1. Fresh or dried hides. 2. Drugs: industrial formaldehyde (formalin), sulfuric acid, salt, cooking essence, mirabilite (sodium sulfate), sodium carbonate (white alkali), washing powder, penetrating agent JFC, soft white oil or synthetic fatliquor, formic acid, ammonium sulfate and sodium thiosulfate. 3. Appliances: thermometer, acid-base test paper, scraper, semicircle wood, crock, glass measuring cylinder, measuring cup, beaker, coarse scale, etc. Methods Raw hides were mixed and weighed according to step 1: Raw hides were mixed according to thickness, area, freshness or dryness of raw hides, drying degree and storage time. And hides with similar properties should be combined into a production batch as far as possible, and it is appropriate to manually operate 20-30 batches, and the weight of hides should be used as the basis of water consumption. 2. Soaking: The purpose is to make the moisture in the leather board close to the state of fresh leather and improve its softness. The amount of water added is 20 times of dry weight or 10 times of fresh skin, and the water temperature at room temperature should not be lower than 20 degrees. Add 3 ml of meal detergent and 0.5 ml of JFC to each kilogram of water. The soaking time is 24-36 hours. During the soaking process, the fur should be turned intermittently to prevent the leather board from coming out of the water. 3. Degreasing: The purpose is to remove dirt, blood and grease from fur. The water consumption is the same as above, the water temperature is 35-40 degrees, and a proper amount of detergent or washing powder is soaked in water 1-2 hours. 4. Re-soaking: The purpose is to make the skin board bright again, and the skin fibers are loose, so it is easy to uncover the inside and remove the meat. The amount of water added is the same as above, and 1 ml concentrated sulfuric acid and 1 g sodium thiosulfate are added to each kilogram of water. The re-foaming time is 2-5 hours, and the skin is swollen, bright and soft. During the re-foaming, it should be stirred and turned frequently. 5. Peel and remove the meat: after re-soaking, neutralize with sodium carbonate solution, adjust the PH value to about 7.5, and keep it for more than 2 hours, then peel and remove the meat. The method is to uncover from the tail to the head, with a blunt knife or shovel, or by hand, but to prevent the leather board from being uncovered. 6. Acid leaching: The purpose is to soften and expand the fibrous tissue of hides and prepare for tanning process. The amount of water added is 15-20 times of tare weight, and the water temperature is about 35 degrees. Add 50g of salt, 50g of mirabilite, 3ml of concentrated sulfuric acid, 1 ml of formic acid and 0.5ml of JFC to each kilogram of water. The curing time is about 24 hours, and the skin can be extended appropriately and turned frequently. The inspection of curing effect is to fold the skin in half, with the skin facing outwards, and squeeze it by hand at the folding place. If a white indentation is formed and the skin is soft, you can pick it up and squeeze it out, and then put it into the tanning liquid without dripping water. 7. Tanning: The purpose is to make leather fibers loose and stable, and to make the combination of hair and dermis stronger. The amount of water added to tanning liquor is 15-20 times of the tare weight, and 8- 10 ml of formaldehyde, 40 g of salt and 40 g of mirabilite are added to each kilogram of water. It is best to keep the water temperature at 35-37 degrees. After the pickled skins are stirred for half an hour, the PH value of tanning liquor is slowly adjusted to 8-8.5 with sodium carbonate for 3-4 times. Tanning time shall not be less than 24 hours.