Working with Pigments – A Basic Primer

Artist’s pigments have been around for centuries, but have been used on scale models for only the last 25 years or so. Prior to that, artist’s chalk pastels were the hobby standard.

Artist’s pigments are basically finely-ground dirt, chemically leached from a variety of clay and oxide compounds. Because of the nature of artist’s pigments, they lend themselves perfectly to weathering scale models.

Pigments can simulate a wide variety of naturally-occurring environmental effects. Rust, water stains, and dirt and dust are the most common. In this primer, we’ll discuss the various techniques that are applied to achieve these effects.

Balance of Tones and Base Color
Natural weathering occurs over time, and under a wide variety of environmental conditions. A dry, windy day will leave a coat of dust, then rain in the evening streaks that dust down the side of the vehicle. The next day, it’s hot and sunny, and that bleaches the rain streaks and makes them prominent. To achieve this effect on a model, you have to replicate each part of the natural process in layers.

The colors you select in your weathering process play a vital role, along with the base color of the model you’re weathering. A light dust color, for example, will have far more contrast on Panzer Gray, than it will on German Dark Yellow. In contrast, a dark earth tone will stand out more on a lighter surface. The key is finding the balance between the pigments you select and the base color of the model. Factor in, too, the environment that your model ‘exists’ in. You won’t see red Russian soil in the tracks of an Afrika Korps Panzer III.

 Color alterations
An unweathered, base-coated model appears very flat, with little or no contrast. Add some subtle changes to the overall tonality of the model with pigments. A like color, such as a light green over a dark green, can effectively change the reflectance and tone of a panel, turret side, etc. A simple dab in the middle of the panel, followed by a circular motion with a soft brush, will lighten the center of the area and create that ‘less than perfect’ single color.

Many modelers pre-shade and post-shade their work to create artificial contrast. Pre-shading and post-shading both require practice, an airbrush, and patience. If your base coat is too heavy, there’s goes your pre-shading. If your post shading is too stark, it makes the model appear cartoonish.

Pigments can easily replicate pre-shading and post-shading, are much simpler to apply, and are reversible if you follow a few simple steps.

Paint your model in the overall base color.
Apply a darker pigment color (relative to the base color) along the edges. This will replicate the pre-shading process.
Apply a lighter pigment color (relative to the base color) to the center of the panel or area. Blend outwards.
Flat-coat the model.
Flat coating the model will tend to lessen the effect of the pigments. This happens for several reasons.

Air pressure too high during application – removes pigments from surface.
Too much clear coat lifts the pigments, suspending it within the clear coat.
Initial application of pigments is too light. The added light diffusion caused by the clear coat further reduces the effects of the pigments.
These three factors can be easily avoided. Use light, low-pressure coats of clear flat, or apply the pigments heavier than you normally would to compensate. I personally prefer the latter. In some cases, especially with models that are mounted on a base, I simply apply the pigments over an already flat-coated model.

Dry Techniques
By far the easiest and most common method of weathering with pigments is the dry method. A dusting of pigments applied over the top of the base coat. The advantages are many – precise control of where the pigments go and their intensity, a wide array of weathering effects, and most importantly, a quick method of weathering your models.

Dry techniques also have some disadvantages, including loss of effect with clear coat, unrealistic effects due to over-application, and susceptibility to blemishes resulting from handling.

Wet Techniques
Wet techniques offer additional choices to dry weathering. The decision to use a wet technique should be based entirely on what effect you’re trying to achieve. The standard rule I use is simple – if the effect was caused by rain water, I use a wet technique.

Wet techniques also work exceptionally well for caked-on mud, although the carrier I use changes from Turpenoid to artist’s acrylic gel medium.

Application
I use Turpenoid brand odorless thinner for wet techniques. Because the overwhelming majority of my work is done with acrylics, Turpenoid is my preferred carrier since doesn’t affect the underlying paint.

Rust and exhaust: Determine in your head how long you want the rust or exhaust streak to be. For the sake of demonstration, let’s say 1 inch.

