HOW TO FLATTEN A WHETSTONE
Step 1. Flatness measurement
Measure the surface flatness by eye or use a straight edge. A ruler or engineer square may be an option. This determines the grade of sharpening the stone’s concaveness. Lay it down on the surface and see if there is a gap between the edge and the stone.
Step 2. Soaking
Soak the whetstone for 5-10 minutes until bubbles have disappeared.
Step 3. Marking
Draw a pencil grid to see the progress.
Step 4. Breaking the diamond (with a new plate only)
The surface of a new plate may have high spots or larger diamond particles. So, use a diamond breaker for 2 minutes to remove and slightly break them. This will protect the whetstones from scratches.
Step 5. Flattening
Rub the stone over the lapping plate under running tap water with straight movements. If running water is not an option, make sure your whetstone is sufficiently wet.
Keep an eye on pencil marks. Once they're gone, you are done. To prevent cross-contamination, rinse the plate thoroughly before moving to another stone.
CAUTION: If you have natural stone, be aware. It’s relatively harder, and plate wears off quicker. Use a sanding belt cleaner to avoid plate clogging.
Use the Lapping plate only with whetstones (i.e., water as a lubricant for sharpening) or only with oil stones (i.e., honing oil as a lubricant for sharpening). Dedicate it to one of these types because oil may transfer onto waterstone.
Step 6. Drying and Storage
Wash the plate carefully and dry it after usage.