Among the most consequential and least visible of all the technical decisions made in the production of East Asian painting is the preparation of the silk ground — a process known as sizing, through which raw woven silk was transformed from an absorbent textile into a surface capable of receiving ink and mineral pigment with the precision and control that the gongbi and other fine painting styles demanded. Raw silk, left untreated, absorbs liquid rapidly and unpredictably, causing ink to bleed along the weave of the fabric and making fine linework or controlled washes of color effectively impossible. To counteract this, painters or their assistants prepared a solution of alum — a mineral astringent — dissolved in water, sometimes combined with animal hide glue to add additional body and tooth to the surface. This solution was brushed evenly across the face of the silk in careful, overlapping strokes and allowed to dry, a process that might be repeated multiple times until the desired degree of absorbency had been achieved. The alum reacted chemically with the silk fibers, partially sealing them and creating a surface that would accept ink with a controlled, deliberate flow rather than an uncontrolled bleed — allowing the painter to lay down fine lines, build up successive layers of transparent color wash, and achieve the luminous, jewel-like quality of mineral pigment that distinguishes the finest examples of Chinese court painting. The degree of sizing applied was itself a meaningful technical choice, varying according to the intended style — a heavily sized surface suited the meticulous demands of gongbi fine-line painting, while a more lightly treated or partially absorbent ground might be preferred for looser, more atmospheric work where a degree of controlled bleeding enhanced rather than hindered the final effect.