Refining cooked tung oil (base oil and varnish) needs to be based on the composition of tung oil, the conditions at that time, and seasonal changes. Under the guidance of experienced masters, do it yourself and constantly sum up experience to achieve better results.
When refining tung oil, you need to pay attention to the following points:
(l) The amount of raw tung oil added should not exceed 3/5 of the capacity of the oil pot, so as not to cause the oil foam to rise and overflow the pot, causing a fire.
(2) During refining, the maximum temperature of base oil and varnish should be controlled (generally controlled at 230~240°C for base oil, and about 230°C for varnish), and "oil samples" should be taken continuously. After reaching the required viscosity, the pot should be removed immediately and the heating should be stopped. The counting time should generally not be too long, about 30 to 40 minutes. Over time, the oil color will become darker and blacker.
(3) If there is too much oil foam or it is close to swelling, immediately add a little silicone oil or tributyl phosphate and other defoamers to avoid swelling.
(4) Tuzi and Mituseng need to be fried in advance, do not use wet Tuzi and Mituseng. If the soil is a big wish grain, it should be crushed. Amitabha should be crushed into powder before use.
(5) The quality of cooked tung oil smelted at high temperature and rapid fire is better, but due to the high temperature of the oil, it is difficult to cool for a while, and it is easy to cause gelation and scrap. Therefore, it is necessary to prepare cold oil before refining, and immediately add quenching oil when there is a sign of a change in tone, and use an electric fan to speed up the cooling process. A small amount of rosin or rapeseed oil can also be added to tung oil to delay the gelation time of tung oil.
(6) When boiling tung oil, two people should operate it, and canvas gloves and canvas foot covers (or leather boots) should be worn to prevent burns. When cooking oil, do not allow the flame to reach the surface of the pot. Stir slowly and steadily, and don't stir the oil out of the pot.
(7) The factory where tung oil is boiled is recommended to be in the open air or in an open and safe place, and be equipped with foam fire extinguishers and yellow sand to prevent accidents.
(8) After the refined tung oil is cooled, cover the oil surface with kraft paper (cut the kraft paper into the shape of oil surface, moisten one side with water, and keep the other side close to the pumped surface) to prevent the tung oil from contacting the air and forming a skin. cause waste.
