Stand oil or sun-thickened Linseed oil

Recently, I felt a small oil I'd painted was dull and pedestrian (not the first time I've felt that, but passing rapidly on ....). And so I rummaged within the deepest recesses of the bureau in which I keep ancient mixtures of mediums, varnishes etc, and found my bottle - nearly empty - of stand oil: Linseed oil thickened, in this case, by being left to sit in the bottom of a bottle for years on end until it has attained the consistency of very thick treacle. (Got to be honest: I've had this bottle for nearly 35 years - but you don't need to take anything like as long as that!) I mixed this with transparent colours and applied it to a rather dull, dark patch in one of my paintings - I was, frankly, mesmerized by the result: where I'd had a patch of dull, matte, dark brown paint, I now had a glowing surface of great complexity. I'm not sure how long it'll take to dry, but however long it takes, it'll be worth it. You can buy thickened Linseed Oil, stand oil, sun-thickened oil - but it's easy, if a little long-winded (but not 35 years long-winded), to make your own. Pour a quantity of refined Linseed oil into a container, preferably glass - a small dish would be good. Place a piece of glass over the top of the container, but support it with a few match-sticks - enough to just hold the glass cover over the container, while allowing air to get at it the mix within. Put the container on a window-sill. Give the oil a stir every now and then - doesn't much matter how often, but say every other day. And when you've got a mix the consistency of marmalade, thick-cut, use it with your oils when glazing. It's entirely fantastic; and better, if you make it yourself, than anything you can buy. It will take a while to dry, but then oils do - you just have to get used to that: accelerating drying too much can lead to cracking. I don't think similar results can be obtained with water mixable oils - but if anyone knows better, do let me know. By the way, oils used this way are quite resistant to yellowing. It really is a wonderful experience using oil this way - it's not an Impressionist technique, if that worries anyone; but it can give layers of interest that nothing else can offer.