Robert, can you send me your email address please, better to send to my email which you should have. Or in a PM of course. I did have yours but I can’t locate it. And the useless Artists search facility has you as not in existence! I need to chat regarding a current issue that I know you are involved in.

Great, I’ll Google that thanks, I really would like some - probably sooner than later. Yes Prussian Blue is a great choice for a cool sky, again this is very strong. I suppose Cerulean is another good choice for a cool sky, I’ve just spent £50 on a 40ml tube of Old Holland Cerulean Blue (actually it didn’t cost me anything as I had that Patchings voucher). I’ve tried it and it’s fabulous! Their Cobalt also. Returning to Indanthrene Blue, I have used it in the past on heavy overcast skies, I’ll have a look at this one again, it’s a useful colour and to be honest, one that I’d largely forgotten about - so a helpful blog, to me anyway!

I've got some Michael Harding Cobalt Blue - it's a quite fantastic colour: knocks the various Hues into a cocked hat, and is also far more vibrant than most other makers' Cobalts (at least: those I've tried). I would rarely worry much about this - like you, I'm not looking to replicate nature. Because I couldn't! Still - just now and then I feel this itch for a colour that looks like the blue I see on a warm day - I'm actually using Pthalo on a painting I'm working on at the moment, inspired by the fact that Prussian Blue, which is not so dissimilar, seemed to work well in my most recent one. I've also got some Michael Harding Ultramarine - I won't use that for this one, but it was SO much more intense than other makers' versions that it may well be a happier choice for a future painting. We shall see! I haven't forgotten your lead white question, by the way - I've stockpiled quite a bit of it, so haven't bought any lately; but will do my due diligence and research, and report back...! The Supreme Paint Company would be a good place to look, in the meantime. Google will find.

Indanthrene blue is not widely used as you know Robert, I do have some which I haven’t used in a long time. Why? I don’t know is the answer, maybe I should give it a try again. I do know that it’s very strong and you don’t need a lot of it, not even sure of it’s lightfast qualities, but that may be disputed! In my case I always ask myself ‘Do I want to copy nature exactly as I view it’? You’ll already know my answer of course, being familiar with my work. However, there are times when I do want to get somewhere close, not often but I’ve found that for my Spanish skies (not all obviously), that Cobalt Blue (not that cheap insipid hue), serves as a great starting point. UK skies? well Ultramarine does make sense, not on its own, a touch of Yellow Ochre, Violet, orange, Aliz Crimson etc, not all together! It’s a sound base to start with. I know you hate Ultramarine skies, but it’s not a bad choice as your starting point. I’ll return later perhaps with more suggestions, not that I’m by any means an expert! Phthalo Blue can play an important role when used wisely, I love it.