Twentieth century Iranian carpets: investigation of red dye molecules and study of traditional madder dyeing techniques

Red is undoubtedly one of the principal colors in Iranian carpets. During the twentieth century, a golden era for Iranian carpet production and export industry, madder was still one of the primary constituents of the red dyestuff, used according to various dyeing methods which is specific for Iran. Compared to the earlier periods, the said period witnessed a clear increase in the hues of the color red and in the alternation of physical and visual properties. We, therefore, aim to get a better insight into the chemical and physical properties of the component which made it all possible—dyes. To this effect, eighteen red wool samples with various hues were collected from seven Iranian carpets belonging to the aforementioned period (from Ali Mirzaei’s private collection) and analyzed using three techniques: reversed-phase-high-performance liquid chromatography (RP-HPLC-DAD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) and colorimetry. We also studied traditional dying recipes to underpin the scientific process involved. We focused on recipes based on madder, which are mordanted with organic additives such as qarehqurut (a kind of Iranian dairy product; also known as Gharehghorut). These substances, additionally, helped control the acidity of the dyebath; a common technique from the period. The effect of these substances on the hue, the associated red dye chemistry, various visual and physical properties, including color fastness, are reported. Our study revealed, among other facts, that the additive qarehqurut is highly efficient at improving color absorption and at increasing lightfastness. Another salient finding was that, besides madder, various synthetic dye sources were used by the twentieth century “traditional” Iranian red dyeing industry.