After scouring ancient texts like Tiangong Kaiwu, I learned that traditional ink was made with pine resin to prevent insects and herbal ingredients to inhibit bacterial growth. However, modern mass-produced ink has largely abandoned these natural components. What about the culprit? The animal glue and chemical preservatives found in traditional ink—when exposed to humidity, they become a breeding ground for mold, much like fermented dough, releasing foul odors.