The process of applying sizing to warp yarns to improve their weavability. Weavability refers to the ability of warp yarns to withstand repeated friction, stretching, bending, etc. On warp sheets, heddles, reeds, etc. on a loom without causing excessive fluffing or even breakage. Unsized single yarn fibers do not adhere tightly to each other and have more hairiness on the surface, making it difficult to weave. After sizing, part of the sizing liquid penetrates between the fibers, and the other part sticks to the surface of the warp yarn. The sizing mainly based on the penetration of the slurry into the fibers is called penetrating sizing, and the sizing based mainly on the slurry adhering to the surface of the warp is called covering sizing.
Ancient manual sizing involves spreading the warp yarns into sheets, applying paste with a brush or reed, drying and then winding them into weaving beams. There are pictures and texts about using brushes to sizing warp yarns in 《Nongshu》 written by Wang Zhen of the Yuan Dynasty. The 《Paste Pasting-section in 》 Tiangong Kaiwu - Naifu Chapter" records the methods and tools for using starch, cowhide, and bone glue paste. The emergence of power looms in England at the end of the 18th century separated sizing and weaving into independent processes, and the prototype of the modern sizing machine appeared. After several improvements, in 1853 the British J. The patent of Boroff et al. already has the basic characteristics of the current sizing machine.