I’m torn between blue ink that makes originals obvious and black that scans cleaner; my quick tests show 300 dpi OCR accuracy at 97.8% with a Pilot G2 blue vs 98.9% with the same pen in black, and dry times of 6.1s vs 4.4s on 24 lb paper. Has anyone tracked recorder rejections or got a benchmark for optical density/L* thresholds (or % OCR accuracy) at 200/300/600 dpi where blue starts causing trouble?
Hard numbers from my shop notes: at 200 dpi a navy-blue gel (OD ≈0.85, stroke L* ≈32 on 96-bright paper) averaged 95-96% OCR vs the same pen in black at about 98%; at 300 dpi both clear 98%, and at 600 dpi they’re >99.5%. On the recorder side I’ve had zero e-recording rejections for blue, but two mail-in rejections from microfilm counties that specify black-only, so if it’s headed to film or scanned at 200 dpi, use black or a very dark blue and you’ll avoid grief.
From my batch tests (about 1k pages): at 200 dpi OCR averaged 96.1% with navy blue vs 98.6% with black; blue falls below 98% when stroke L* goes past about 40 or OD drops under about 0.85, while at 300 dpi it’s about 98.0% vs 99.1% with blue only wobbling when L* > about 45 or OD < about 0.75; at 600 dpi both are ≥99.5%. Recorder-wise I’ve had 2 rejections in 3 years, both pale royal-blue on deeds scanned bitonal at 200 dpi - switched to navy/pigment blue or 300 dpi grayscale and haven’t had an issue since.