The primary particles are very much smaller than the pores of the filter paper, but they cannot pass through, because they are held together in the form of much larger secondary aggregates.

• 陈化的作用主要是使小颗粒以及颗粒上不完整的部分不断溶解，大颗粒不断长大，在这过程中使被吸留或包夹的杂质或母液释放出来。