A study of softness standard samples using a tissue softness analyzer and hand-felt panels

Since 2011, we have published four research papers in TAPPI Journal. In this fifth paper, we summarize information from the 2023 study, use experimental data collected in 2019 and 2021, and examine methodologies for generating onsite, employee-qualified standard samples for timely quality management. We accomplished three objectives. First, four qualified standard samples were successfully generated for high, medium, and low softness levels in intervals surpassing statistically significant variance (TSA-HF ≥ 2.0, CHF-bulk ≥ 2.4, CHF-surface ≥ 2.6). The three correlation coefficients (R2) — panel-corrected hand-felt bulk softness (CHF-bulk), panel-corrected hand-felt surface softness (CHF-surface), and total tensile strength (TTS) — showed high correlation to analyzed softness (TSA-HF) (CHF-bulk: 0.9789, CHF-surface: 0.995, TTS: 0.975), suggesting these could facilitate identification of hand-felt pair-wise comparisons, as well as instrument calibration. Second, based on extensive practical experience on production lines, we know that certain areas demand special attention when collecting standard samples, including base paper, following the Yankee dryer and semi-finished and finished products following the processing machines. Third, with confirmation for TSA-HF and Panel-HF, we can produce qualified standard samples with more uniform qualities, enabling well-trained quality inspectors to perform their tasks on time.