Find out how easy it is to transfer from watercolour painting to paintings with oils by starting with the good news; if you can paint well in watercolour then you already have most of the skills you need for classical oil painting.
Despite this, many watercolourists still have the idea that oils are horribly complicated; dispel this myth below!
Burnham Marsh, oil, (90x122cm). This was painted with watercolour-like washes then built up with bodied colour.
What skills are the same for both watercolour and oil painting?
Colour-mixing with oils is easy for the watercolourist, as pigments are the same for both watercolour and oils. If you look at the side of a watercolour tube - let's say, ultramarine blue, for instance - you'll see a little pigment code, in this case PB29. You'll find exactly the same code on the side of an oil tube, which means that if you know how ultramarine blue 'works' in watercolour then you can rest assured it'll be essentially the same in oils.
Ultramarine blue pigment
This means that if you regularly use ultramarine blue in your watercolour mixes, it will create exactly the same colour mixes you've perfected in oils. Extrapolate this to your current paintbox then, if you simply duplicate those colours in oil, all of your watercolour mixing skills can be transferred directly to oil colours.
As a watercolourist you'll know that every technique has an optimum working time or window, usually when the paint or paper is wet enough to achieve the effects you want, but not so wet that they won't stay put. In addition to this some watercolour effects, particularly randomising ones, depend on placing the paint in the right way at the right time to get the best results.
Oil painters call the working properties of oil paint (thickness, liquidity and stickiness/oiliness) its 'rheology' and, just like watercolour, there's an optimum time to work into washes, scratch into wet paint, or achieve a good blend. In this respect oil paints are generally more forgiving than watercolour so, if you can manage the active surface of a full watercolour sheet, then oils should be an absolute breeze.
Traditional oils are very similar (almost identical) in terms of their working window as watercolour, while more contemporary oils, where fatter buttery paint is used, are very different.
I recommend that watercolourists start by trying more traditional oil painting techniques and don't dive straight into using thick blobs of tube oils applied with a knife or square brush.
Stick to your strengths
By building on the skills you have, and using ideas you understand (such as the importance of retaining a glow from the white ground), watercolourists generally exceed their expectations if they try a traditional oil method.
Conversely, when watercolourists take on a more contemporary oil method, they can become overwhelmed by the opacity and stickiness of oils squeezed directly from the tube.
What are the main differences between watercolour and oil painting?
The greatest difference between oils and watercolour is drying time, of course, however if you avoid using fat buttery oils and use a fast-drying medium, such as Galkyd or Liquin, your paints will be workably dry relatively quickly.
Initially, avoid adding extra oil to your tube oil paints in the form of an oil and solvent medium or any kind of oil (linseed, stand, poppy, walnut, or safflower).
Tube paints are already as full as they need to be with oil, and adding more will have disastrous consequences for the drying and handling properties of your paints.
When oil is added to paints by experienced artists, it's generally to facilitate a bit of subtle blending, add a little lustre or retard drying for extended blending; none of these things should be on your to do list yet.
Know you oil painting mediums
You should add oil mediums to your paints instead of pure oil or solvent. Mediums help you to manage the paint's working properties, drying rate and lustre.
When using an oil medium, the most common mistake that watercolourists make is to substitute it for water in their technique.
Oil mediums should generally be added in small quantities to tube paint; if you use too much you'll get into trouble. While oils can be diluted with a little solvent, or a half solvent, half medium mix, it is generally best to apply them as thinly and dryly as possible. When you need to use a wash of oil paints (a glaze), this is generally quite viscous and not at all runny.
A selection of glazing mediums
Discover more in our beginner's guide to oil painting
So why try oils?
Simply put, oils add an extra dimension to your current watercolour skills, specifically opacity. So rather than just applying ultramarine blue in translucent washes, you can opt to lay it down more thickly, or even as a textured paste.
By using just a single colour in glaze, body and impasto (see easy definitions below) you can create many more visual effects than are possible in pure watercolour, and it is this creative potential, which makes oil paints worth learning.
Once you extend your palette to a few colours, oils will open a new creative language in which to work.
Learn the language - oil painting terms explained
- Thin washes are called glazes
- Thicker, more turbid paint is called body colour
- Very thick or textured paint is known as impasto
Various Rheologies. This 30x20ft study after Monet has washes, bodied paint and impasto. It's important to use various consistencies in your work.
An easy oil method for watercolourists
Many great oil painters used watercolour or watercolour techniques in their practice so it makes sense to emulate a few of their methods as you extend your skills to oils. The following is a simple way into oils for watercolourists.
Early oil paintings evolved from tempera paintings, that's to say layers of oil paint laid over an aqueous underpainting such as egg or starch tempera. In this ancient sense, watercolour is a type of distemper (an aqueous paint bound with glue), making it a practical base for oils. There is no reason why you can't apply your watercolours to a canvas prepared with a water-based gesso then build oils up on top of them.
Turner - a wonderful watercolourist - was a great advocate of this method, although I don't recommend that you follow his example of placing waterbased paints over oils, as it subsequently fell off!
Give it a try:
- Prime a canvas with an aqueous (acrylic and chalk) gesso; those sold as ‘suitable for oils or acrylics' are generally fine.
- Paint on it with your watercolour, and allow it to dry.
- Using the same skills, extend it to oil glazes. Note that these won't wash the watercolour off.
- Add slightly thicker, more opaque paint (bodied colour).
- Finally add the thickest most opaque bits (impasto).
You'll note how much richer the colours become with the glazes in Step 3; how some opacity makes your picture more solid at Step 4; and how strong impasto can look at the final stage of the painting.
If you're stuck for inspiration work up a study from Turner, Constable, Sargent, Degas, Cox or any of the great artists who used both watercolours and oils.