How do glazes and impastos create different effects in oil painting?

In oil painting, glazes and impastos are distinct techniques used to manipulate light, texture, and color depth.

Glazes
A glaze is a transparent wash of pigment thinned with media such as stand oil or oleoresin. Because they are translucent, glazes allow light to pass through the paint layer and reflect off the ground beneath. This technique is primarily used to:1
* Achieve greater depth of color and subtle tonal transitions.1
* Create deep, glowing shadows.1
* Bring contrasting colors into closer harmony by applying a unifying tinted film.1

Impastos
Impasto involves applying paint thickly to a canvas or panel so that it stands out from the surface, creating a ridged, three-dimensional texture. This technique is used to:23
* Mimic the broken-textured quality of highlights, such as the sparkle of jewelry, armor, or the texture of wrinkled skin.2
* Define forms through physical, gestural application, as seen in the works of artists like Vincent van Gogh.23
* Emphasize the physical, material qualities of the paint itself, a common goal in modern abstract painting.2

While glazes rely on transparency and layering to modulate light, impastos rely on physical thickness to catch light and create tactile interest.21