31371178bichromate processesPT2026-03-30 20:40:06UF31371179bichromate processNDUF31371180bichromated pigment processesNDUF31371181dichromate processesNDBT31340479pigment processesPTNT31409988carbon processPTNT31409992gum bichromate processPTNT31410007FressonPTNT31410011dusting-on processPTNT31410014oil processesPTRT31477686oil printsPT