FACTS ABOUT REDEPOSITION

When insoluble particles are released from a fabric while being cleaned, the soil particles will become suspended in the solvent and picked up by the filter.  However, before passing through the filter, loose soil particles may be attracted to a fabric in the wheel, which results in an overall gray or dull appearance. 

Sometimes the redepostion will be limited in area to a streak or blotch.  Not every garment in a load may be affected.  Often, only one garment is affected.  Resin finishes, which give the fabric easy care features, attract loose soil particles.  Polyester, nylons, acrylics as well as woolens when abraded (from the rotation of the drum) during dry cleaning, become electrically charged and attract loose soil particles.  Once attracted to the resin finish or electrically charged fibers, these particles cannot be easily released.

SUGGESTIONS TO AVOID REDEPOSITION

The two basic objectives in avoiding redeposition are to remove the soil from the garment and then to remove soil from the solvent as quickly as possible.  Even where solvent purity is properly maintained, redeposition may occur under certain predictable circumstances, which can usually be avoided.

(1)   Improve the flow of solvent from the wheel, through the filter, and back to the wheel. The complete changeover of solvent in the machine should require no more than 1 minute.  The possibility of redeposition increases as the flow of solvent decreases. The reason for a slow solvent flow may be the result of clogged disc filters or cartridges, a faulty or clogged solvent pump, a clogged button trap or pump screen, or clogged inlet or outlet lines.  High or low filter pressure could be an indication of a filter problem.

(2)   Pure solvent. If the machine is fitted with a still, distillation is required to remove solvent soluble impurities.  The filter removes only the insoluble soil such as soot, carbon and dust, and lint.  For each 100 pounds of garments, it is desirable to distill at least 10 gallons of solvent. Spin disk filters require more distillation to maintain the purity of the solvents (16 gal per 100lbs). If the machine is not fitted with a still, large format cartridge filters that contain either clay or a larger carbon core are sometimes used in machines that do not use perchloroethylene. These filters will remove solvent-soluble as well as insoluble impurities from the solvent. These types of filters must be changed in accordance with the manufacturer’s recommendations.

(3)   Improper detergent injection or detergent concentration charge.  Most detergents hold insoluble soil in suspension.  Detergents are also helpful in minimizing the undesirable effect of moisture on many fabrics.  The detergent manufacture suggestion for concentration and addition should be maintained. 

(4)   Proper load classification.  Dark color garments usually release more dye and can be assumed to carry more soil.  When light and dark colored garments are dry cleaned in the same load, redeposition is more likely.

(5)   High moisture retentive fabric.  Many fabrics such as cotton, wool and rayon can retain a high percentage of moisture and will attract more loose soil when wet or damp.  If these garments are not allowed to dry after wetside spotting, they will attract soil when loaded into the dry cleaning machine.

(6)  Overloading the wheel prevents circulation of the solvent especially to the center of the load.  The insoluble particles become trapped and are more easily redeposited onto the fabric instead of being pumped through the filter.

(7)   Excessive solvent temperatures. Solvent temperatures should be maintained between 75-80 degrees F.  Hot solvent releases moisture and dyes that can contribute to redeposition

(8)   Excessive dyes and impurities.  The solvent color should be lighter that the color of a light beer.  Increased distillation and (or) more frequent carbon cartridge changes will aid in solvent maintenance.

(9)   A malfunctioning still that releases impurities along with the distillate.

Determining redeposition on garments

a.       Applying oily type paint remover or a P.O.G. to the affected area(s)

b.      Tamp vigorously.

c.       Apply a few drops of ammonia

d.      Tamp vigorously.  If the area becomes lighter, the problem is redeposition.

 

Correction Procedure

The procedure for the removal of redeposition is time consuming and is frequently unsuccessful.  Localized areas should be pre-spotted with oily type paint remover or a P.O.G., then tamped and rerun.  Sometimes rust remover is effective on an affected area that attracted metallic impurities.  For large areas use the following:

(1)   Soak the garment in a high detergent concentration in the basket.

(2)   Batch the garment for 10 minutes, then run on filter for 8 minutes.

(3)   If the previous method was unsuccessful, try soaking the garment overnight, using sodium perborate or sodium percarbonate (2 ounces/gallon of water) with a mild synthetic laundry detergent. Rinse thoroughly, then neutralize the bleach by souring with a mild acid. Rinse again.    

           Correcting soil redeposition is time consuming and the results are unpredictable.  It is far better to avoid redeposition with the following:

(1)   A properly functioning still and filter

(2)   Proper load classification

(3)   The addition of clear (“make-up”) solvent

(4)   Proper solvent temperatures

SOLVENT PERFORMANCE TEST

Take a white cotton swatch or handkerchief and cut it in half.  Clean one half and use the un-cleaned half for a control.  Compare the color both pieces after cleaning.