I did a test plate using the water-soluble hard-ground, Z*Acryl. I just freehand sketched this goat kid onto the plate feeling out the differences between the way the etching needle cuts into the Z*Acryl hard ground versus the traditional asphaltum-based hard ground. I found that in the areas where my hand was light, the point "skipped" yielding a dotted line. Yet, overall the line was even and thicker than my lines are when using traditional grounds.
In the spirit of fully testing the Z*Acryl products on one plate, I did the aquatint version using the Z*Acryl stop-out. The brush-strokes didn't "spread" the way they can when using traditional hard ground as a stop out. Even when hard ground is mixed with asphaltum to thicken it up, it still is tough to control brushstrokes sometimes. So, there was an advantage to using the Z*Acryl stop out in this regard. However, the Z*Acryl stop-out is a green color that wasn't easy to see on a zinc plate.
I plan to do more experiments with these environmentally-friendly, water-soluble mediums but unfortunately I can't say that I'm ready to give up traditional hard ground yet. There's still nothing like it that I've come across.