What artistic effect does the plique-a-jour technique primarily create?

The plique-a-jour technique primarily creates a see-through, stained glass effect, which is characterized by transparent or semi-transparent enamel over an open framework. This method allows light to pass through the enamel, giving the appearance of stained glass when viewed against a light source. The result is a vibrant play of color and illumination, as the enamel mimics the qualities of glass. This technique is commonly used in jewelry and decorative arts to enhance the aesthetic appeal and to create intricate, colorful designs that showcase the craftsmanship involved.

The other options do not convey the significance of this technique accurately, as plique-a-jour is specifically noted for its transparency and light-transmitting quality rather than a solid color finish, metallic sheen, or textured surface.