The ESP Guitar Company

"polyurethane" is a class of polymer, not a specific formulation, and there are myriad different ways of mixing a polyurethane clear coat. some will yellow, some won't. moreover, some people (but generally not manufacturers) will apply the "polyurethane" label to any synthetic polymer clear coat, when in fact there are other types, like polyester, acrylic, etc. which are not readily distinguishable to the average consumer, but do have different properties. people who blindly say "poly doesn't yellow" are simply misinformed and overgeneralizing.