Gum Dichromate Speckling

[jesse-m]

I'm so confused by speckling. Here is my print on HPR before adding the black layer.

Once I coat with black (Daniel Smith Lamp Black) I'm noticing it gets extremely speckled. The coating you see is unexposed. I have relentlessly mixed the solution. First my stock pigment with dichromate, then with the additional gum.

One thing I am noticing is that it seems the most intense on the lightest areas of the print.

Even unexposed, it's extremely difficult, if not impossible, to wash off.

Lastly, I notice similar, but not as intense speckling with cyan and magenta pigments.

 

[koraks]

Some paints just won't work with some printing processes. If this paint gives you problems, try another type. The speckling you see is likely pigment clumping, which is always a risk with dispersed pigments. The dispersion isn't perfectly stable outside the normal conditions the paint is intended for. Some paints (dispersions) work better than others.

You could give Calvin Grier's pigment pastes a try if they can still be purchased currently. They're specifically made for gum and carbon printing.

There's some people on this forum who do or have done a lot of gum printing; they might share their experiences. @Andrew O'Neill comes to mind; perhaps he can tell you which black pigments/paints he has used successfully.