Poor quality whetstones have many disadvantages. One of them often seems to be that they only remove heavy metal from a blade. If you grind several kitchen knives in a row on it, you should not use your finger as a spacer to the stone to maintain the angle. The stone is wet and cold, you won't notice if your finger is also being "sharpened" and at some point you'll just wonder what brown-reddish streaks suddenly appear to be coming out of the water stone. 🙄