On the operation counter in the laundry shops, dealing with each stained piece of clothing is a microscopic “battle”. A mixture of solid dust, oil, and protein stains adheres to fabric fibers through static electricity, chemical bonds, and other “shackles.” The job of laundry is to rely on a detailed understanding of the characteristics of dirt and use scientific methods to break down these stains by layer so that clothes can be clean again.
Step 1: Determine the Stain Type
When you pick up a piece of stained clothing, you must first determine the stain. Color is an important basis for judgment. For example：
Light yellow to brown stains: They may be traces of oxidised animal or vegetable oils, or special stains containing tannins, such as coffee stains and tea stains, or they may be the oxidised protein stains (such as sweat stains and blood stains)
Coloured stains: Special stains, such as juice and soy sauce, often appear in different colors, such as red, purple, and brown, because of the specific chromophores.
In addition to colour, you also need to look at the form of the stain (liquid or solid particles), the feel of the adhesion (hard and brittle or sticky), and test the reaction characteristics (use a reagent to lightly touch and judge, such as using rust remover to test rust stains).
Mixed stains are common. For example, collar stains are often a combination of sebum (liquid stains), sweat (specific stains containing protein), and dust (solid stains). Oxidation can also lead to stubborn brownish-yellow stains. This step is crucial for distinguishing the primary stain type and choosing between dry cleaning and water washing based on the fabric’s characteristics, setting the treatment.
Step 2: Pretreatment
Pretreatment is more targeted according to the characteristics of different stains:
Oils (animals, plants, or minerals): Solvents break down oils directly in dry cleaning. In water cleaning, solvent-based degreasers or nonionic surfactants mix oils with water and break them down.
Protein soils (blood, milk, etc.): Enzyme solutions or oxidizing agents (oxygen bleach, hydrogen peroxide) break protein chains, with water temperature carefully controlled to prevent coagulation.
Special coloured stains (juice, soy sauce, etc.): We should employ mild oxidants to break down the molecules that make the colour. When dry cleaning, you should use oxidisers that work with solvents. When doing water cleaning, you should use products that are based on oxygen. In the two cases, you need to avoid damaging fabric.
Solid soils (mud, dust clumps): Nonionic surfactant-based agents in dry cleaning, or warm water with surfactants in water cleaning, loosen adhesion and prepare for the main wash.
Step 3: Main Wash Program
After people choose dry cleaning or water washing according to the fabric, the main wash program is carried out according to scientific logic:
Dry Cleaning: Organic solvents go into fibers. Specialized pretreatment agents form an adsorption layer on the fiber surface, solubilizing water-soluble dirt, and the drum’s mechanical force shakes off dirt. Nonionic surfactants form protective films to prevent redeposition.
Water Cleaning: The detergent thoroughly moistens the fibers and the surfactants lower the surface tension of water, which improves the repulsive force between dirt and fibers. Mechanical force helps remove the dirt. In addition, softeners eliminate the interference of hard water ions on surfactants.
Whether it is dry cleaning or water washing, key parameters must be controlled:
Ensure solvent purity and circulation speed during dry cleaning.
Control surfactant concentration (which must be higher than the critical micelle concentration) and water temperature during water washing.
Ensure that different types of dirt can be stably suspended in the medium.
Step 4: Post-Treatment
Taking clothes out of the dry cleaner or washing machine is not the end of the job.
Residual marks: Solvent residues in dry cleaning due to insufficient drying should be treated with pure solvent and air-drying. Watermarks after water washing are mainly due to dense fabric (uneven dryness and wetness) and the accumulation of free pigments can be corrected with neutralizing solutions and heat drying. You can use a damp cloth dipped in neutralizing acid water to wipe. This can help balance the pH of the fibers while dispersing the pigment. Also, use a hot air blower to dry it to prevent the mark from solidifying.
Stubborn edges: Cuffs, collars, and seams may need hand-applied stain removers for complete cleaning. (Dry cleaning: solvent-based stain removers Water cleaning: water-based stain removers)
Fabric care: Adjust the treatment method according to the characteristics of the fiber. Pay attention to moisturizing and shaping wool fabrics after dry cleaning.
Control the ironing temperature after washing to prevent fiber brittleness.
During the final inspection, laundry shop staff will focus on those areas that were stained to check whether they have been cleaned.
The Underlying Logic Of Scientific Laundry
The key to this stain removal is matching specialized technologies with dirt characteristics and washing methods: dry cleaning is good at dealing with oil stains and sensitive fabrics, while water washing has more advantages in removing water-soluble dirt. Enzymes and surfactants are essential tools in both cleaning methods. Washing clothes is not a simple “soaking and stirring,” but a precise operation based on the dirt removal technology, so that each type of stain can find a corresponding solution to break it down, finally achieving the cleanliness and renewal of clothes.
