Dyeing Silk with Sour Grass

After the rains we have plenty of sour grass growing around in San Jose. Today I decided to do some dyeing. I used the recipe in Sasha Duerr's book, The Handbook of Natural Plant Dyes. White silk organza and a few silk charmeuse scarfs were soaked overnight in alum and cream of tartar. The fabrics came out florescent yellow. I put some cotton and linen test strips in the pot also. After soaking in the dye pot overnight, I washed them in water and gentle soap; the bright yellow turned to an olive green during the rinsing. The cotton and linen that had no mordant stayed yellow.