Six leather swatches were cut into uniform rectangular samples and divided into two groups, with three swatches assigned to each ink remover. Initial colorimeter measurements were taken using a BYK-Gardner Colorimeter to record L* (lightness), a* (red/green value), and b* (blue/yellow value) before staining (Unstained Fabric), after staining with ink (Untreated Stain), and after treating the stain with the product (Treated Stain).
A black permanent marker was applied to the center of each swatch to create consistent ink stains across all leather samples. Each product was applied to its respective leather swatches directly onto the stained area by the same evaluator using five complete circular motions, followed by a 30-second wait to allow the product to penetrate. The stain was then lightly dabbed once with a clean cloth to remove residual product and any ink loosened by the treatment.
The performance of each ink remover was evaluated instrumentally using the Stain Removal Index (SRI), a scale from 0 to 100, where 0 indicates no stain removal and 100 represents complete stain removal. The SRI was calculated as:
SRI=100×(ΔE∗(US−UF)−ΔE∗(TS−UF))
Where:
- UF = Unstained fabric area
- US = Untreated stain area
- ΔE(US-UF)* = Color difference between the untreated stain and the unstained fabric
- ΔE(TS-UF)* = Color difference between the treated stain and the unstained fabric
The value ΔE (absolute color difference) is calculated as:
ΔE* = √ΔL*2+ Δa*2+ Δb*2
Where:
L = reflectance
a = redness/greenness
b = yellowness/blueness