we make lots of purchases from this site,but i have to say that the guitar set may be my personal favorite!! pressure rollers are made of special tool steel that ensures uniform pressure application. i love the bold colors that are perfect for the spring and the welcoming smile on his face. the funny thing about having forty-four kids in a school is that everything happens quickly. as i read and understand the directions i believe i am being told to add water to acid and not acid to water. 