The removal of food fat based soils during the washing of fabrics

• Equipment and methodology developed to characterise hand washing of clothes.
• Lard deposited onto cotton fabric.
• Cleaning carried out using water and a non-ionic surfactant.
• Cleaning at 10 °C and 25 °C ineffective for conditions examined.
• 50% of lard removed using water at 40 °C; 60% removed using 0.2 g L−1 of surfactant.

The removal of a deposition mass of 8.55 ± 0.43 mg cm−2 of lard from plain-weave cotton fabrics under controlled flow conditions has been investigated using water and a solution containing a non-ionic surfactant. Three distinct flow regimes of cross-flow, through-flow and a 2:1 combination of cross- and through-flow respectively have been studied at three cleaning agent temperatures of 10 °C, 25 °C and 40 °C. The lard removal efficiency has been quantified using weighing and image analysis methods to determine the mass per unit area of lard in the treated region. The hydrodynamic resistance changes of the fouled samples have been monitored during the washing process.A time-dependent colour analysis has been shown to be an effective quantitative method of both showing the kinetics of mass removal and investigating mass re-distribution during cleaning.Computational fluid dynamic simulations have been used to investigate the shear rate distribution on the yarn surface during the flow conditions selected.Results demonstrate that effective removal of lard from fabrics at low temperatures requires a combination of chemical, physical and hydraulic factors as hydrodynamic flow alone is insufficient to ensure complete removal. Trends in hydraulic resistance changes due to fabric swelling during cleaning are also reported.