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  • 3.1 Introduction

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    • In Pointillé, surface behavior is determined primarily by the mechanical properties of the metal sheet and the preparation of its working surface. Because Pointillé is a displacement-based technique (not material removal), the metal’s ductility, hardness, and surface finish directly influence dot geometry, burr formation, reflectance, and the clarity of decorative patterns.
      Understanding material states and preparing the working surface properly is essential for achieving predictable deformation and visual consistency.

  • 3.2 Metals Commonly Used in Pointillé

    • Different metals respond differently to controlled impacts. This section introduces the typical materials and their relevant physical characteristics.

      3.2.1 Pewter (Tin-based Alloys)

      • Ductility: Very high; ideal for deep craters and prominent burrs.

      • Work-hardening: Minimal; supports repetitive impacts without cracking.

      • Visual outcome: Matte impressions; suitable for matte-background stippling.

      • Typical uses: Historical European domestic ware, armour detailing.

      3.2.2 Silver (Sterling or Fine Silver)

      • Hardness: Medium; requires higher impact force compared to pewter.

      • Plasticity: Good; forms clean craters with crisp burr edges.

      • Visual outcome: Strong specular highlights; excellent for high-contrast patterns.

      • Notes: Requires more precise force control to avoid over-striking.

      3.2.3 Copper & Brass

      • Copper: Ductile, warm-toned, produces smooth-walled impressions.

      • Brass: Harder and springier; reduces burr height but keeps crater shape clear.

      • Typical use: Practice sheets, decorative background texturing.

      3.2.4 Aluminum

      • Softness: High; deforms easily, making it suitable for learners.

      • Surface behavior: Pronounced crater formation but burrs can tear if over-struck.

      • Use case: Ideal for novice training and material-response demonstration.

  • 3.3 Material Properties Relevant to Pointillé

    • Pointillé execution is directly affected by the following physical properties:

      3.3.1 Yield Strength

      Determines the force needed to produce plastic deformation.

      • Low yield strength: Deeper impressions (pewter, aluminum).

      • Higher yield strength: Shallower but more controlled impressions (silver, brass).

      3.3.2 Hardness

      Influences burr formation and crater clarity.

      • Soft metals: Larger burr, softer crater edges.

      • Hard metals: Crisp edge definition, minimal burr.

      3.3.3 Work-Hardening Behavior

      Metals that harden during repeated strikes require:

      • Adjustments in force

      • Intermediate annealing (for silver/copper)

      3.3.4 Surface Friction & Contact Response

      Surface texture affects:

      • Punch stability

      • Angular drift

      • Slippage artifacts

      This is relevant in the PhysX simulation where friction coefficients are material dependent.

  • 3.4 Surface Thickness and Backing Requirements

    • 3.4.1 Metal Sheet Thickness

      • Thin sheets (0.4–0.8 mm):

        • Easy deformation

        • Higher risk of reverse-side imprinting without proper backing

      • Thicker sheets (1.0–1.5 mm):

        • Higher force required

        • More stable burr formation

        • Better for advanced learners

      3.4.2 Backing Surface (Anvil or Support Block)

      A rigid, polished support surface ensures:

      • Correct displacement of metal

      • No reverse-side artifacts

      • Accurate crater geometry

      Materials: polished steel block, hardened bench anvil, or specialized craft anvils.

  • 3.5 Surface Preparation Workflow

    • Proper surface preparation ensures consistent reflectance, predictable deformation, and control over the visual outcome.

      3.5.1 Cleaning

      Before pattern work:

      • Remove grease with alcohol

      • Use a microfiber cloth to avoid scratches

      Purpose: ensures clean burr formation and avoids slippage.

      3.5.2 Surface Flattening

      A slight warp or unevenness can distort crater geometry.
      Flatten using:

      • Nylon mallet

      • Smooth anvil surface

      3.5.3 Polishing Levels

      Different artistic outcomes require different surface finishes:

      • Mirror polish:

        • High reflectance

        • Ideal for decorative highlights

        • Burrs produce strong specular contrast

      • Satin finish:

        • Diffuse reflectance

        • Ideal for stippled backgrounds

        • Reduces glare, supports shading patterns

      3.5.4 Masking & Boundary Marking

      Use light scribe lines, chalk, or low-tack tape to:

      • Indicate pattern boundaries

      • Support spacing and density control

      • Avoid deviations during repetitive impacts

  • 3.6 Material State Changes During Work

    • Pointillé involves micro-plastic deformation, which changes the metal state during practice.

      3.6.1 Work-Hardening Zones

      Repeated impacts produce:

      • Higher local hardness

      • Reduced burr height

      • Increased resistance to deformation

      Learners should be taught to:

      • Adjust impact force progressively

      • Recognize hardening patterns visually and tactically

      3.6.2 Reverse-Side Effects

      Incorrect backing or excessive force can cause:

      • Bulging

      • Sheet distortion

      • Local cracking on harder metals

      Simulation modules reveal these effects through:

      • Stress–strain visualization

      • Surface deformation sequences

      • Incorrect-execution exemplars

  • 3.7 Visual Indicators of Proper Surface Preparation

    • Learners should be able to identify preparation quality by observing:

      3.7.1 Pre-Execution Visual Indicators

      • Uniform reflectance under grazing light

      • No visible scratches or abrasions

      • Clean edges and pattern guides

      3.7.2 Post-Execution Visual Indicators

      Correct preparation results in:

      • Sharp crater edges

      • Burrs of consistent height

      • No unintended material tearing

      • Stable spacing without drift

  • 3.8 Summary

    • This lesson has introduced the mechanical and visual properties of metals used in Pointillé and the importance of thorough surface preparation. By understanding the interplay between material behavior, surface finish, and impact characteristics, learners can produce consistent, historically accurate, and aesthetically refined Pointillé results.
      These principles form the foundation for the execution lessons and simulation-based training in subsequent modules.