Which item is NOT considered a porous surface?

Tile is not considered a porous surface because it is typically made from materials such as ceramic or porcelain, which have been fired at high temperatures to create a dense structure. This process causes the surface of tile to be non-absorbent, meaning it does not allow liquids or gases to easily penetrate it. In contrast, porous surfaces like paper, wood, and fabric have interstices or spaces that can absorb moisture and other materials, making them susceptible to staining and degradation over time. Understanding the properties of different surfaces is critical in forensics, as it influences how evidence is collected, preserved, and analyzed.