Raw tung oil is a kind of A-type tung oil. Under the action of ultraviolet rays, it will quickly transform into P-type tung oil. Therefore, if raw tung oil is used to directly paint the surface of the object, the paint film will be unstable and easily become opaque and milky white, which will cause adhesion. Focus on lowering. For this reason, we must boil raw tung oil into mature tung oil. The operation process is as follows:
(l) Pour the raw tung oil into the cast iron pot first, and then heat it with firewood. The heating rate is basically maintained at 1o°C per minute, and when the temperature rises to 15o°C, keep warm for 3 minutes. If the oil temperature rises too fast, the water will not evaporate in time, and a large amount of oil foam will overflow out of the pot and cause an accident. Therefore, use a small fire to boil the oil. When a large amount of foam is no longer produced in the oil, it means that the water in the oil is basically boiled dry. At this time, firewood should be added to heat up. When the oil in the pot boils and foams, and when the oil fume increases, pour the oil while pouring to exhaust the oil fume as much as possible. When the oil boils until it smokes, the color of the oil changes from yellow to dark, and the oil temperature can reach about 23o℃ at this time. Take an "oil sample" immediately to see if it has reached the viscosity required by the base oil. If there are 3~ When it is 4 cm long, it means that the tung oil has been basically boiled. At this time, the oil should be quickly poured into a cold iron pan and cooled rapidly. The time to boil the oil is generally controlled within 30 minutes. The tenderness of base oil is determined by the length of holding time after 23o ℃. Long holding time is called old oil; short holding time is called tender oil.
(2) Cook the varnish at a maximum temperature of 25°C. The degree of cooking can be judged from the oil surface: after the water vapor in the oil keeps escaping, the oil bubbles turn from white to yellow, and the sound of oil turns from blunt to brittle. At this time, it shows that the oil is mature, and it should be annealed immediately, and the driers Tuzi and Miduo can be added. Stir well, and continue to "breathe smoke" until the smoke in the pot is exhausted and the oil is cold, and you can use the oil paper and use it.
When boiling varnish, the amount of drier varies with the seasons. The ratio of tung oil to Mituseng and Tuzi is as follows:
Raw tung oil 1oo Mytha monk 1.25
According to the season, summer 1.5, spring and autumn 2, winter 3
The varnish is used for surface varnish. When boiling the oil, add 1% rosin powder at the same time as the Mitha monk, which can increase the brightness of the finish paint film.
