Choosing colours for blending skin tones with pastels - "Caitlin" WIP1-4

How do you create the appearance of human skin in portraits? Is it possible to use an opaque medium such as pastel to create the subtle hues and tones of skin? What colours do you use, and how do you select them?

I must confess, this is only the second 'human portrait' I've ever attempted, and the first in pastel. My subject is my beautiful little niece Caitlin - her birthday is coming up, so I'm painting this portrait as a gift. The paper is ivory Mi-Teintes Tex A3, and the pastels I'm using are Schmincke soft pastels and Faber Castell PITT pastel pencils.

When in doubt about choosing colours for my 'realistic' paintings, I use a relatively fail-safe method to start with. I open the photo in Adobe Photoshop, and use the 'eyedropper' tool to select areas of the photo's intrinsic colour. I then open a new image and fill the image with the colour I've selected. I compare the large colour swatch on the screen with my palette of pastel colours and select appropriate pastel sticks. An alternative to this method is simply printing the photo out, but remember that there can be differences both in the display of colours on your monitor, and the way these print out with different printers. Invariably the colour swatch appears darker than I imagined the area to be when simply looking at the original photo. I'm not sure why this happens, and it may be a feature of the way our eyes adjust and 'expose' for scenes of variable light intensity.

I started this portrait by blocking in the base layer colours (see WIP 1). I wanted to fill the cavities of the grain of the paper (with a texture similar to fine sandpaper) with shadow colours to create a sense of skin semi-transparency. The colours I picked were all the lightest tints of each hue (M and O tints in the Schmincke range), despite the shadows appearing relatively dark - I wanted the portrait to have a 'baby-soft' feel to it, which necessitated muting the contrast and darks, and keeping the colour set relatively 'warm'. These included the ochres, olives and siennas from the Schmincke range.

In WIP 2 you can see that I've blocked out more of these base colours, along with placing the facial features (eyes, nose, mouth) and adding some detail to them. The base colours provide the ground for building form in the image through the addition of highlights (that is, I was working from shadow to highlight). At this stage I used pastel pencil for outlining the sketched features, and soft pastels for blocking in. You can see that I've started to add the highlights to the forehead region.

One of the benefits of working from dark to light I found is that layering in this way can give you more subtle gradations of colour, and more lifelike colours than if you blocked colours directly, without layering (see WIP 3). Although individual pastel hues may appear very similar when seen on a large chart, you start to really appreciate their differences when layering for skin tones; one hue generally does not transition smoothly into another - too much yellow, too little pink, not dark enough etc. By layering pastels you can give the skin a sense of depth.

I went further than this, however, because I wanted a smooth base layer of colour (with appropriate colour gradations) to add detail to for the final portrait - and for the softness of a baby's face, I blended the colours with my fingers (see WIP 4). Since my niece is actually quite pale in complexion, adding the highlights on top of the darks retained their strength even when blended. I added to this effect by using complementary colours (pale blues and greens) in some of the highlight areas. The next step is adding a final layer of colour and shadows to bring out the form.