Well here goes, Asphaltum has been used for well over a hundred years as far I know. I buy gallon cans of it and basically a gallon will last a life time . Take a dollop put it in a coffee can or similar container and thin it with mineral spirits, you then have a basic stain the depth of which depends on the amount of mineral spirits you mix with it.
The color of the stain is pure brown ,no red whatsoever, being mixed with mineral spirits it is slow drying and thus very easy to work with. You never see it advertised in paint shops because it is so cheap I suppose they cannot make a profit on it .
I have used it for thirty odd years ,and it can be used under practically any finish .
I use it in two ways ,as a basic stain and as a glaze,primarily the latter. As a stain it will tone mahogany to a walnut color [which is handy because wide walnut boards are nonexistent these days ] and is good for oak and ash and walnut as they stay brown [no redness]. As I make mainly antique repros these days I use it as a glaze to give that antique look . I shun brutalizing pieces with chains and the like . My process is to stain the piece with a conventional stain to get the base color you want, then seal the stain in with a couple of sealer coats ,perhaps shellac or sand and sealer. Then cover the whole thing in a heavy [dark] coat of asphaltum. Now wipe it off with a rag, after which you will see that the basic stain color is a shade or two darker,so bear this in mind when you do the initial basic staining. what you will be left with is asphaltum stain in the wood pores and any crevices. You will note that the moldings will be more noticeable and any details will also show. You can experiment with how much you leave on the piece so you get the desired effect. let it dry and then overcoat it with a clear finish . Prior to overcoating if you think it is too dark take a clean rag with mineral spirits and most will come right off and you can repeat the process.
I forgot, if you question this procedure take two pieces do it on one and not the other and you will see the one has that much more depth and character than the other.
My logic, if you think about it people like antiques because how the look . most of these pieces have lived in dwellings that have had coal fires in the winter with the ensuing coal dust .If you ever lived in this environment the ceilings needed to be repainted almost every year due to the soot generated by the fire . Every time the furniture was dusted or polished this dust was ingrained into the surfaces and left in crevices and moldings .......mjh