What Is Dry Cleaning?
Dry cleaning is a method of cleaning garments and textiles using a solvent instead of water. Despite its name, dry cleaning still uses a liquid during the cleaning process. The difference is that the cleaning liquid is a specialized solvent rather than water.
In conventional wet washing, water is combined with laundry chemicals and mechanical action to remove soil and stains. In dry cleaning, a solvent is used to dissolve and remove different types of soil, particularly oil- and grease-based stains.
The cleaning principle of dry cleaning still involves a combination of solvent, cleaning agents and mechanical action. However, dry cleaning equipment and solvent handling systems are generally more complex than conventional washing machines that use water.
Solvents Used in Dry Cleaning
One of the traditional solvents widely used in the dry cleaning industry is perchloroethylene, commonly known as Perc or PCE. It is effective in removing many types of oil- and grease-based soil.
In addition to Perc, the dry cleaning industry also uses other solvents, including hydrocarbon solvents and other specialized cleaning solutions. The choice of solvent depends on the equipment, the type of garments being processed, cleaning requirements and safety considerations.
In dry cleaning systems using Perc, the solvent is commonly recovered, filtered and processed for reuse. Solvent recovery is an important part of the equipment because it helps reduce solvent consumption and limit the release of solvent vapours.
Why Do Some Garments Need Dry Cleaning?
Not all garments and textiles are suitable for conventional wet washing. Some materials may shrink, lose their shape, fade or experience changes in quality when exposed to water and mechanical action.
Water-Sensitive Materials
Some materials and garment constructions may be affected by water. Wool, silk and certain fabrics with special structures may shrink, become distorted or lose their original characteristics if they are not cleaned using an appropriate method.
For these garments, dry cleaning may be a more suitable option depending on the manufacturer's care instructions.
Removal of Oil- and Grease-Based Stains
The solvents used in dry cleaning can effectively treat many types of oil- and grease-based stains. This is one of the important reasons why dry cleaning is used for certain garments, uniforms and textiles with specific cleaning requirements.
Helping Maintain Garment Shape
Some garments have complex structures, such as suits, jackets, lined garments or clothing with shaped components. Conventional washing may affect these structures if the garments are not processed correctly.
Dry cleaning can help reduce some of the effects of water on materials and garment construction, supporting the preservation of the garment's original shape.
The Dry Cleaning Process
The dry cleaning process may vary depending on the equipment, solvent and type of garment. However, a typical process generally includes the following steps:
1. Inspection and Sorting
Before cleaning, garments are inspected for fabric type, colour, stains and special care requirements. Items left inside pockets should also be removed before processing.
Sorting helps ensure that the appropriate cleaning programme and treatment method are selected for each type of garment.
2. Spot Treatment
Localised stains such as oil, ink, cosmetics or other difficult stains may require treatment before the garments are loaded into the machine.
This step is performed using appropriate cleaning agents and treatment methods based on the type of stain and fabric.
3. Cleaning with Solvent
The garments are loaded into the machine according to the equipment's designed capacity. Solvent and appropriate cleaning agents are introduced during the cleaning cycle.
The rotating drum provides mechanical action, allowing the solvent to contact the fabric and assist in the removal of soil and stains.
4. Extraction and Solvent Recovery
After cleaning, excess solvent is removed from the garments during the extraction process. The used solvent is then directed through the equipment's filtration and treatment system.
Depending on the system design, the solvent may be filtered to remove lint, soil and other impurities. This process helps maintain solvent quality before reuse.
5. Drying and Solvent Vapour Recovery
In modern dry cleaning systems, the drying stage not only dries the garments but also supports the recovery of solvent vapours.
Solvent vapours released during drying can be recovered through condensation or other specialized recovery systems. The recovered solvent may then be returned to the system for reuse.
Many dry-to-dry machines perform washing, extraction and drying in the same chamber. Garments enter the machine dry and are removed after the complete cleaning cycle.
6. Aeration and Garment Finishing
After drying, the garments are aerated to reduce residual solvent vapours before they are removed from the equipment.
Depending on the type of garment, post-cleaning operations may include ironing, pressing, reshaping or other finishing processes.
How Does Dry Cleaning Equipment Work?
Dry cleaning equipment may include transfer systems, where washing and drying are carried out in separate equipment, or dry-to-dry systems, where the main stages are completed within the same machine.
In a dry-to-dry system, garments enter the machine dry. The equipment performs cleaning with solvent, extraction to remove excess solvent and drying before the garments are removed.
A key feature of dry cleaning equipment is the solvent handling and recovery system. Used solvent must be filtered to remove soil and impurities. During drying, solvent vapours are recovered to reduce solvent loss and allow the solvent to be reused.
Because dry cleaning uses specialized solvents, equipment selection, operation and maintenance should follow the manufacturer's instructions and applicable chemical safety requirements.
How Is Dry Cleaning Different from Wet Washing?
The main difference between the two methods is the cleaning medium. Wet washing uses water combined with laundry chemicals, while dry cleaning uses specialized solvents.
Wet washing is suitable for many common types of textiles and can effectively remove a wide range of soil. Dry cleaning is generally selected for garments with specific care requirements, materials that are sensitive to water or stains that are more suitable for solvent-based cleaning.
The choice of cleaning method should be based on the material, garment construction, type of stain and the manufacturer's care instructions.
Important Considerations for Dry Cleaning Operations
Dry cleaning involves more than simply replacing water with a solvent. The equipment and operating process must be appropriate for the solvent being used.
Operators need to pay attention to solvent control, maintenance of filtration and recovery systems, equipment inspection and compliance with safety procedures. Solvents and waste generated during dry cleaning operations should also be managed in accordance with applicable requirements.
For professional laundry operations, the selection of suitable dry cleaning technology should consider the type of garments, operating capacity, solvent used and safety requirements throughout the process.
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