(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.
Urea is a raw material used in the manufacture of many chemicals, such as various plastics, urea-formaldehyde resins and adhesives. It is also essential for making feedstock, glue, fertilizer, commercial products, and in resin production.