According to Mayer, that is water, shellac and borax.
Although @walrus answered your question perfectly, I would like to address the other issue: where to find a painting medium that isn’t a varnish.
If you are really interested in painting, then I must recommend that you treat yourself to a recent edition of The Artist’s Handbook by Ralph Mayer. You can find used ones on amazon or even at pretty much any used bookstore.
I assume you are using acrylic paints, because you would probably have problems mixing the weepage of India ink with oil-based emulsions. Technically speaking you can mix water-based varnishes with acrylic paints, however my favorite glazing medium is for oil-based painting called stand oil.
According to Mayer, it is a cooked linseed oil that has the consistency of honey and when mixed with turpentine is paler than pure (cold-pressed) linseed oil. When diluted it is “one of the most useful ingredients of glazing or painting mediums”. I know from experience that he is right. Check it out.
If you really want to mix that weepage with oil paint, you can use egg-yolk (or soy lecithin) as an emulsifier.