Making yellow pigment from oxalis is proving to be a challenge. To make a precipitate, I am adding my alkali solution to the alum sulfate dye solution....turns orange...which is isn't the yellow I want...sure is a fun, bright orange.
It's oxalis season here in the bay area. You will find these low growing 'weeds' with bright florescent blossoms everywhere! I'm collecting flowers to make into yellow pastels and paint, hopefully ready for sale this summer. Make your own dye by collecting flowers, pack into a clear jar and leave outside in the sun for a few days. Makes a great dye on un-mordanted silk, wool or cotton.