I teach twice a year at Don Messec's workshops. He's using ConeColor PRO Matte Black for the direct plate gravure. He has access to all the Piezography ink sets - including our fully opaque shade 1 and even the Piezography Digital Negative ink sets.
But, he finds that the ConeColor PRO MK works best for his direct plate process including over the Epson MK.
He is very accessible and you can contact him at Making Art Safely, Santa FE, NM
regards,
Jon Cone