I. Color Fixing Function
- Principle: During the textile printing process, dyes need to adhere firmly to the fabric fibers to ensure color durability. The aluminum ions in alum can react with dye molecules to form relatively stable chemical bonds. These bonds tightly “lock” the dyes onto the fiber surface, preventing them from falling off during subsequent washing, friction, and other processes. For example, for reactive dyes commonly used on cotton fabrics, after adding an appropriate amount of alum, the binding force between the dye and the fiber is significantly enhanced, resulting in bright and long-lasting printed colors.
- Effect Comparison: Printed fabrics that have not been treated with alum will become dull in color and have blurred patterns after several washes; whereas fabrics with alum for color fixing can still maintain a relatively high saturation of color and clear patterns even after multiple standard washing procedures, greatly improving the quality and service life of textiles.
II. Improving Printing Clarity
- Adjusting the Viscosity of the Printing Paste: Alum can adjust the viscosity of the printing paste to an appropriate range. Too thin a paste tends to bleed on the fabric, causing the edges of the pattern to blur and losing the original design precision; while too thick a paste is difficult to evenly penetrate through the printing stencil or nozzle, resulting in incomplete printing. The addition of alum can optimize the rheological properties of the paste, allowing it to spread evenly on the fabric and accurately present complex and fine patterns. For example, when printing exquisite traditional patterns on silk fabrics, the regulating effect of alum is particularly crucial.
- Preventing the Aggregation of Pigment Particles: The pigment particles in the printing paste sometimes aggregate with each other, affecting the printing effect. Alum can adsorb on the surface of the pigment particles and, through electrostatic repulsion and other effects, prevent particle aggregation, ensuring the stability of the paste, so that each pigment particle can be evenly dispersed in the paste and then print clear and delicate patterns on the fabric.
III. Antibacterial and Antimildew Functions
- Inhibiting Microbial Growth: Textiles are prone to being attacked by microorganisms such as bacteria and molds during daily use and storage. This not only causes unpleasant odors but also may damage the fabric fibers. Alum has certain antibacterial and antimildew properties. Its aluminum ions can interfere with the cell membrane structure and metabolic processes of microorganisms, inhibiting the growth and reproduction of bacteria and molds. Adding alum to the printing coatings of some outdoor textiles that are often in a humid environment, such as tents and sunshades, can effectively extend the service life of textiles and keep them clean and hygienic.
- Environmental Advantages: Compared with some traditional organic antibacterial agents, alum, as an inorganic antibacterial agent, has the advantages of low toxicity and being less likely to cause drug resistance, conforming to the modern concepts of environmental protection and sustainable development and providing strong support for the green production of textiles.
In conclusion, with its multiple functions such as color fixing, improving printing clarity, and antibacterial and antimildew properties, alum has become a favored auxiliary agent in the textile printing process, continuously injecting vitality into the fashionable and gorgeous textile industry.
