Data-Driven Evaluation of Task-Specific Performance in Refined Watercolor Brush Prototypes Using Repeated-Measures Analysis

Abstract

Watercolor brush performance emerges from the interaction between prototype configuration, bristle characteristics, material transfer, and the requirements of specific painting tasks. This study presents a data-driven evaluation of ten refined watercolor brush prototypes by integrating professional expert validation with controlled repeated-measures performance testing. The study used a sequential two-stage design. In Stage 1, 15 professional watercolor artists evaluated five round-handled and five flat-handled refined prototypes on material quality, grip comfort, movement control, water retention and color distribution, and professional-use potential. The overall expert evaluation mean was 4.65/5.00. In Stage 2, 24 experienced watercolor practitioners tested all ten prototypes across precision, graded-wash, and mixed technical tasks, producing 720 primary trials. Objective outcomes included task completion time, line-deviation error, stroke-width variability, wash-gradient error, wash smoothness, and paint consumption; task-specific usability was recorded after each trial. All 720 outputs were independently rated by three blinded watercolor experts, yielding 2,160 technical-quality ratings. Round configurations showed markedly lower precision error (0.442 vs. 1.243 mm) and shorter precision-task times (48.64 vs. 75.53 s), whereas flat configurations showed lower wash-gradient error (3.43 vs. 13.32 CIE L* units), higher wash smoothness (95.72% vs. 83.35%), and shorter wash-task times (39.40 vs. 67.42 s). Mixed-task differences were substantially smaller. A linear mixed-effects model confirmed a strong family-by-task interaction in completion time, while trial order was not significant (p = 0.512). Subjective control and satisfaction followed the objective task-specific pattern, whereas hand fatigue and wrist discomfort did not differ meaningfully between families. Blinded rating reliability was excellent (ICC(2,1)=0.969; ICC(2,3)=0.990). The findings indicate complementary task-specific specialization rather than universal superiority of one prototype family and demonstrate the value of repeated-measures, multimetric evaluation for data-driven artistic-tool design.