I finaly had success with my stubborn gray hair that don't easily absorb color. My use of pure henna would give me this sickly looking copper color I hated and following with indigo was hit or miss. Wet hair didn't work because I'm. Dry didn't work either. I spritzed my hair to be damp. Applied black Surya to the section I have the copper hair. covered with platic cap and scarf and went to bed. Washed it out the next morning and the ugly copper highlight are gone and in place now deep reddish brown.