Ink formulation

My typical ink consists of a flux binder, a colorant, and an oil medium.  The flux binder is Ferro 3134 frit (lower melting than 3124).  The colorant is a metal oxide pigment.  As previously mentioned, the oil medium is #8 burnt plate oil (Graphic Chemical).

A typical formulation is 0.6g 3134 frit, 3-4g colorant, and an unmeasured amount of oil.  I heat a dish on the hotplate, pick a gob of #8 from its can with a spoon, and place the spoon into the hot dish.  The oil will thin out and flow more readily into the dish.

To the oil I add portions of the dry mix, stirring with a small stainless steel spatula.  Depending upon the specific colorant, incorporation into the oil can be straightforward or more difficult.  I continue to add dry material to the ink until it feels "right".  This is regrettably difficult to communicate, and I must admit that I am still exploring what works better and what does not.  I hope eventually to be able to give a measured formula with good proportions of oil to dry ingredients.

When cooled, the ink is somewhere between sticky tar and stiffly elastic without much surface tack.  It seems to be best used when first mixed.  Unless stored under water to exclude air, it forms an oxidized skin and performs poorly when reheated.  Even when stored under water, performance seems worse when reheated.

So far, my successful pigments are all from Gamblin.  The safest and most reliable and by far least expensive are the various iron oxides, especially Burnt Umber.  Beautiful but more expensive and arguably more toxic is Cobalt Blue: my favorite.

Viridian is beautiful in the bottle but is more difficult to mix, and dehydrates during firing to much duller chrome green.  Chrome Green would likely be a better choice, but the local art store had only Viridian in stock.

Manganese Violet is beautiful but disappears when fired, working as a flux rather than colorant.  You can see the image as a subtle texture, but not as a color.

Ultramarine is formed in a kiln, but very sadly loses the essential trisulfide from its zeolite cage when fired again, losing its beautiful color.

Some workers have reported using Mason stains in oil.  I have been unable to make a usable ink from Mason stains, though they seem to work well as body colorants.  They incorporate with the oil, but seem gritty, ink the plate poorly, and give only faint density in the transfer.

A risky experiment with Deep Cadmium Red tube oil paint gave a beautifully inked tissue, but very poor transfer to the body.  The transfer and a direct painting-on to the body, disappeared when fired.  Cadmium is cardiotoxic and volatilizes, and that will be the end of my experiments with it.