1-bit image is gray

I'm working through a proof of concept, and we are thinking of using Batik as a means to work with SVG.  One of the problems we're having is that when we transcode to PNG, the image is always gray.  Our goal is a 1-bit image which is black and white.  Instead, the image is white and some form of gray.
Specifically we call for a new PNGTranscoder(), set the index hint, background hint, and ask it to transcode.  The svg is nothing but text segments and tspans.  We have even tried specifying black text to no avail.  Note that this is all using 1.7.
Any suggestions on a possible means to set, hint, or force the colors in the palette to 0 and 255 (-1)?