Watercolor Pigment Filling and Solidification: Morphological Evolution of Standard, Metallic, and Fluorescent Pigments

During the filling and solidification process of watercolor pigments, different types of pigments show clear variations as their state transforms from liquid to solid. From the moment liquid enters the pan to the final formation of a solid structure and long-term storage, the changes in pigments remain in a continuous state of evolution.

In the early stages of filling and drying, standard artist pigments usually display clear characteristics of layered filling and step-by-step drying. These pigments are rarely filled into the pan all at once; instead, they form multiple liquid layers in distinct stages. The drying speed of each layer is influenced by pigment density, particle structure, and the state of the binder system. When fresh liquid is poured in later, the underlying layer that has already begun to dry is re-softened, causing the drying process to evolve in an alternating pattern. As the number of filled layers increases, the internal cycles of re-wetting and re-softening multiply, naturally extending the overall filling timeline. During this progression, if the surface pigment dries noticeably faster than the interior, a relatively smooth skin forms on the outside while the inside remains moist or continues to shrink, leaving internal cavities within the structure. Once fully dry, pigment surfaces present diverse structural variations, including different degrees of texture, bubble marks, shrinkage tracks, cracking, or localized depressions.

In contrast, metallic and chameleon pigments show a brief separation between the liquid pigment and the binder system upon entering the pan. As water evaporates and the binder redistributes, the material eventually settles into a relatively stable structure. During subsequent filling stages for these pigments, the underlying dried layer is rarely re-softened by new liquid. The internal structure remains relatively stable, internal cavities almost never form, and the overall filling timeline is generally shorter. Although trapped air bubbles gradually move upward and settle on the top surface as the interior shrinks—leaving visible local bubble marks—the surface rarely develops severe or complex cracking. Fluorescent pigments display unique behavior regarding gas retention and movement. Air bubbles trapped in the liquid state do not disappear immediately after filling; instead, they gradually gather near the top during standing and drying. A large number of bubbles remaining inside creates numerous voids, reducing the actual density of the solid structure. As a result, while the pan appears full from the outside, the interior retains significant cavity structures. In terms of overall filling timeline, layered drying, shrinkage behavior, and post-drying surface cracking or shrinkage tracks, fluorescent pigments maintain high similarities with standard artist pigments.

The contact and shrinkage of pigments along the inner walls of the pan also exhibit clear changes in form. Light-colored plastic half pans serve not only as containers but also directly participate in the pigment adhesion process. As volume shrinkage occurs, some pigments maintain contact with the wall only on the surface, while others undergo local separation or detach completely from the inner wall. Standard artist pigments and certain fluorescent pigments demonstrate stronger adhesion, penetrating into the plastic wall material itself and causing irreversible staining. Metallic and chameleon pigments, on the other hand, do not easily adhere to or penetrate the pan walls. Every layer of pigment undergoes volume reduction during drying, evolving along a path from liquid state to volume shrinkage, local detachment from inner walls, and finally solid structure formation. When liquid pigment exceeds the pan's capacity and spills down the outer walls, dried residue from standard artist pigments adheres firmly to contact surfaces and is difficult to clean; overflow residue from metallic and chameleon pigments, due to viscosity differences, is much easier to peel away from surfaces after drying.

The completion of solidification does not mark the absolute end of pigment changes; the pigment structure simply enters a new phase of long-term storage and environmental response. In humid environments, certain standard artist pigments and fluorescent pigments can be re-activated by moisture in the air, showing changes in physical state. Metallic and chameleon pigments rarely undergo re-activation under natural room humidity. Under prolonged high temperatures or exposure to sunlight, solid surfaces continue to undergo morphological changes, developing fine surface textures or distinct cracking patterns. As pigments transition from raw powder into the binder liquid and eventually lose moisture during solidification, their original noticeable odor steadily fades. Airborne dusting in the powder state and splattering in the liquid state disappear completely once the solid structure is established, fixing the pigment within the solid matrix. In water-free and dry conditions, solid pigments maintain high structural stability, with water remaining the primary external factor triggering dynamic state changes.