The harvest is done - Oil on canvas board (6" x 8") by Benoit Philippe
This post is based on my answer and some further thinking I have done since. I am not going to give you a recipie, but rather discuss different factors that I believe help me to get luminous colours in oil.
Does the brand of paint count? It does and it does not. I am using several brands. Most of my tubes are Winsor & Newton, and I also own a few tubes from reputable brands that are good quality: Blockx, Roberson & Co. and Mussini / Schmicke.
I always use artist quality paint, not student paint (which contains less pigment). This is more important than the brand itself. Always prefer artist quality paint: they will make the painting process easier and the end result look better. Stay away from the cheap unbranded tubes in bargain shops.
Pick the right support and prepare it well. If your support is too absorbent, it will suck-up the oil or resin in the paint and the finish will look dull. Get good quality canvasses. If you paint on MDF, prepare the board with two or three coats of gesso.
Avoid ending-up with muddy colour:
- I am not using any black (in general) and by using a limited palette, I can keep them luminous. I mix my black from Ultramarine blue, Crimson red and a Dark green (like Viridian). I am not saying black is a bad colour; I am just saying that adding black to darken colours will make them dirty and grey.
- I am using Sansodor thinner, which accelerate the drying time of colours (important at an early stage when painting alla prima). I can build-up on the block-in phase without creating mud.
- I am painting thin until the very end. In the last stage, I can add texture and use a painting knife if necessary to get bold strokes.
- When I feel colours are becoming muddy, I stop and let the painting dry before carrying on with the next stage.
Try different painting mediums. Another consideration is the medium I use. I like to finish the painting with a painting medium that has a good consistency and is like syrup. Winsor & Newton has one which is resin based. I have used several brands over the year.
Glazing. Applying a glaze on a dry or semi-dry surface of paint is a sure way to add luminosity to your colours. For obvious reasons, transparent and semi-transparent colours work best for glazing. Check the labels on your tubes.
Varnishing or not varnishing. A coat of varnish will revive the colours. You could use matt varnish for protection, but glossy or satin varnishes will make the surface even and brings out the colours.
I hope this helps.