What did Mondrian change? In all but three cases he added blocks and bars of primary color and occasionally black. These elements are easy to notice, for they seem to float and slide within the structure of black lines. He also reworked the black lines: new lines were added, old ones were extended, narrowed or widened, and often their positions were shifted. Existing color fields and white areas were repainted as well, often more thickly, showing more impasto. But Mondrian's color additions were the real revolution: for the first time, he released his rectangles from the black lines and canvas edges bounding them on all sides and allowed them to touch the white spaces of the composition, to breathe. When the dealer Sidney Janis asked him about these radical new elements, Mondrian said they gave the paintings "more boogie-woogie," referring to his great new musical enthusiasm.