A Brief Discussion on Laundry Linens
Release Time:
2011-09-01 13:35
Source:
www.chinalaundry.cn
Wang Fenggang
The laundering of linens in guesthouses and hotels is a task involving large quantities and high quality. It is not only necessary to thoroughly remove dirt from the linens but also to focus on extending their service life. To achieve ideal results, scientific washing methods and reasonable washing procedures must be adopted. Through years of exploration, I have gained a deep understanding of various factors in the laundering process, such as washing time for each step, types and amounts of detergents, water level and temperature, and pH value. I now share these insights with colleagues for further discussion.
1. Rinsing
Rinsing is the first step in washing. Its purposes are: first, to moisten the linens so that the fabric fibers expand, facilitating the removal of dirt and aiding in cleaning; second, to use water and mechanical action to remove as much water-soluble dirt as possible from the linens, thereby reducing detergent consumption in subsequent steps. This process requires no addition of chemicals; proper rinsing alone can achieve the goal. Therefore, it is crucial for subsequent steps and reducing washing costs. Currently, many laundries do not have a rinsing step or consider rinsing only as moistening the linens. They drain water as soon as the linens are just wet, but at this point, the linens have not been fully soaked and rinsing cannot effectively remove water-soluble and surface-adsorbed dirt. Thus, skipping rinsing or only moistening the linens is not advisable.
The water level for rinsing should be medium. Many rinsing processes use a high water level. Practice has shown that although a high water level provides more water, it weakens the mechanical action generated by the washing machine drum due to excessive water, reducing the impact force of the water and affecting rinsing effectiveness. Choosing a medium water level can increase the water's impact force and better utilize the drum's mechanical action. Therefore, rinsing is best done at a medium water level. The rinsing time should be 2-3 minutes, with water temperature set between 30°C and 40°C. Too low a temperature does not sufficiently expand fabric fibers, hindering dirt removal. Too high a temperature can fix some dirt, such as protein-based stains, which denature and coagulate under high heat, making removal difficult. Rinsing should be done 1-2 times.
2. Pre-wash
The purpose of pre-washing is to loosen dirt on the linens to prepare and provide favorable conditions for the core stain removal stage. Due to water tension and dirt removal principles, water alone cannot wet most dirt. For heavily soiled linens, special wetting agents or detergents with high wetting agent content should be added during this step to wet certain stains and ensure effective pre-washing. Currently, few laundries correctly use the pre-wash program; some do not have a pre-wash step, some combine it with rinsing, thinking rinsing is pre-washing; others do not add pre-wash agents during pre-washing. These practices negatively affect washing results. The water level, temperature, and time for pre-washing should be the same as rinsing, and pre-washing is generally done once.
3. Main wash
The main wash is the core stage of linen laundering and the key step determining washing effectiveness. In this process, water acts as a medium combined with the chemical action of detergents, appropriate water temperature, time, and other factors working closely and reasonably to create a relatively ideal stain removal environment. This detaches dirt adsorbed on the linens, achieving the goal of removing dirt and cleaning the linens. This is a complex reaction process. The design of the main wash program and the choice of detergents are crucial. During the main wash, detergents should be selected based on the type of dirt on the linens, washing temperature should match the detergent, and washing time should be designed according to the degree of contamination. The water level during the main wash is generally low to increase detergent concentration and effectiveness. Washing temperature is 62°C-75°C; too high a temperature causes surfactants on the linens to form gels, reducing detergent cleaning ability. For pure cotton fabrics, the temperature can be slightly higher. The pH value should be controlled between 10 and 11.5. Washing time is generally 8-10 minutes. Too short a time prevents the necessary actions and reactions from occurring, reducing stain removal; too long increases fabric wear and energy consumption.
4. Bleaching
The purpose of bleaching is to eliminate residual oxidizable or reducible pigments and dirt on the linens, purifying the fabric surface. It helps maintain good whiteness for white linens and enhances color for colored linens. The effectiveness of bleaching depends closely on the quality of the bleach, pH, temperature, and time. Previously, control was mostly based on experience; now it can be measured and determined by bleach concentration and maintenance time. In practice, I insist that bleach be added only when the washing water reaches the set temperature to ensure rapid and even dissolution, avoiding uneven distribution that causes local damage or discoloration. The water level is low to maintain high bleach concentration for full effect. Water temperature is controlled between 65°C and 75°C (note: chlorine-containing bleach), pH generally below 11, and time usually 6-8 minutes.
5. Rinsing
The purpose of rinsing is, under high water level conditions, to use mechanical action to diffuse residual detergents and dirt-containing wash water from previous washing steps into the water and then drain them away. The rinsing stage is an important step to ensure the quality of washed linens. Water level should be high, water temperature between 30°C and 40°C, and rinsing should be done 2-3 times.
6. Post-treatment
The purpose of post-treatment is to physically and chemically treat the cleaned linens according to different uses to meet user requirements. For example, "neutralization" offsets residual alkali in washed linens and possible bicarbonate, rust, calcium soap, etc., in water to adjust the linen's pH closer to human skin pH, increasing comfort. Post-treatment processes include softening, sizing, etc. Water temperature is generally around 30°C, and pH should be controlled between 6.5 and 6.5.
7. Dehydration
Dehydration is the final step in linen washing, using the high-speed rotation of the washing equipment to reduce the moisture content of the washed linen to the minimum. Time: generally 8-10 minutes is appropriate.
In summary, a standardized linen washing procedure and method is an organic combination and dialectical unity of chemical action, physical action, time, temperature, and water, ultimately achieving a balance. Only with a scientific and pragmatic attitude, continuously exploring and summarizing in practice, can one continuously discover, improve, and progress.
(Author's affiliation: Trainee at the Laundry and Dyeing Committee Training Center)
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