using pigments for etching inks - why are some so sticky

[freedda]

I'm experimenting with using some of the NP pigments for etching inks. Some are mixing up quite nicely and I'm anxious to try them on my plates/prints.

Some I've found are extremely sticky, maybe more so than I want, making them very hard to wipe on the plate. Two that I found this with so far are the Vincenza White and Green Raw Umber.

I'm wondering why the viscosity of these is so different than many of the other pigments? My uneducated guess is that maybe they contain more clay-like material which accounts for their stickiness? Again, that's just a guess.

Any thoughts on why this might be are welcome? Or what I might do to address this?

Regards, David

[George O'Hanlon]

Stickiness or tackiness in paint and ink are usually the result of using polymerized oils. However, some pigments may impart some tack to paint and ink. I would be interested in knowing which ones you found gave it the tackiness and also to know what oil you were using to make etching inks.

[freedda]

George, thanks for info. on this an other posts.

I'm using Akua etching ink transparent base, which is the oil base they add pigments to for their inks. It is soy oil based, not linseed oil like most other etching inks. I assume its cooked like linseed oil, but I don't know about it being polymerized?

So far I've found the Italian Yellow Earth to work well when mixed with the Akua base. The Raw Green Umber is very tacky--which is often a good thing in etching inks--but in this case, by the time I've gotten the plate wiped, most all of the ink is no longer in the 'grooves' on the plate. I love the color of the Vincenze White, but it also seems too sticky, though it may serve to mix with other inks.

The Akua Raw Umber is much browner, not green at all, so I was really looking forward to an ink made with your Raw Green Umber.

I'm guessing that I can only get so far mixing the inks by hand with a muller. A roller mill would make better ink I believe, but that's not an option right now. Also, I'm just beginning to work with these and the jury is really still out on this. I'll keep you posted.

Best, David

[George O'Hanlon]

Another cause for the stickiness of some pigments, which is specially true for earth pigments, is the clay content of the pigment. This may cause the sensation of "stickiness." Vincenza White is essentially a clay.

[freedda]

Yes, I was thinking this might be the case. Thanks again for all the info.

Vincenza White is essentially a clay. [/QB]