DUO whetstone on bamboo Thanks to its special properties, this whetstone sharpens kitchen knives particularly efficiently. Firstly, because it has two different sides. The blue side (240 grit) is used to restore blunt or damaged knives and the fine, white side with 1000 grit restores the perfect edge. Place in lukewarm water for 5 minutes before use. In combination with water, the smallest corundum particles form an abrasive paste, achieving exceptional sharpening results. Richardson Sheffield - knife expertise. The traditional British brand has been recognised as one of the world's leading knife manufacturers since 1839. The quality of the brand convinces both passionate hobby chefs and professional chefs. Thanks to state-of-the-art technologies and many years of experience, the brand develops high-quality collections that combine performance, functionality and design at the highest level.