Using a clean brush, apply a small amount of clean Turpenoid to the starting point of the streak. This can be a bolt or rivet on armor and aircraft, or a hawsepipe or limber hole on a ship.

Using the same brush, apply a small dab of pigment to the starting point of the streak. The amount of pigment you add determines the intensity of the streak.

Using a dry, flat brush, pull the pigment downward with a flicking motion. Wipe the brush on a dry cloth or paper towel, then lightly work the pigment back towards the start of the streak. This will maintain the length of the streak and keep the edges from too soft.

This works effectively with red-colored pigments for new rust, darker oxide colors and earth tones for old rust, black for soot and gun barrel residue, and gray/brown for engine exhaust.

Water Stains: The hardest effect to achieve with pigments are the effects of water staining. This is because water staining is almost an overall coverage effect, instead of a localized effect like a rust streak. Water stains can be achieved effectively with the use of oil paints, but oils are often a one-shot, don’t mess it up affair. Rain streaks are applied in a similar manner to rust streaks, although the colors are very different. The color you select depends on the base color of the model. A Panzer Gray model would be best suited to a light gray or even white application of pigment, whereas an Olive Drab tank would benefit from a light or natural yellow mixed with white or light gray. Since rain streaks are usually extremely thin layers of residue on a real subject, replicating it on a model simply means that you need to slightly alter the base color of the model itself. It doesn’t mean you have to apply an opaque layer of pigment.

To apply a water stain over a large area, along the edge of a turret roof/side for example, simply apply a clear Turpenoid stripe to the top of the vertical surface, then lightly paint a thin line of pigment at the top of that stripe. Using a wide, flat brush, pull the pigment down through the Turpenoid stripe into the base paint. This technique does require practice, not so much for the technique itself, but rather, achieving consistency along the entire length of the area being streaked.

Mud

Mud ends up everywhere…whether its on the treads of a tank, the landing gear of an aircraft operating from a forward base, on a rally car, or on the boots of a infantryman. Because pigments are best suited to tonal changes of the base color, you’d think they wouldn’t work well with heavy applications of wet mud, but they do.

The key to mud is acrylic gel medium. It comes a variety of consistencies, and is available in flat, gloss, and semi-gloss varieties, although this isn’t overly important for what we’re using it for. Gel medium is used by artists to thicken acrylic paints, to give them the consistency of oil paint, without the long drying times.

To achieve caked-on mud, you’ll need gel medium, a decent amount of pigment, and several disposable brushes. If you’re really going crazy with mud, having some acrylic paint that’s close to your desired ‘mud color’ isn’t a bad idea, either.

Start by mixing the pigment with the gel medium. It will turn very dark as you mix it, but I assure you, once it dries, it will return to its original color. Apply the mix to the model as you desire. If you want smooth, watered-down mud, smooth it and allow it to settle. If you want gritty, chunky mud, wait for a few minutes then stipple the mix with an old brush. They key to the mud is to allow it to dry. If you’re not happy with the application, you can simply apply more mud over the top. After the mud has dried, a wet application of mud with Turpenoid can provide you with a nice transition from dusted paint to completely mud-covered. To blend it all together, a dry application of your base color will complete the process.

If you want wet mud…do a wet application over the dried gel medium using a darker color than the base. Follow that with an application of clear gloss onto those areas that you want reflection. This will simulate still-wet mud.

Summary
The key to effective weathering with pigments is experimentation. I cannot stress the importance of looking at everyday pieces of equipment in our lives – farm implements, construction equipment, etc. The tracks of a bulldozer at a building site will collect mud the same way a Tiger tank will. The silver paint on your car will streak rain the same exact way a natural metal P-51 will. Rain streaks on the sides of buildings, bridges, rail cars, etc., are all perfect examples of the countless effects you can achieve with pigments.

(Disclaimer: These are the techniques I use. Do not use these techniques on a brand-new, 1000-hour build model and expect perfect results. Experiment on old models, pieces of painted styrene, etc., until you’re confident with your individual results. They work for me, but I’ve also been using these techniques for years, and I’ve had lots of practice. And no…I’m not going to replace that model kit that you messed up using one of my techniques!!)