The "Flemish Style" is really a technique perfected by the masters during the Renaissance primarily in the areas around Flanders. The technique employs seven layers to achieve the detail and color clarity Dutch Master works are famous for. The layers start withan under drawing followed with a glaze of Umber. After the Umber glaze more Umber is added to make a tonal study. Details are added during the creation of a gray layer and refined with the addition of the initial color layer. The final layer are the finish details and lastly the varnish.
Rembrandt and Paul Rubens are just two of the more well known painters who pioneered this technique. The primary reason for such a labor intensive study is that this style ages much more slowly than other types of oil paintings. Many 20th century works are in relatively poor condition when compared to 400 year old.