The ideal solution for any cleaner is the freshly prepared working solution, just before immersion of any parts. After the initial dunk of parts, the solution becomes soiled. As production use proceeds, the bath loads up with contaminants typically consisting of oils, grease, and fine particles. In this whole process, it is important to determine just how soiled the cleaner becomes before it starts working against the user. Several quick tests can be employed to determine this and these include specific gravity, performance test and oil displacement. The cleaner can be filtered using a cartridge filter, oil absorbing filter, bag and indexing fabric filters, and ultrafiltration.