Polyurethane is essentially a plastic that is liquid until it cures, is available in both water and oil-based versions, and comes in several finishes ranging from satin to glossy. Because of its low toxicity and minimal odor, water-based polyurethane is popular. It goes on clear and dries considerably faster than oil-based alternatives, plus it doesn't add any color. Water-based polyurethane is susceptible to heat and chemicals. It's ideal for bookcases, desktops, and picture frames that won't be subjected to high temperatures. Oil-based polyurethane is more durable than water-based polyurethane, especially when it comes to heat resistance, therefore it's a smart choice for a kitchen table. Although polyurethane is frequently confused with being different then wood sealer, it is actually a form of sealer.