The main systems for keeping it free from colour and particulates are filtration and distillation.

New machines may offer the option of a colour filter cartridge, which uses carbon.

Some cartridge filters also use absorbent clays to control moisture and fatty acids.

Cartridge filters need to be replaced on a regular basis as they will eventually become saturated.

The length of time this will take depends on the type and volume of work.

Cleaners that handle a high proportion of household and items prone to colour loss will need to replace these cartridges more frequently.

Filtration is mainly used to remove particulates and to clarify the solvent efficiently. The filters must be operated within the correct filter pressure range as specified by the machine manufacturer/supplier.

It is important that the maximum pressure is not exceeded, recommended maximums for modern disc filters vary but are not generally above 2barM (28psi). The supplier’s advice on filter maintenance must also be followed precisely.

To keep soluble impurities at low and acceptable level, the ratio of solvent distilled to the weight of work cleaned must be sufficient. Research by the former FCRA shows that, for perc, this should be a minimum of of 2.5litres solvent/kg work.

Keeping to this ratio will ensure solvent stays in good condition.