Observing Material Fluidity: From Alcohol-Based Inks and Water-Based Paints to Oil Pastels

1. Surface Flow Performance of Common Painting Materials in Different States

Alcohol-Based Ink and Clear Water

When observed on non-absorbent surfaces like smooth plastic, glass, or metal:

• Alcohol-Based Ink: Shows extremely high spreading speed and movement area. The liquid expands outward rapidly upon contact with the surface.
• Clear Water: Also possesses high movement ability, but tends to gather locally or form droplets due to noticeable attachment to the surface. Its spreading speed and evenness are slightly lower than those of alcohol-based ink.

Liquid Paste of Handmade Watercolors

Handmade watercolors are made by mixing pigments, binding systems, and water. Their flow performance is not uniform and is directly affected by the characteristics of different pigments:

• Metallic and Chameleon Pastes: Generally show relatively high movement ability, spreading easily across the surface.
• Standard Pigment Pastes: Show clear internal differences. Earth tones, blacks, and pastes with mineral-like properties are thicker, encounter higher movement resistance, and move more slowly.
• Fluorescent Pastes: Possess good movement ability, but come with stronger stickiness, easily clinging to container walls or mixing tools.

Acrylic Paint and Adjustment States

• Unadjusted State: Acrylic paint without added water exists as a high-viscosity paste. Its own flow capability is extremely low, and it cannot spread widely on its own. The initial thickness and resistance differ noticeably across different brands and colors.
• Adjusted with Water or Mediums: Adding water or liquid mediums reduces the paint's thickness, visibly increasing its spreading and movement ability. The extent of this increase depends on the type and amount of medium added, as well as the initial state of the acrylic paint.

The Solid Behavior of Oil Pastels

In a quiet state at room temperature, oil pastels stay solid and do not spread like liquids. However, when tools are used to apply pressure, scrape, push, or blend them continuously, the material softens locally and changes shape. It does not turn into a liquid, but enters a workable state that makes it easy to reshape.

2. How Contact Surfaces Change Flow Behavior

The flow behavior of materials depends heavily on the absorption properties of the surface:

• Non-Absorbent Surfaces (Glass, Plastic): Liquids can spread freely across the surface, allowing their full movement path to be observed.
• Highly Absorbent Surfaces (Paper Towels, Tissues, Absorbent Paper): When alcohol-based ink or water touches these surfaces, the liquid is drawn into the material instantly. What was surface spreading instantly turns into penetration and absorption.

Talking about the flow capability of a material without accounting for surface absorption is not objective.

3. Dynamic Changes Caused by Manual Operation and Tools

Manual intervention directly alters how a material behaves:

• Changing the Tilt Angle: On a non-absorbent surface, tilting a flat test surface causes gravity to pull the alcohol-based ink or water, noticeably increasing its movement speed and shifting its direction.
• Changing the Mixing Ratio: Adding liquid mediums to thick unadjusted acrylic paste, or adding water to soften solid watercolor cakes, directly transforms low-flow or non-flowing materials into flowing liquids.
• Applying Mechanical Force: Using tools to scrape, drag, or mix oil pastels softens their texture and changes their shape, opening up a workable space for ongoing adjustment.

4. How Environment and Time Affect Flow States

Open air, temperature, and humidity continuously alter a material's flow ability over time:

The Irreversible Drying Process (Ink, Watercolor, Acrylic)

When exposed to air, most liquid systems follow an irreversible path from flowing to completely losing flow:

• Alcohol-Based Ink: As the solvent evaporates into the air, movement stops entirely. This process cannot be undone.
• Watercolor and Acrylic: As water evaporates and the layer hardens, the materials turn into a solid film or dry state, and surface flow disappears completely.

The Long-Term Workable State (Oil Pastels)

Unlike the irreversible state of fully dried watercolor or acrylic, oil pastels do not go through a traditional liquid drying stage if no surface fixative is applied. At room temperature, they remain in a state that can always be softened, reshaped, and adjusted again with tools.

5. Side-by-Side Comparison of Physical Behaviors and Flow Properties