Diego Velázquez ranks among the greatest masters of seventeenth-century Europe. By 1623, the twenty-four-year-old artist was established as court painter to Philip IV in Madrid. For nearly forty years, he was primarily occupied with painting remarkably innovative portraits of the monarch and the royal family. But in his spare hours, Velázquez turned to subjects that interested him personally; The Needlewoman is among those works.
His observation of the optical effects of light on the forms he painted caused Velázquez to abandon the tenebrism -- or extreme contrast of lights and darks -- that characterized his earlier works in favor of a softer style. Here, no area is obscured by darkness. The artist used a gentle light and deep, but translucent, shadow to reveal each plane of the face, to sculpt the swelling bosom, and to suggest the repetitive motion of the hand.
Because the painting remains unfinished, the steps in the artist's process are visible. He began by priming the canvas with a gray-green base. Next, he indicated the main forms of the composition, sketching them in with darker paint, then brushing them in with broad areas of opaque color, and finally, building up the face -- the only area that appears to be finished -- with transparent layers of glaze, giving it the effect of flesh seen through softly diffused light.
More information on this painting can be found in the Gallery publication Spanish Paintings of the Fifteenth through Nineteenth Centuries, which is available as a free PDF https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/spanish-painting-15th-19th-centuries.pdf