Throw left over mixture away.”

________

that does depend on what color it is now as lighter or darker, if you have darker, and wanted brighter sharper color, you would have lightened /bleached hair first to blonde/ white / gray values as prequel, then added colour

assumption is that colour sets in thirty minutes, so an hour becomes mute or pointless,

there is mention of use quarter amounts at a time, but that may be specific as roots or touch ups , . if you already have lighter hair, then max of 30 minutes is all one treatment can do,

..

Vidal Sassoon > Runway Red

http://www.vidalsassoon.com/en-US/perman…

“Leave on for 30 minutes (or time indicated by your strand test)