(hint #1) Being able to play whatever I want has been a central theme to my own discovering how to play guitar. I've been on that path for 37 years, and it's enabled me to uncover, test and refine a unique, skill generating learning approach.
It is important to note that urethane foam is most commonly used to refer to a material made from polyurethane. The urethane reference in this name is to the type of links, also known as carbamates, that join the units in polyurethane.
What is the difference between polyurethanes and urethanes? Polyurethane coatings were invented in the mid-20th century. Plastic resins in liquid form, they are used primarily to protect wood surfaces. Their main ingredients include acids derived from vegetable oil, nitrogen-based chemical amalgams, isocyanates, and mineral spirits.