Rated 5 out of 5 by VT Sign guy from Not very water soluble I have yet to find a surface that these pencils will not create an adequate reference mark on. However, I have found the claim that they are "water soluble" to be a stretch at best. I have found the best way to somewhat erase these marks is with a combined dishsoap/water solution paired with extremely vigorous scrubbing with a squeegee that has a fresh felt pad. 100% mark removal is next to impossible, so definitely don't use these on any viewer-facing surfaces. Get stabilo pencils if you want true water solubility.