Digital BW, The Print

I have been using inkjet printers to produce positives to use for 
photoetching. I need the most opaque and consistent black possible to 
block UV light during exposure. If the image uses different colors 
each color has a different opacity to UV light and I get inconsistent 
results. I just bought an epson r300 because I had read of the black 
only option.I have tried printing a grayscale image in black only mode 
on transperant film. The output has a blue tone and when I examine 
with a loupe the dots appear both black and blue. Can I make this 
printer print a consistent black or is this a quality of the standard 
black epson ink?  Does anyone have a recommendation of the best way to 
obtain a very opaque and even black. Also what would be a good set up 
to produce larger positives in terms of printers and producing an 
opaque and consistent black.