How to create skin textures with pastel - "Alpine tree frog" WIP 1-12

Pastel is a great medium for creating the illusion of texture on your subjects - not only is the sanded paper substrate inherently bumpy (to catch and hold pigment without needing fixative), but the dry stick form of the pastel pigment means that it can readily be laid in a patchy and colourful pattern, which is particularly suited to creating the organic 'feel' to animal skin.

I took the reference photo of the subject for this painting while working with alpine tree frogs (Litoria verreauxii alpina) in the course of my PhD degree (James Cook University). I was looking at immunity to the devastating fungal skin disease, chytridiomycosis, which has been causing frog declines and extinctions around the world in the last few decades.

This painting came from my desire to give a personalised gift to my main PhD supervisors - Drs. Lee Skerratt and Lee Berger, to thank them for putting up with me for what felt like many long years! The frogs I worked with most closely seemed an appropriate subject!

Due to my many other commitments, this painting has been several months in the making - so now that I have relinquished the painting to my supervisors (I am currently attending the Wildlife Disease Association International Conference on the Sunshine Coast), now is the time to post the demonstration images. Incidentally, the timing couldn't be better as just yesterday I finally received my PhD degree documents in the mail!

Alpine tree frogs are gorgeous frogs, particularly so when raised from eggs in captivity - skin with bright greens, yellows, oranges and browns.

As usual, I start my wildlife portraits with the focal point, which usually seems to be the animals' eyes.The eyes of frogs are one of their most prominent features, and this particular frog had especially captivating eyes. With a large part of the bulbous globe sitting outside the rest of the bony skull architecture (although it can be drawn inwards when blinking or swallowing), their large pupils and colourful irises make them seem somehow more aware than many other animals. Here I've used my darkest black for the pupil and delineated it with some deep browns and greens of the bordering iris region (see WIP 1).

It's important to achieve a sense of 'moistness' about the eye to make the frog believable as a living creature - this can be difficult with the dry medium of pastel, but is generally achieved through the use of highlights or sharp reflections of light from the surface of the cornea. The shape of these highlights is important to create the impression of a three-dimensional globe. Here I have added a curved highlight with intense white, with a slight halo that overlaps the pupil region (see WIP 2). The overlap helps make the white appear as a reflection rather than part of the iris itself.

The eye stripe (the patch of darker colour that runs from the nares (nostrils) back through the eye and tympanum (external ear indentation)) is a region where I can play with texture and colour. Not only is it darker than the surrounding skin, but the rough variation in its surface lends itself to shadows and colour contrasts created by stippling. One by one I add a multitude of hues - yellows, deep maroon, greens, blues and pinks (see WIP 3).

Once I've coloured the eye stripe, it's time to ensure colour and contrast consistency with the rest of the painting by reflecting some of those elements in other parts of the face and body. I delineate the dark region of the lip and neck, and start to bring the peach and pink colours in underneath the mouth (see WIP 4).

Using rich buttery soft pastels (such as Schmincke or Sennelier brand sticks) on sanded pastel papers (such as Canson Mi-Teintes TEX or Art Spectrum Colourfix) is one of the great pleasures in painting with pastels. Unlike some might think, using pastels is very unlike fingernails on a chalkboard, and much more akin to buttering bread (with the right materials, of course).

The special primers used on sanded papers (this is not actually the 'sand-paper' you buy at the hardware store, but a little bit like it) provide a minutely bumpy or rough surface within which pastel granules adhere. Their 'sanded' texture tends to be much greater than ordinary art paper or copy paper, from which pastel colour tends to brush or blow off easily (even during the process of spraying fixative!).

This means that sometimes more than one layer of pastel colour can be applied before completely filling the paper grain. This ability to layer colour can lend itself to a lot of interesting effects, including mixed media combinations where either watercolour or oil colours are applied first to colour the ground. Where paper colour shows through, it can lend unity to a pastel painting.

