adafruit/Adafruit-Thermal-Printer-Library — pull request #11 by ennui2342 (2013-10-19 21:47:48+00:00)
Title: Configurable maxChunkHeight

Made the the maximum chunk height configurable through setMaxChunkHeight(int val). Defaults to 255 set in begin()

I found that for dense black images the chunk height needed to be pulled down to 100 to give the printer chance to keep up. See http://forums.adafruit.com/viewtopic.php?f=8&t=38668