|
The Laundry Process
|
|
SOIL SORTING –
Soil classification is the process whereby incoming garments are sorted based upon specific laundering needs. This is the first step in preparing garments for specific laundering processes that are set up for different requirements. Note that even though this step is known generally as soil classification or soil sorting, not all classifications are related to soil. The most common classifications are
|
|
LOADING WASHERS Rated capacities of washers normally indicate weight, in pounds or kgs, of the soiled cotton textiles the washer manufacturer recommends, for the best results. The industry accepted standard for capacity is 5.25 pounds per cubic foot plus a factor for soil. Both polyester/cotton blends and all polyester garments weigh less per volume than cotton therefore, the total weight for a full load of these products is less than the rated capacity for an all cotton load. |
|
|
The thermoplastic character of polyester, that property which, when properly handled allows durable press fabric to remain smooth, also must be considered. The fabric must be given room to flex as the cool down takes place. Lack of movement in the fabric as the polyester fibres cool to their fixed shape can result in hard to remove wrinkles and creases (shocked).
For best results, open pocket washers are loaded at 65% of their rated capacity, split pocket washers at 60% and Y pocket machines at 50% weighed equally to each wash pocket. The introduction of washers with variable speed and high-speed wash, offers the opportunity to increase load size above these general recommendations. The increased speed sticks more of the textiles to the basket, improving lift and drop, and reducing the tumbling action that causes abrasion and wrinkling in overloaded conditions. |
|
THE WASH FORMULA No hard and fast rule exists for determining the number or composition of operations required in an industrial wash formula. AUS works closely with the chemical supply companies to ensure we use the most efficient chemical formulas for each textile type we use. The exact formula will vary according to the degree and type of soil. However, proper sorting and weighing of wash loads will help ensure the effectiveness of the four conditions of cleaning:
A regular review of equipment, soil condition, load size and analysis of water are used to set up and maintain proper formulas to ensure the cleanliness and optimum service life of the garments. Water levels that are low due to leaks will not suspend oils properly, will affect the chemical concentration, and might damage garments with excessive mechanical action. Too high a water level will reduce chemical concentrations and mechanical action, and reduce cleaning. Automatic controls are monitored to make certain that water and supplies are added at the right time, and that no operations are skipped. Load size is important as overloading will not allow sufficient mechanical action or chemical dispersion and may leave the load soiled and wrinkled resulting in high levels of rewash. Under loading wastes water and energy. If not adjusted, the resulting chemical concentration and increased mechanical action can be detrimental to the fabric. |
|
STEPS IN WASHING
A flush is often used as the first step in a wash formula to remove loose soil or potentially stain-causing matter (such as blood) or hazardous chemicals from the load. Early removal of soil, may also reduce the volume of cleaning supplies needed later in the process. The flush is usually cold water, but up to 50 deg C may be used as a temperature-conditioning step for hot break operation. The highest concentration of detergent supplies is added in the break cycle. This step removes the bulk of the soil from the fabric. Proper chemical concentrations are important to keep soil suspended until the machine drains. Average wash temperatures range from 60 deg C to 70 deg C with higher temperatures of 85 to 90 deg C used to soften and loosen some heavy soils. Highest water temperatures are used in the break along with low water levels to allow maximum mechanical action and maximum chemical concentration to do an effective job of cleaning garments. Detergent systems vary from being low alkaline (max pH 10.5) to moderately alkaline (max pH 11.5). As alkalinity and temperatures are increased above pH 10.5) and 65 deg C respectively, the potential exists for alkaline hydrolysis of polyester and subsequent loss of strength. This point is a major consideration when selecting a detergent system. Following the break there may be a carry-over or suds bath – so named because about half or the water and chemicals from the break are carried over into this cycle after draining. Dumping water from the break reduces the level of soil in the machine. This step functions to keep soil loosened from the fabric in suspension. A second suds step is sometimes used for some classifications like light colours or heavily soiled garments. Additional wash chemicals can be added in this step to address difficult soils. After soil is removed, a bleach cycle may be used on white garments to remove stains, to whiten garments, and to make them hygienically clean. Soil, if not removed, will consume bleach and make it less effective. Control of temperature, Ph, bleach concentration, and the time of exposure are important to preserving life of the garment, particularly if chlorine bleach