green verdigris (zangār) mixed with saffron

Ingredients

copper, sal-ammoniac (nošādor), grape vinegar, saffron (za‘farān), yoghurt

Preparation Steps

Original Recipe Text

The study identifies several historical techniques for zangār: 1. Mixing one raṭl of sal-ammoniac (nošādor) and half a raṭl of copper pieces in a bowl with strong grape vinegar, pounded with a camel-hoof-shaped wooden stick (p. 189). 2. Mixing copper pieces and strong old grape vinegar in equal proportions, hanging in a well for forty days (p. 189). 3. Burying thin blades of clean copper in a well in a moist place, pouring unfiltered vinegar over it for a month (p. 189). 4. Using sheep-milk yoghurt instead of vinegar to generate verdigris, which results in a pigment that 'chars paper' unless saffron is added (p. 190).

Evidence

"Of the twenty green pigments analysed, nine were identified as being green, copper-based pigments... whereas two were found to be pure verdigris and three were identified as verdigris mixed with saffron. (p. 191)"

Remarks

The investigation unraveled the mystery of why saffron dye was used to prevent the corrosive effect of green verdigris (zangār). Pure verdigris in manuscripts (e.g., 17th-century Atiqi Collection sample) shows extensive paper charring (Fig. 2b, p. 192). Experimental analysis showed that saffron solution acts as a powerful buffering agent (p. 195). The pH of 1% saffron solution remains stable at 5.5 even with addition of acetic acid (Graph 1, p. 192). This prevents the local formation of alkaline hydroxide active in the final stage of degradation (p. 195). Saffron also helps obtain a popular pistachio green shade (p. 190, 194).