Caligo Inks has started producing a non-toxic intaglio ink that is oil-based and safe to wash with water and soap. Compared to the Akua Inks that are also non-toxic but are water based and from what they say "It has a thick consistency with minimal water content." HA!
Now I am not fond the Akua Inks at all. They were very lose and would become transparent, but they did card very fast and did wipe just as fast. But the inks were easily able to be over wiped and it has a smell that I wasn't to fond of either , but that's my own qualms. Now the Akua Inks are good to make proofs but I wouldn't use it for a edition-ing a piece. They say it drys but all the prints that I have used the Akua Inks on are still slightly tacky to the touch. I have prints that are months old that are still tacky. Maybe I'm biased, but the Akua inks just don't have the warmth that I get from traditional oil-based etching ink. But I completely understand about having a non-toxic ink for intaglio, it is needed.
That's why I'm hoping that the Caligo Safe Wash Etching inks will be a better alternative to traditional oil-based inks. I have yet to try these inks but I hope too in the following months.