I have some old tins of litho ink that I thought I would try out and found that it is a lot thicker than letterpress ink. An ink technician advised me that it needs thinning with linseed oil for use on letterpress.
I’m hand rolling so it is only a small quantity at a time. Can anybody suggest a suitable ratio linseed to add : ink that works for them?
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i try not to add anything to the ink, van son sells a tack reducer that will thin your ink.
Start by mixing to the consistency of heavy molasses. It will slowly run off the knife. Experiment to find a mix that you like. I use a product called Sterling Varnish - it’s boiled linseed oil for use as an ink dryer/thinner.
If you are using boiled linseed oil, a few drops will open up an ink which is too thick. Make certain you mix the ink thoroughly. There are a lot of options to reduce the viscosity of the ink. If you have boiled oil, that would be a good start. You may find that it extends the drying time of the ink a bit, but that may be a benefit, depending on what type of ink it actually is.
Be aware that some inks are “thixotropic”. That means that the viscosity reduces as the ink is moved around and transfered to the rollers and ink train. Even an ink which seems pretty stiff in the can will behave somewhat differently when on the press.
I was taught to work all ink on a slab with an ink knife before putting it in the ink fountain. That is how you test the ink’s characteristics (and if skinned over, the only way to remove all the hickeys before they contaminate everything).
Thixotropy is a basic condition of any printing inks used by the people on this forum. Brand new inks may flow easily, but most will age into solidity. Oil base inks may be worked back into useability decades later (fresh driers should be added), but rubber and soy and acrylic inks may just thicken beyond all attempts at reviving.
In general, sheetfed offfset litho inks and letterpress inks aren’t that different; even at the peak of letterpress the differences were mainly in a higher pigment load for offset, and water-resistant varnish, resulting in a higher cost for offset inks. The differences in body were not great between offset and cylinder letterpress inks, but stiffer bodies were needed for platen inks, especially for bond papers.
If you are talking about litho printmaking inks rather than offset litho, that is something else.
I guess it all depends on what kind of ink it is. If it’s rubber based, the I’d use whatever the ink maker recommends….. or toss it. i’m not a big fan of rubber-based ink for letterpress. The most common ones in use at most small litho shops tend to fade badly.
If it’s ol based, then it’s easy to work with. Try a few drops of boiled linseed oil, or Stand Oil from the art supply house. Just use a little bit and mix it well.
Sterling Perfect Print Varnish is a product of Sterling Company in Jacksonville Florida. It works with rubber based and oil based inks. I have used it with rubber based ink that is so old and hard it will bounce!