1. Washing water
The washing water for linen has high requirements for cleanliness and hardness. The water used for linen washing is specially treated washing water.
This is because the water directly extracted from the well or tap water will carry a large amount of yellow mud or fine dust. After these unfiltered water containing silt enters the washing machine, it will cause serious pollution to the linen, resulting in visual gray and yellow. Currently, filtering equipment is generally installed at the front end of pipelines or reservoirs to purify the water source and improve the cleanliness of the washing water, so as to avoid the influence of water quality problems on the quality of linen washing.
At the same time, the water will inevitably contain a large amount of soluble salts or metal ions (such as Ca2+; Ma2+; Fe2+; Fe3+, etc.). The temperature of the washing water can reach about 80 degrees during the main washing process. If it is not treated, these hard Soluble salts of metal ions will decompose at high temperatures to form insoluble salts.
Therefore, the washing water must be softened to ensure the washing quality of the linen.
2. Washing machine
So can we avoid the problem of gray and yellow linen as long as we treat the washing water well?
Don’t worry, you have to pass the level of washing machinery. The large industrial washing machines used in general washing factories will be painted with anti-corrosion coatings, such as ordinary iron red; anti-gray paints, these paints often cannot withstand high temperatures and heat for a long time. The coating will fall off if it is immersed or corroded in a high-alkali and high-chlorine environment.
In this way, the steel parts of the washing machine in contact with water during the washing process will produce a large amount of Fe2+ in the washing water; Fe3+ is mixed during the washing process, then these substances are in addition to the high temperature precipitation mentioned in (1). In addition to the adverse effects caused by gathering on the linen, what effect will it have on the graying and yellowing of the linen?
This requires finding the answer in the post finishing of the linen.
3. Post finishing of linen
The seemingly calm post-finishing of linen actually hides "killing intent".
The steel parts after the protective layer falls off will produce a large amount of Fe2+ under the washing water during the washing process; Fe3+ these elements will adhere to the wet linen during the washing process, so that when the linen enters the finishing drying and ironing process , After the water is heated and volatilized, the trivalent or divalent iron ions will generate iron salts and continue to remain on the linen, causing the linen to turn gray or yellow.
In addition, the heat generated during drying and ironing will also affect the soluble salts in the washing process. In a high temperature environment, the soluble salts will decompose and become insoluble salts, and the newly formed insoluble salts will also adhere to the linen. , After N washings, the linen will turn yellow.