I`ve used them for decades, some colors have a higher wax content than others and there are a few levels of quality in the pencils. Layering works nicely until at some point, with the ones I use, they just won`t layer any more, I get kind of ugly, waxy blobs. I also use kneaded erasers a lot some of which leave a film on the paper which shows up when I apply the colors or shading. I have recently discovered a series of Mitsubishi coloring pencils of very good quality...I`ve used their top end pencils for a long time so I decided to try their colors and like them very much.