In the past, I have disparaged white colored pencils as being mostly useless except when burnishing, which is a fairly sophisticated technique. I questioned why white is found in nearly every colored pencil set, even those intended for kids, who are probably not going to be using it for burnishing.
At the time (more than a year ago), I forgot about the one case when a white pencil is essential: with toned paper. I first started using white (both in pencil form and in a gel pen) a few years ago with my beloved red Field Notes. And then last winter when I challenged myself with a minimal sketch kit, a white pencil became an important pairing with a tan Stillman & Birn Nova sketchbook. It has also become a key part of my life-drawing sketch kit. My favorite for that purpose is the Derwent Drawing pencil because of its exceptionally large, soft core.
Recently a colored pencil artist asked me if I had a white Derwent Lightfast pencil that I could compare with white Prismacolor and Faber-Castell Polychromos pencils – specifically for opacity on toned paper. You can imagine my delight in being of service to answer his query (requests like this help justify my rather, umm, extensive collection).
For each swatch below, I applied about three layers of pigment. Prismacolor is probably the most opaque, although Derwent Drawing, Caran d’Ache Luminance, Derwent Lightfast and Uni Pericia are all close runners-up. Polychromos is the hardest, which might account for its lower opacity with the same number of layers, but its hardness also covers the paper’s tooth more completely. (All swatch tests were done in Stillman & Birn Nova sketchbooks.)
Derwent’s Drawing pencil, purchased open stock, is a much better value than premium Luminance or Lightfast. But if you can find a vintage Prismacolor in white, it would be the best value of all – assuming that you find it in your own stash and not on eBay, where prices have gotten ridiculous for vintage Prismacolors. (Beware: contemporary Prismacolors are of dubious quality.)