Very, very, very thin paints applied in many, many coats, by someone who appears to have background as an illustrator.
The highlights were painting by applying very smooth, thin coats. In my opinion, by one of the greatest miniature painters there ever was, who has excellent technical skill along with a great sense of personal style and an obvious fine arts background.
What makes rackham miniatures look so different is the different style. For one, highlights aren\'t always brought up to white, and not just applied to raised detail. They are added with an artist\'s knowledge of how light falls on an object. In the most commonly seen style - games workshop - highlights are applied to create contrast.
For example, imagine a piece of cloth laid over a chair. There are may horizontal folds in the cloth. Light falls on the cloth from the top and slightly from the left. Let\'s examine how the two painters would approach this:
GW: Highlights would be applied to the highest areas, slowly blended to shadow in the recesses. See image 5401 for an example, look at the red jacket. This makes the folds pop out and look attractive.
Rackham Painter: Highlights would be applied to the tops of each fold, so that at the highest point of the fold there is a transition between light and dark. This is the way the fabric would actually appear. This looks more realistic, and even with the cartoony style of Rackham, looks better because it rings truer.
here is a bad bit of art I knocked up in windows paint because my Adobe Photoshop isn\'t working right now. The first from the left is GW style. This is the style I\'ve been using for all my years painting, but am trying to move away from. Second from the left is the way Rackham is highlighting. The one on the right is an example with a rounded surface. The more the surface faces the light the lighter it is. So, where the fabric bends through the verticle it is in transition from light to shade, and is a mid-tone.
The best resource for this style of painting is in the Euro Modelissimo line of books.