Differences between Pre-shrinking, Washing, and Sand Washing

I. Pre-shrinking

Pre-shrinking is a finishing process that uses physical methods to reduce fabric shrinkage after soaking in water, also known as mechanical pre-shrinking. Pre-shrinking primarily controls the warp shrinkage rate of the fabric. Before pre-shrinking, the warp shrinkage rate is generally 7-8%. After pre-shrinking, the warp shrinkage rate is typically required to meet the national standard of 3% or the US standard of 3%. Due to different drying methods, the US standard requirement is higher; 3% in the US standard is equivalent to 1% in the national standard.

II. Washing

Washing involves adding softener or detergent to water and directly rinsing the fabric. Depending on the washing time and the amount of softener, it is generally divided into light wash, regular wash, and heavy wash. The effect after washing is that the fabric becomes very soft, has a very good hand feel, and may even give the illusion of being thicker.

III. Sand Washing

Sand washing is similar to washing, but the added substances are different. Generally, alkaline or oxidizing agents are added, and a suitable amount of softener may also be added. Adding alkaline auxiliaries is intended to disrupt the fabric's surface structure, making the fabric softer to the touch after sand washing. The surface will also develop some fuzz and a faint white haze. Therefore, sand washing makes the fabric softer, more fuzzy, and gives the illusion of increased thickness. However, such fabric is very prone to splitting and may tear easily with a gentle pull. We generally do not recommend sand washing thin fabrics.