The antonyms of "most close-grained" include open, coarse, rough, porous, and grainy. These words are used to describe materials that are not tightly packed, have visible pores or gaps, or have a visibly rough or uneven surface. Open materials allow air, water, and other substances to pass through them easily, and they tend to be less dense than close-grained substances. Coarse materials have larger grain sizes and are less smooth to the touch than close-grained materials. Rough materials are uneven and can be difficult to work with, while porous materials can absorb liquids and gases. Grainy materials have a noticeable texture and do not feel uniform to the touch.