Pigment Behavior During the Mulling and Grinding Stage

When pigments are combined with a suitable binder, they do not all enter the same subsequent state. After mixing, some pigments form a relatively uniform system without visible powder or clusters. Other pigments continue to show clumps, fine particles, or incompletely bound powder. Grinding is therefore not a mandatory stage for all four categories of pigments, but a subsequent material process determined by the specific state of the pigment after entering the binding system.

Metals and chameleon pigments usually form a relatively uniform state after thorough mixing, requiring no significant further grinding. The pigments that require continued observation during this process are primarily standard artist pigments and certain fluorescent pigments.

1. Clumping and Grinding Paths in Standard Artist Pigments

When standard artist pigments enter a binder, some form hidden clusters inside the liquid. These clumps are not always directly visible on the liquid surface. Visually, the mixture may appear smooth, but distinct structures differing from the surrounding liquid can still be felt during mechanical action.

The material progression at this stage presents as follows: Powder enters binder → Localized aggregation → Cluster formation → Clusters persist inside the liquid.

The degree of clumping varies between pigments. Some aggregated structures break down easily with further dispersion, while others remain stable. Clumping does not automatically mean that grinding must continue:

• Larger aggregates: Noticeably decrease after further mechanical dispersion, eventually forming a relatively uniform state.
• Fine powder or fine aggregates: Remain present even after initial processing, requiring continued mechanical action.

Certain standard pigments combine with binders very slowly. Even after extended stirring, unbound powder may remain inside the system. When entering the grinding stage, these pigments show a more sustained mechanical response. Through repeated mechanical action, the state of the powder, particles, and clumps gradually changes, though the time required to reach a stable state varies. Grinding time itself is an observational variable determined by pigment properties.

2. Differences in Response Between Grinding Tools and Pigments

Different grinding tools do not produce the same material response across all pigments. Some tools exert a clear mechanical force on larger clumps, causing aggregates to break down. However, for extremely fine pigment particles, altering the clump structure does not mean the pigment has fully integrated into the binder system. In such cases, a larger contact area between the tool and material is needed to observe further changes in pigment state.

The grinding tool itself acts as a variable. Different pigments exhibit distinct material responses when brought into contact with different mechanical tools.

3. Physical and Sensory Changes During Grinding

(1) Thin-Layer Drying and Adhesion

Grinding does not occur in a completely static liquid system. When the pigment and binder mixture is spread across a surface, thinner liquid zones gradually dry as water evaporates. Changes appear first along the edges: Edge thins → Drying begins → Crust forms → Solid edge develops.

Once fully dry, thin pigment layers develop strong adhesion, forming hard or sticky structures. This phenomenon indicates that grinding behavior occurs not only between the tool and the liquid, but also between the pigment and the slab.

(2) Resistance Feedback and Mechanical Transfer

Grinding resistance is the combined result of three contact interfaces: Tool ↔ Pigment, Pigment ↔ Slab, and Tool ↔ Slab. Applied mechanical pressure acts directly on this system, transferring resistance back through the tool to the hand. This provides physical feedback regarding thickness, graininess, clumping, dryness, and movement smoothness.

(3) Acoustic Features and Influencing Factors

Friction between the pigment, tool, and slab creates auditory feedback. Coarse particles produce noticeable friction and pronounced sound, while finer powders generate weaker friction and subtle sound.

This sound is determined by particle structure, coarseness, slab material, tool material and shape, contact area, applied pressure, and moisture levels. As water evaporates and the mixture thickens or dries locally, the friction sound changes accordingly.

(4) Odor and Spatial Reaction

Spreading pigment across a surface increases its exposure to air, making inherent odors more noticeable than when confined in a container. Odor intensity varies by pigment, and changes in odor can indirectly influence physical positioning, such as standing further back.

(5) Bubble Formation and Volume Changes

Some pigments readily incorporate air under mechanical action, causing bubbles to form inside the liquid and temporarily increasing visible volume. This phenomenon continues the bubble behavior observed during the initial mixing stage.

4. Grinding Characteristics of Fluorescent Pigments

Some fluorescent pigments achieve a uniform state after mixing and do not require significant grinding. Others contain finer particles or bind incompletely, requiring further mechanical dispersion similar to standard artist pigments.

Fluorescent pigments exhibit the following grinding traits:

1. Particle structures are relatively fine, typically producing weaker mechanical friction sound under identical system variables.
2. Bubble formation can be particularly prominent during grinding, as mechanical action continues to introduce air or alter existing bubble structures.

5. Surface Staining, Powder Dispersion, and Material Transfer

(1) Surface Staining and Expanding Contact

Wet pigments leave color on tools and surfaces upon contact. The grinding process expands the contact footprint of the pigment, creating multiple relationships: Pigment–Binder, Pigment–Tool, Pigment–Slab, and skin contact.

(2) Reduction of Powder Dispersion

Once most pigment enters the binding system, airborne powder dispersion drops significantly compared to the dry powder stage. However, if unbound fine powder remains, mechanical action can still cause minor airborne dust.

(3) Transfer, Residue, and Subsequent Effects

Moving ground pigment into containers can cause stringing, sticking, or dripping due to its viscous nature. Thin layers remaining on the slab or tool dry into crusts over time:

• Residue Interference: Residual color left on the slab or tool (especially contrasting colors) acts as a variable that interferes with subsequent pigment observations.
• Re-activation by Water: Dry residues re-hydrate and show renewed mobility or detachment when exposed to water again.

After entering the container, behaviors such as wall adhesion, local residue, liquidity shifts, ongoing drying, settling, or gas generation continue. The sealed container environment actively participates in these subsequent changes.

6. Multi-Sensory Engagement and the Role of the Grinding Stage

The grinding stage provides integrated feedback across multiple senses:

• Visual: Powder residue, clumping, liquid thickness, drying edges, surface crusting, bubbles.
• Tactile: Resistance shifts, particle coarseness, material changes during dispersion.
• Auditory: Friction sound variations across coarse vs. fine particles and contact surfaces.
• Olfactory: Odor release intensity from pigments and binders.

(1) Summary of Grinding Paths by Pigment Type

1. Standard Artist Pigments: Binding → Clumping → Mechanical Dispersion → Sustained Grinding (for some) → Dry Edge Formation → Ongoing State Observation.
2. Metallic & Chameleon Pigments: Binding → Uniform Mixing → No Significant Grinding Stage.
3. Fluorescent Pigments: Binding → Residual Powder/Clumping (in some) → Further Grinding → Ongoing Bubble Formation → Drying & Crusting.

(2) Essence and Boundaries of the Grinding Stage

Grinding involves complex, overlapping phenomena: aggregate breakdown, further binder integration, internal liquid restructuring, air entrapment, surface friction, moisture evaporation, odor emission, and tactile resistance. It is far more than simply "making particles smaller."

Grinding duration reflects the time required for a specific pigment to reach a stable state under specific binder, tool, and mechanical conditions. It is determined by physical traits such as particle structure, density, wettability, and binding degree. Grinding time does not directly correlate with final paint quality.

The grinding stage acts as a transitional bridge in the handmade paintmaking process, connecting dry powder, binder integration, clumping, mechanical milling, thin-layer drying, surface residue, container transfer, and long-term storage observation.

Over the years, the behavior of different pigments has been observed and recorded through the process of making handmade watercolor paints. Video recordings of part of this content have been archived in the pigment behavior records. The results of these pigment behaviors are organized and presented as art materials on VHaquarell.