The spin finish content on yarns can be determined through extraction. A soxhlet extraction apparatus is used to do so. A predefined amount of yarn is taken and loaded into an extraction liquid. When the extraction is completed, the extraction liquid is evaporated and a spin finish residue remains ready for analysis. The content is gravimetrically determined. If component analysis is desired NMR or FTIR analysis can be conducted.

A calibration curve is needed for NMR analysis on the spin finish content.