Uncoated plastics and elastomers can be routinely examined, as can uncoated biological samples. Zinc coated steel replaced the previous uncoated rust-prone sheet metal. Tracing paper may be uncoated or coated. Coated or uncoated papers may have their surfaces polished by calendering. The resulting coated steel can be used in much the same way as uncoated. Porous materials like uncoated concrete tubes cannot be used. The material improves wet adhesion 15-fold compared with uncoated pillar arrays. Natural tracing paper for laser printing is usually uncoated. This forces the liquid resin into all crevices, eliminating uncoated surfaces in interior cavities. Domtar operates the Kingsport Mill at which the company produces uncoated freesheet. Uncoated tips brazed to their shanks were the first form. On uncoated parchment (and paper), silverpoint is particularly light in value. Technically it is called "lightweight offset paper" and is a type of woodfree uncoated paper. Uncoated fabrics provide the next level of heat insulation and light absorption. It also elicits much lower immune response than the uncoated particles.