Share 'Blackening Wood Strips for Purfling?'

Hi Have a 70s Granada from Japan with a minor crush in the lower bout. Need to replace about a 4" section of six layer purfling (WhBlWhBlWhBl) that is totally missing. Managed to work out a way to get 0.015 thick strips, but having trouble getting a deep enough black. Black wood stain, india ink, soaking in iron/vinegar solution; all work to a degree but are either not black enough, or don't…