This experiment exposes second-year undergraduate students taking a course in analytical organic chemistry to high-performance liquid chromatography (HPLC) and quantitative analysis using the internal standard method. This is accomplished using the real-world application of natural dyes for textiles. The extracted flavonoids of the plant weld are responsible for the yellow color of the dyed wool. Dried and ground weld is extracted for dyeing wool and quantifying the plant’s three main flavonoids. The students also mimic the work of chemists investigating historical textiles by carrying out a small-scale extraction of the dyed wool. Twenty-one students carried out the experiment, and their samples were analyzed using either a traditional 5 µm-particle size HPLC column or a modern 1.8 µm-particle size ultrahigh-pressure liquid chromatography (UHPLC) column mounted in a conventional HPLC system.