In this painting I'm just layering pastel by itself, but mostly to get the right texture and combination of hues for the frog's skin. In WIP 5 I've used a pale creamy-yellow pastel to provide some base colour for the skin of the lip of the frog.

After the base layer I can then build up other colours (mostly greens on the upper lip, but with some pinky peach colours especially on the lower lip) in a broken pattern on top of the yellow (see WIP 6). I don't try for a particular order of pastels, despite the common recommendation to work from dark to light with soft pastels - currently I'm simply working the portrait up in sections, and I reserve those sections that are a predominantly different tone. Since all the pastels used to colour the lip are much the same tone, I don't need to worry.

Since I'm working on this painting on a flat horizontal surface, with every application of a stick of pastel, fine granules of pastel dust are produced (see WIP 6 for example). Aerosolisation of these powders is not good for one's health, so these days I pick the painting up after a short while of working on it, and tap the bottom edge of the painting on the table surface to dislodge the dust and any semi-loose flakes. I can then remove the dust from the table-top with a wet-wipe.

After adding some highlights to the lid of the mostly hidden eye with intense white pastel, it's now time to start extending the image beyond the face and head. One of the features of this frog was its gorgeous mix of colours, patterns and textures, particularly on the forelimbs. There's almost a rainbow of colours in there, transitioning from red-orange through yellow, green and cyan. I once again use a type of stippling or pointillism to add broken colour to the forearm (see WIP 7).

Frogs are always fun subjects to draw and paint because not only is their skin highly textured, they typically glisten with moisture (providing interesting highlights), and they demonstrate the most remarkable and beautiful array of colours imaginable! Colour patterns on frogs are often unique enough between individuals to be sufficient (when photographed) to identify those individuals when in the field.

Interestingly, sometimes the patterns gradually change over time - I've seen identification photos of southern corroboree frogs (Pseudophryne corroboree) that were taken over a period of years, in which the individual frog was recognisable, but here or there a yellow or black colour patch had extended a bit, or a few new spots were visible.

This alpine tree frog was raised in captivity and thus had very bright colouration and distinct skin markings. Here I've started to define one of the dark patches on the belly area (see WIP 8).

At this point I needed to block in and work up the diverse colours of the remainder of the body, so I did this with more stippling and short strokes in subdued hues (see WIP 9).

As I'm working, it helps to have my colour charts up in front of me, and the complete set of pastels within easy reach (in this case, the 525 set of Senneliers). As I choose out and use individual pastels, I leave them standing up against the wooden rim of the box so I can easily locate them again (see WIP 10). This particular painting wouldn't have been possible with Schmincke pastels, because most of the frog required bright saturated yellow-greens (which seems to have been an oversight with the Schmincke colour range).

Up until this point, my frog was floating in air - there aren't any shadows to place it in the surrounding environment, so the next thing to do is to add some shadows underneath the body.

Coming from a background of working in watercolour, where the typical recommendation is to use as few pure tube colours as possible and blend them on the palette to be used throughout the painting (particularly if you're able to create secondary and tertiary colours from the primaries), working with pastels is a completely different experience for me.

I search for the exact colour I'm after rather than trying to blend colours on the paper. Instead, I rely on regularly standing back from the painting to evaluate the tones and hues. In this case, I deliberated over the painting for a couple of days and came up with a list of things that still needed 'fixing' before I could call it finished (see WIP 11, and see if you can guess what they were!).

For starters, the loose skin under the chin was too bright, which was out of keeping with the shadows in the area. Secondly, the left hand of the frog (on the right from our perspective) had no feel of being living flesh, mainly because there was no glisten or highlights. A third point was that the tympanum (external ear) of the frog was poorly delineated (to the point of not being visible), and a little more definition in this area would make it seem more realistic (this is where an understanding of anatomy can help!). The indented line down the back of the frog was too pale, making it too overt. And finally, I didn't like the lack of textured skin above the elbow, and felt that with a little shadowing and outlining, I could make this skin seem more realistic. So I changed these things after some deliberation, and you can see the final painting in WIP 12.