The Use of the gum arabic creates a soft pastel that can also be wetted once on the substrate, and spread like a Watercolor. Their vibrancy and brightness can attributed to not containing clays, like other brands. Sennelier has a rich history of providing Plein Air Painters like Cezanne with their pastels, giving him the ability to produce the vibrant, rich landscape works he is known for. This 80 Color half stick Plein Air collection has been carefully selected for its’ simplicity and ability to mix a full spectrum of landscape Color, without carrying the extra Weight of too many pastels in the field. Half sticks are great for making broad strokes, to cover larger areas more quickly. Senn sp 80 lscpe 1/2stk set