Before getting upset, check whether the polyurethane has actually dried. If you're using water-based material, it's common for it to appear milky before it dries. The color comes from the emulsion that carries the resins. If the finish is still wet, just wait -- the milkiness should disappear.

Why is my polyurethane white?

White spots on polyurethane are generally caused by two things: Not stirring thoroughly enough before applying it, or a buildup of moisture. While preventing the white spots is easier than fixing them, you can fix them by sanding down the high spots and then drawing out the moisture.

Is polyurethane supposed to be clear?

Water-based polyurethane is clear, low-odor and has a quick drying time. It is recommended for surfaces that see little exposure to heat or the elements, such as desks, bookcases and end tables. It may require more coats than oil-based.