Lightfastness of Wax Crayons Using Red Onion-Skin Lake Pigments

Background

  • Natural pigments sought as eco-friendly alternatives to synthetic dyes.

  • Lake pigments = natural dye + mordant ➜ improved adherence & stability.

  • Red onion (Allium cepa) skins rich in anthocyanins/flavonoids; agricultural waste resource.

  • Lightfastness: resistance to fading under light; critical for art materials.

Research Gap

  • Limited studies on lightfastness of wax crayons containing natural lake pigments, especially from kitchen waste (red onion skins).

Objectives

  • Measure lightfastness of wax crayons colored with red-onion-skin lake pigments after sunlight exposure.
    • T1: 2 weeks2 \text{ weeks} • T2: 4 weeks4 \text{ weeks} • T3: 6 weeks6 \text{ weeks}

  • Determine if lightfastness differences among durations are statistically significant.

Hypothesis

  • H0H_0: No significant difference in lightfastness between T1, T2, T3.

Theoretical Basis

  • Color chemistry: metal complexation stabilizes chromophores.

  • Photodegradation breaks chromophoric bonds ➜ fading.

  • Wax matrix may shield pigment, enhancing lightfastness.

Conceptual Framework (Input → Process → Output)

  • Input: formulation 22.4 g pigment:64.9 g wax base22.4 \text{ g pigment} : 64.9 \text{ g wax base}; exposure groups T1–T3; controlled temperature.

  • Process: synthesize pigment, create wax base, combine, cast, apply sunlight treatments, measure color, dispose waste responsibly.

  • Output: Lightfastness rating (mean ΔE\Delta E vs ASTM / Blue Wool scales).

Key Methods

  • Design: Quasi-experimental pretest–posttest.

  • Sample: purposive use of red-onion skins; 162 g batch per color.

  • Wax base (% of 162 g): stearic acid 30%30\%, carnauba wax 17.7%17.7\%, castor oil 10.7%10.7\%, paraffin 8.85%8.85\%, pigment 13.8%13.8\%.

  • Instruments: color spectrophotometer (Lab* → ΔE\Delta E), digital scale, hot plate, silicone molds.

  • Data analysis: One-way ANOVA via SPSS to test H0H_0.

Significance

  • Supports SDG 12 (responsible consumption) & SDG 4 (education).

  • Benefits: DENR (waste reduction), artists (eco-friendly material), teachers/students (learning & cost savings), future researchers (baseline data).

Scope & Delimitation

  • Focus solely on red-onion-skin lake pigment in paraffin-based crayons.

  • Evaluates sunlight exposure only (2–6 weeks) under controlled temperature; other conditions (humidity, indoor light) excluded.

Essential Definitions

  • Lake pigment: insoluble dye–mordant compound.

  • Lightfastness: color stability under light.

  • Lab* values: L<em>L^<em> (lightness), a</em>a^</em>(red–green),(yellow–blue).

  • ΔE\Delta E: numeric color-difference metric.

Ethical & Quality Assurance

  • Non-toxic materials; no tests on humans/animals.

  • Reliability: consistent procedures & instruments.

  • Validity: method alignment with prior literature; controlled variables.