is used. Use of anti-chlor after this cycle neutralises residual chlorine and eliminates any after effects. The purpose of the rinse cycle is to remove any chemicals or soil left after the suds bath. High water levels give maximum dilution of chemicals and flushing actions for soils. As polyester softens when heated, it must be cooled down gradually in order to prevent wrinkling that is difficult to remove later. In order to prevent thermal shock wrinkles, the reduction in temperature of subsequent rinse baths should be in small incremental steps. The last rinse should take the load down to less than 40 deg C. Cycles need to be long enough for water to penetrate the load. A sour bath is sometimes used to bring the load to chemical equilibrium by neutralising any remaining laundry chemicals. Fabric softeners also may be used in this step when laundering cottons. It is important to achieve a proper chemical balance in this step with a finished Ph of 5.5 to 6.5 to minimise problems of fabric yellowing, odour problems, and/or skin irritation issues. |
|
EXTRACTION
Once the load has been laundered properly, the stage is set for removal of excess water. This is a process known as extraction, and its operation will depend on the subsequent operations planned for the garments. For wet to dry tunnel operations, extraction is sometimes bypassed completely. Remember that poly/cotton can be made to form wrinkles when the fabric is warm and under pressure. Poly/cotton or all polyester garments need to be cooled to 40 deg C or less before subjecting them to the forces of extraction. It is helpful that polyester does not absorb moisture, and therefore requires less extraction than cotton. Centrifugal extraction should be done at low speed, and should continue for only as long as there is a steady flow of water from the drain. |
|
TUMBLE DRYING/CONDITIONING
As you recall in loading the washer, different capacities were used for all cotton garments versus those for polyester/cotton blends and all polyester garments. Since drying has many of the same conditions (such as wheel capacity, heating, cooling and tumbling action), a simple rule applies. For cottons, load dryers at the machine manufacturers rated capacity. Load at 2/3 capacity for blends and all polyester garments if they are to be pressed. For tunnel finishing better quality results with loads at 50% rated capacity. For best results, do not dry the garments completely. |
|
|
The cooling down of garments containing polyester is as important part of the drying cycle as it is in laundering. The cooling must take place while the wheel continues turning, giving action to the fabric while the polyester is still warm and soft. At 40 deg C, the polyester will have returned to its rigid state and the wheel can be stopped.
Overloaded baskets can press new wrinkles into polyester containing garments, particularly if allowed to remain in the baskets overnight. Hang the garments as soon as possible. With good control of all operations, garments hung immediately upon removal from the dryer will have remarkably smooth fabric surfaces. |
TUNNEL FINISHING Tunnel finishing serves two purposes in the modern laundry. It can replace the pressing that is usually required on all cotton apparel and it completes laundry processing by drying garments for storage and delivery. This is accomplished as conditions are created that allow fabric to regain smoothness. Best tunnel finished appearance requires moisture from live steam to relax cotton fibres, fabric temperatures of 125 to 135 deg C, to soften polyester, sufficient time for the entire garment to warm to suggested temperatures and good airflow and agitation to shake out wrinkles.
While agitation is necessary for optimum relaxation of fibres, excessive air turbulence can change garment positions on hangers and produce undesirable wrinkles. Garments from improper hanging can become set during the operation and will be difficult to remove. Once garments leave the tunnel, they should hang free until they’re cool. It is very important to understand that tunnels will not perform miracles. Washing, extracting and drying performances prior to tunnelling are determining factors in finished garment appearance. Neither thermal shock wrinkles nor extraction or other pressure set wrinkles will be removed, even under the best operating conditions of the tunnel. THE BOTTOM LINE
Polyester/cotton garments have much to offer in terms of useful life and quality of appearance. Designed to take advantage of the best of both fibres, they combine most of the comfort and absorbency of cotton with the colour retention, shrinkage control, wrinkle resistance, strength and durability of polyester. For these reasons Poly/cotton garments are the preferred fabric option for the Textile Rental suppliers. To fully realise these advantages, care is taken in the laundry maintenance process to properly handle all garments whether cotton or blend. With care, both type of garments will be processed time and time again providing clean, good looking and wrinkle free garments. OTHER PRODUCTS While the notes on the laundry process here, mainly refer to the washing of garments, the same principals apply to all textile products, whether Cloth Roll Towels, Mats, Garments or other textile products we produce. The correct handling of each stage in the process is crucial in providing quality, profitable services. |
