Two issues have arisen lately amongst those who discuss oil painting, that ever fertile field of controversy, one of which has been raised by Thomas (our resident skinhead) on the Forum. Mediums (Thomas's point) is one - what do you mix with the paint to make it workable? Should your medium include a varnish, to add richness and sheen? What about stand-oil and sun-thickened Linseed oil? Or Beeswax? Or poppy oil? Or Walnut oil? Or gold size? Or cobalt driers? Or ..... and you can go on all day with these questions. It puzzles me slightly that people keep asking them, because half the time I think the mediums are a solution in earnest search of a problem. Do we really find our oil paint so stiff, unresponsive, or just plain dull, that it requires the addition of glossy mediums? Is it so vitally necessary that paint should dry within a week that we really need to add drying mediums to it? Oil paint is almost always mixed, these days, with linseed oil, or safflower oil, in its manufacture. Some colours, notably Titanium White, Zinc White, Alizarin Crimson, Cadmium Yellow and Red, Ultramarine, are generally extremely fluid because they take a lot of oil in the manufacturing process: adding extra oil to some of these is a bit like pouring oil on a slick - why would you do it? I suspect that a lot of mediums are added because we think we should, not because we actually need to. So when asked this question, my advice (and I may not be a great painter, but I do have 50 years' worth of experience of painting in oil) is keep it simple, and don't add ANY medium unless your paint seems to be lacking something; and first examine WHY it might be lacking something. What might that something be? It could be you're using a brand of paint which just isn't meant for you - a very "short" paint, as opposed to more fluid ones. In the dear, dead days it was fairly easy to address this - you just suggested people try Reeves oil paint, rather than George Rowney & Sons'. There was more oil in Reeves' paints, and the Rowney paints, certainly their artists' quality ones but also their old Georgian range tended (and still do tend) to be (to me) satisfactorily less slick. These days, the choice is a lot more complicated and extensive than that, and I'm not sure I'd recommend Reeves' paints anymore, not least because I never seem to see them.... I think they're still made (memo to self: research this!) but they don't have the position in the market they once had. There are paints now ground in different oils, and there are more mediums - some of them dug up by keen artists who are seeking the genuine old master look. Do remember, though, that those old master paintings have suffered the more extensively from the ravages of time the more mediums with which the artist experimented. Joshua Reynolds' paintings, for example, have all but jumped off the canvas in some cases because of the stuff he mixed with the paint. Eighteenth and nineteenth century painting mediums have caused far more harm than good in many cases, especially on flexible supports. Maroger's medium is one I've seen discussed as worth trying again; Ralph Mayer's recommendation to use dammar varnish with the oil and turps has re-surfaced.... If your paint sinks into the canvas or board, it isn't because it needed a dollop of this old jollop: it's because you could have over-thinned it with turps or white spirit - it takes very little mineral spirit, whatever you use, to thin oil paint - or because your canvas or board is too absorbent and sucks up the oil. It might also be because you're using an underbound, badly-made oil paint - in which case, you need to move on to a better brand. Or it might just happen: especially if you've been working on a painting for a while. But if it does, there are better means of remedying it than glugging oil into every mix (rubbing over the area of dull paint with painting medium works). Always remember, there's already oil IN the paint - it hardly ever needs very much more in general applications. Others may suggest all sorts of things, but my advice remains, you'll be ecstatic to hear, gloriously consistent. In the early layers, certainly in the initial lay-out, use your preferred thinner (please not cheap turps or white spirit: they stink, they're bad for you, and they contain impurities which are bad for the paint). As you add layers, you may well find that your paint needs a little help to make it workable - then try something straightforward and simple, rather than an antiquated medium you've found in an old book. Half and half Linseed oil (ie artists' quality, again not the stuff you'd use on your cricket bat) and turps is usually more than adequate; and very little of it. A medium I use quite often is Winsor and Newton's oil painting medium, but only if it's needed. And either medium will be good for adding those twiggy details to your tree paintings. Many of your paintings will be started and finished this way, alla prima, and unless you're going for really detailed work the above is likely to be all you need. But then we come to glazing: the addition of a transparent colour over another, usually a darker over a lighter, giving you (hopefully) something akin to the look of stained glass windows. There are so many things you could use here, and you probably do need something because the glaze colour needs to be oil rich, and thin. In the old days, you might use one of these 19th century mediums, or copal oil - copal oil was extremely popular when I were a lad, but a) it's hard to find now, and b) good! Because it darkened the paint over time. It has been replaced by Liquin, in its various forms. Liquin has many uses - it can be used as a straightforward painting medium, though I've yet to be convinced that it's any better for that than my turps/oil mix. It's good for glazing, because it's thixotropic - in the bottle, it's gloop; shaken up, it becomes liquid (it takes a LOT of shaking to make it very liquid - so you can choose the consistency you want). It holds brush-marks to some extent, though tends to smooth them out; and it sits where you put it; it doesn't run off the canvas. Or you can use stand oil, or sun-thickened linseed oil - this can be bought, or you can make it yourself (many recipes on the internet). This oil has a very rich surface, and it requires practice in handling. But it's technically sound to use it in later layers - not in the early ones. There are other mediums - many others. Try 'em if you'd like, and do report back on your experience. But I think you'll find that most of them aren't necessary, or even very helpful; and some of them are downright hazardous to the paint film. In particular, don't use mediums incorporating dammar or mastic varnish. It's not that they don't work, but when the painting comes to be cleaned, what does cleaning do? It removes dirty varnish, amongst other things. Well, if you have varnish actually mixed with your paint, it COULD cause problems if that gets removed too - your conservator could be happily rubbing away, only to discover to his horror that part of the painting has disappeared. The other question that has arisen, on the internet elsewhere rather than here, is the old perennial about surfaces. It has been said that canvas is not the ideal surface for oil paint because of the fluctuations in temperature and humidity to which it's subject, and also because canvas can rot. Having taken a long time on the mediums issue, I'll be brief - yup, canvas makes for problems. A safer surface is well-seasoned wood, or even metal. But if you can afford those, I'd really like to meet you and, if possible, marry you, or at least merge our bank accounts. Fact is, though, that we still have a very large number of very old, and very large, paintings on canvas in the world's museums. Be still, thy beating heart - not ideal doesn't mean bad choice; and a lot of people love working on canvas; it's their greatest single painting pleasure. Be aware that canvas isn't eternal - but haven't we all got bigger and better things to worry about?