Fig. 5From: Early modern knitted caps (fifteenth to sixteenth centuries): analyzing dyes in archaeological samples using microspectrofluorimetry complemented by HPLC–MSExcitation (left spectrum) and emission (right spectrum) of both purpurin and carminic acid aluminum references prepared at a concentration of 10–4 M in methanol:water (70:30, v/v) with Al3+ (× 100) at pH 2.4 (purpurin) and pH 3.5 (carminic acid), applied in filter paper. For more details see [27]Back to article page