bubbles, irregular wrinkles on the side, hard and not easy to break, and slightly smelly; The fourth kind is gelatin, which is smooth and bright, crisp, slightly gassy or smells like ink. After fire test, it becomes white flake powder and does not stick. In addition, the donkey-hide gelatin solution does not agglutinate after standing for 4 hours, and the fake medicine solution condenses into paste. In addition, the appearance of turtle glue and deer glue is similar to that of donkey-hide gelatin, which should also be identified: turtle glue, with a brown surface and a slightly green surface, has a yellow "oily head" on it, which is as clean as amber and is not easy to ignite; Deer glue, dark brown surface, translucent to light yellow, single-sided yellow-white porous thin layer, crisp and crisp, reddish brown cross section, glass luster.