Streaks And Swales

Following on from the bulletin about low levels of solvent in the machine, one of the consequences can be streaks and swales on certain garments.

Streaks and swales in dry cleaning
by Howard Duffy, DIA Technical Officer

Following on from the bulletin about low levels of solvent in the machine, one of the consequences can be streaks and swales on certain garments.

To prevent streaks, you must understand what causes them in the first place. Poor drying and non-volatile residue (soil and dirt) are the underlying cause of streaking in drycleaning.

Non-volatile residue refers to the substances left behind when solvent is evaporated. These substances can include oils and greases, detergents, sizing’s, and nearly all soils removed from the garments. Don’t be mistaken and assume just because your solvent is clear it contains no non-volatile residue.

Both overloading the machine and underloading causes this problem. Underloading allows garments to stick to the surface of the drum, this prevents the falling of the garment during tumbling action that allows the garment to open and be available to the drying air flow.

Overcrowding in the wheel causes folds in the garments as they lay bunched together. In order for the solvent in the centre of the garment to evaporate during drying, it must work its way to the surface. As the solvent works its way to the surface, it pulls any non-volatile residue along with it through the folds of garment. When the solvent reaches the surface, it evaporates leaving the residue on the garments in the form of streaks and swales.

Improper Sorting of Loads

Sorting each load correctly will greatly reduce the chances of streaks and swales. Not all items in the load dry at the same rate. If you dryclean a silk blouse with a wool coat, the lighter weight silk garment will obviously dry before the larger, heavier coat does. As the drying cycle continues, the wool coat, which is still damp with solvent, tumbles against the silk blouse. Every time the damp coat touches the dry blouse it leaves a wet mark. When the wet area dries, streaks will remain if high levels of non-volatile residue are present in the solvent.

Extraction Efficiency

The amount of extraction the load is given can play a part in the formation of streaks. The purpose of extraction is to remove solvent from the items being cleaned. When the extraction cycle is cut short, more solvent is left in the garments than if the extraction cycle was completed. If the solvent is loaded with non-volatile residue, it stands to reason that the more solvent is left in the load, the more non-volatile reside will be retained in the garments when they go into the drying cycle, increasing the chances of streaks and swales.

Preventing Streaks and Swales

In summary, streaks and swales can be prevented by following a few simple guidelines:

  1. Keep your solvent clean.
  2. Never overload the wheel.
  3. Never underload the wheel.
  4. Do not clean heavyweight garments with lightweight garments.
  5. Allow the extraction cycle to be completed before drying begins.
  6. Use discretion when netting garments.


To restore items affected by streaks and swales simply reclean or rinse the items in fresh, clean solvent while following the guidelines mentioned above.