Creating Ink stamp negatives

[papurnix]

Hi All, I own a HP 5230, and I'm trying to use it to create very opaque stamp negatives, but having some trouble with it:

BACKGROUND

I've recently bought a resin stamp maker. If you're not familiar with the way these work: they shine UV light through a stencil (which you create), onto a resin pouch. This hardens the resin, creating a perfect imprint of the stencil, (you then wash away the liquid gel around it) - clever!

To create the stencil you have to print it onto a transparent sheet. You have to be able to set the print settings to the blackest, most opaque possible... any light coming through will harden the resin in places you dont want it to!

MY ISSUE

I've been experimenting with settings for a couple of days now, but I'm still able to see through the print when I hold it up to a light.

ALREADY TRIED

- set print in max DPI

- set print quality to best

- turned on and off HP real life technologies setting

- Tried printing on HP matte brochure professional paper, HP matte presentation paper, other matte inkjet printers

- Printed with black ink only

- printed in photo mode with black overlaid with color

MY QUESTION

Some forums I read suggest increasing the ink density, but I cant see any settings to achieve this... (am i already printing at full density with the MaxDPI setting?)

Is there any other methods to increase the print opaqueness here, or if I buy a different printer, what features should I look out for, for what I'm trying to achieve?

Any thoughts or additional ideas, greatly appreciated!

Thanks