Glass makes a solid surface to absorb the markings that might harm the wood. It will scratch, but it is impervious to water and most household liquids and cleaners. Since glass is hard to handle in large sections, this type of covering is probably better for small tables no wider than 3 to 4 feet. Since the glass will have the support of the wood, the thickness can range around 3/8 inch for a safe and solid surface.
Plastic tablecloths are the cheapest solution for covering wood tables. Most manufacturers make the plastic covers in bright cheery colors to mimic cloth. In addition, they glue a soft lining on the underside so that the covering slides over the wood softly, further protecting the wood surface. Plastic tablecloths tend to rip and stain over time, but they work well for a temporary measure.
Matting is a custom-designed combination of plastic and cardboard about 3/8 inch thick. Although it is often designed to look like wood, you normally use it in combination with a cloth tablecloth. This barrier keeps moisture, heat and pressure from harming the wood surface.
Wool blankets make excellent protective coverings for wood surfaces. The fibers are very resilient and moisture-absorbing while also fire-resistant. A thick wool blanket makes a soft base for table wear, reducing noise at the dinner table while adding an aesthetically pleasing look to the room. Smaller wool blankets add charm to living room coffee tables or bedroom side tables.