Oil flow observation method. Take two measuring cups, and one contains dimethyl silicone oil 1000cst to be inspected, and the other is empty on the table. Lift the measuring cup full of oil 30-40 cm away from the table top and tilt it to let the oil flow into the empty cup slowly. Observe the flow situation. The one with good quality should be long, thin, uniform and continuous. If the oil flow is fast or slow, there is a large flow sometimes, and it is said that it has deteriorated.
Illumination method. On a sunny day, use a screwdriver to lift up dimethyl silicone oil 1000cst at a 45 degree angle to the horizontal. Compare with the sunlight and observe the oil drop. Under the light, it is good to see that there is no debris in the oil. It can continue to work. If there are too many debris, it should be replaced.
Hand twisting. Twist dimethyl silicone oil 1000cst between thumb and index finger and grind repeatedly. The hand feels of the one with better quality should have lubricity, less wear debris and no friction. If there is a greater sense of friction such as sand particles between fingers, it indicates that there are many impurities in the oil, which can not be reused and should be replaced.
Oil drop trace method. Take a clean white filter paper and drop a few drops of oil onto the filter paper. After the leakage of dimethyl silicone oil 1000cst, there is a sense of astringency when touching it with hand if there is black powder on the surface, it means that there are many impurities in the oil. If it is of good quality, there should be no powder. When you touch it with hand, it should be dry and smooth with yellow trace.