When tanning fur, we must first soften the raw materials, restore the fresh state of the skin, and remove unnecessary components (subcutaneous tissue, connective tissue, meat residue, muscle membrane, etc.). ) In fur processing. Comprises the following processes:

⑴ Soaking: It has a great influence on product quality. The operation method must be strictly implemented. The purpose of soaking is to restore the fresh epidermis of rawhide, remove some protein, and remove impurities such as blood stains and feces. The soaking temperature depends on the kind of hides, and is generally 15- 18C. For example, the skin below 18C softens slowly, and bacteria above 20C are easy to multiply. Soaking time: Generally, salt skin or dried salt skin can be soaked in running water for 5-6 hours. If the dried skin or salt dried skin is stored for a long time, it should be softened by physical or chemical methods during soaking. The soaking time can be 20-24 hours. It is required that the skin flap should not be wet, soaked, soaked and even. Pay special attention to the temperature and soaking time when soaking. Based on the principle of rawhide swelling in alkaline water, the soaking time of rawhide can be reduced and bacterial reproduction can be inhibited. Sodium sulfide, sodium hydroxide, ammonium hydroxide, sodium sulfite, etc. Often added to the soaking solution. The dosage of sodium hydroxide is 0.2-0.5g/L, and the dosage of sodium sulfide is 0.5-1g/L. ..

(2) Internal shearing: soak in water to soften the fur. Spread it upside down on a semi-circular log and scrape off fat, leftover meat, etc. Attach to the meat surface with an arcuate knife. In order not to hurt the hair roots, you can spread a thick cloth on the log first when scraping. Crushing is closely related to the subsequent degreasing. If there is too much residual fat, it is not conducive to degreasing. The function of scraping the inside of the bow knife is to make the residual fat in the skin rise to the surface of the skin by extrusion, which is beneficial to degreasing.

(3) degreasing and washing: the quality of finished fur depends on whether degreasing is complete or not. In the degreasing process, the fat should be removed without damaging the fur. Saponification method is mild, and its principle is to use the properties of soap generated by alkali and grease to remove grease from the coating. If the alkali solution is too concentrated or strong alkali is used, the cutin of fur can be destroyed, and the hair will lose its luster and become brittle. Generally, soda ash is used, which is weak in alkalinity, and can remove grease without causing damage to wool. But the concentration of lye should be controlled. If the concentration is too low, the purpose of degreasing will not be achieved. The product hardens and has the original smell of animals, which will also affect the next tanning process and make the skin stiff and not durable.

Degreasing method:

A. firstly, prepare degreasing solution, 3 parts of soap, 1 part of sodium carbonate and 10 part of water. Slice the soap first, put it in water to boil and dissolve, then add sodium carbonate, and let it cool after dissolution. Add warm water (38-40C) which is 4-5 times the weight of wet skin into the container, add 5- 10% degreasing solution (rabbit skin and sheepskin 5%, dog skin 10%), then put the shaved fur, fully stir it, and change it again after 5- 10 minutes.

B Degreasing liquid can also be prepared with washing powder (3g/L) and soda ash (0.5g/L), so that the weight of the treated liquid and wet skin is 10- 12 times, heated to 38C, degreased and stirred for 40 minutes, and enzyme washing powder is better in the market. 1 liter of water is replaced with 3g washing powder, 0.5g. Peel and dry.

2. Tanning process (only alum tanning method, its source is simple and convenient).

(1) Prepare tanning liquor, 4-5 parts of alum, 3-5 parts of salt and 0/00 part of water. First, alum is dissolved in warm water, and then the remaining water and salt are added to make them mix evenly. Principle: After alum is dissolved in water, it generates free sulfuric acid, which can make protein fiber in skin absorb water and expand. The purpose of adding salt is to inhibit expansion, but the amount of salt added depends on temperature. You can add less salt when the temperature is low, and more salt when the temperature is high. Generally, 0.7-2 parts of salt can be added according to 1 part of alum.

(2) Tanning method: the ratio of material to liquid is 4-5: 1 (when the wet skin weight is 1, the tanning liquid is 4-5). Put it into a container, so that the fur is fully soaked in the feed liquid. In order to make the feed liquid evenly penetrate into the cortex, it should be fully stirred (preferably with a roller), stirred once a day after overnight for about 30 minutes each time, and soaked for 7- 10 days to finish tanning.

(3) Inspection method: If the tanning is good, take out the soaked leather, with the leather board facing outward and the plush folded inward, and press the water out at the corners. If the folded part is white and unclear, like tissue paper, it proves that tanning is over. The low water temperature during tanning not only prolongs the tanning time, but also hardens the cortex. It is best to keep the temperature at about 30℃. After tanning, don't wash the inner surface with water, just wash the rough surface with water. Alum tanned fur is white and soft, but it lacks water resistance and heat resistance.

3. Finishing process.

(1) fatliquoring.

During the processing, the original fat in the skin has been removed. In order to form a protective layer of fat film around skin fibers and improve the softness, elasticity and strength of skin, it is necessary to add fat. Now a simple fatliquoring formula is given for reference: castor oil 10, soap 10 and water 100. Boil the soap slices and dissolve them in water, then slowly add castor oil for emulsification and fatliquoring. Combination of inner surface and inner surface >: Let it dry overnight.

(2) resurgence.

The greased and dried skin is very hard. In order to scrape it soft, it is necessary to spray water on the inner surface properly. This process is called "moisture regain" The inner surface can be brushed with a brush or sprayed with a sprayer. For the fur tanned with alum, it is best to coat it with alum tanning solution because of its lack of water resistance. After painting, fold the inner surface and the inner surface, wrap them with tarpaulin or plastic cloth, and press a stone.

(3) scraping soft.

Spread the wet fur on a semi-circular wood, with the fur face down, and gently scrape the inner face with a blunt knife to make the fur fiber longer, the area larger and the leather board softer.

(4) shaping and decorating.

In order to make the scraped leather board smooth, it needs to be reshaped. Nail the wool face down on the board, dry it in the shade to avoid sun exposure, and smooth the surface with pumice or sandpaper after it is fully dried in the shade, and then remove the nail board for trimming. Then comb it with a comb and sew it when it is broken. It's all done.

Matters needing attention in this method of nitrocellulose,

(1) This is a fur curing method, and leather has little influence, for example; Suede, in the process of treatment, will shed its hair and become hairless. After nitrification, the effect is not significant. Because of its salt content, it is impossible to make a scabbard. It is a rusty knife. But leather nitrates well because it contains less oil.

(2) If you make decorative leather, you must peel it back, that is, cut a knife from the midline of the hind foot and peel it into a tube skin as a whole, so as to look good.