What are whetstones?

What is a whetstone?
Have you ever though what it is made of?
Modern synthetic stones come in many different types and combinations of elements. Sharpening stones share a similar composition, which includes an abrasive material and a bonding agent. The abrasive is a ceramic powder made of silicon carbide or aluminum oxide. Each compound has its characteristics, such as wear resistance, cutting speed, and hardness of the stone.
Synthetic stones have gained popularity due to their availability and low cost of production. Some believe that synthetic stones provide better results than natural stones.
Roy Underhill would probably disagree with this opinion. In his book The Wood Wright's Companion, he says that stones found in a quarry or a mine can replace modern products. Very possible that it is the case. I have no experience with natural sharpening stones yet.
I tried to explore his point of view. Natural stone seemed to me more wear-resistant and durable. No bonding agent could withstand thousands of years under the tremendous pressure underground. But also, when working with natural sharpening stones, it's hard to tell what grit they have. Synthetic stones are made from a ceramic compound that is grounded into crumbs. In this way, the crystal size of the abrasive compound is controlled during production. With natural stones, the grit is determined by the general feeling and the results after use. A natural stone must go through treatment before being used for sharpening. After quarrying, stones are leveled for subsequent use. One option is to use a similar stone and rub them against each other.
One of the things we are all facing when sharpening a whetstone – it gets out of shape. If you use a stone for a long time, it changes its shape, and instead of being perfectly flat when new, it now has all sorts of bumps and waves on the surface. Is it a bad thing? Let me explain.
Step by step we get there
Knives and scissors can be difficult to sharpen. For example, curved knives cannot be sharpened on a flat sharpening stone because of their shape. Serrated knives, on the other hand, will ruin the stone by leaving marks on a flat surface. To sharpen serrated or curved knives, it is better to use a round file or an electric sharpener.
When it comes to flat stones (but flat Earth), in my experience, the quality of your flattening tools is more important than the whetstones themselves. If your sharpening stone is deformed, it will transfer that surface to the face of the stone and make the sharpening stone unusable.

Newton told us that action always has an equal counteraction. Each movement of the knife on the stone not only sharpens the tool itself, but also changes the shape of the stone. I treat my stones after every two knives sharpened on them. Removing scratches from the surface ensures an even cutting edge across the entire blade.
If your sharpening stone is not flat, you can still use it. By changing the angle of the knife when sharpening, you will achieve results just as good as with a flat stone
Each of us uses sharpening stones in the way that is most convenient for us. At Mr. Sharp, we look for the best way to sharpen knives on whetstones for our customers. When we receive a request for sharpening on sharpening stones, we begin the process on an electric knife sharpener with a 60 grit belt. We get a new cutting edge and create a burr on it. We increase the grit to 240 grit and then move on to sharpening on the stone.

When using synthetic stones, I choose stones with 3000 to 6000 grit. Sharpening stones are used to deburr and polish the cutting edge. After finishing polishing the blade with a 6000 grit stone, I continue deburring the edge on a leather strop.

It is more about your style that you find attractive. It all comes with experience, just like everything else.