Unless you are bald, you will probably get hair and dandruff in your emulsion along with lint from your clothes. In addition, sometimes there are gelatin 'slugs' that do not melt properly and are left in the melted emuslion.
But, you are right. Sometimes aggregates form that must be filtered out. These are virtually never seen in ammonia digest emulsions, but are often present in other emulsions. They are often prevalent in home made emulsions due to the quality of gelatin sometimes sold, and sometimes just due to the formulas used.
Washing does not remove particulates.
PE | 
filtering 
Linear Mode
