First and Foremost is the Steel
Plain Carbon Steels: These steels are inexpensive, easy to work. They quickly rust and pit, and they frequently dull.
Stainless Steel: These steels are highly stain and rust resistance. It is easy to sharpen but wont take or hold a edge very well.
High Carbon Steel: These steels allow a blade to stay sharp longer and hold up much better under abuse. But it is not as stain resistant as Stainless Steel.
High Carbon No Stain Steel: A higher grade of steel, it has the best attributes of each, and a harder more stain resistant blade. The very best comes from an area of Germany called Solingen.
Method: How the Knife is Made
Stamped Knives are punched out of a thin sheet of metal, then tempered, sharpened, and then finished by machine. The blade is then attached to the handle. It results in a lighter, narrower blade. They are easier to produce and less expensive. Stamped blades can be identified by the absence of a bolster.
Forged Knives: A forged knife is one that has been made out of a solid steel bar heated in a furnace to a very high temperature, then set into a mold and hammered to produce the blade. The knife is then tempered, ground, polished, and assembled, mostly by hand, into the knife itself. The knife will always have a bolster and an integrated tang.
Tang Didn’t Just Get Us to the Moon!
A Full Tang: All quality knives have a full tang. Generally, a full tang is considered to be the most secure method of attaching a handle to a knife and is recommended for knives that will be used for many years, even generations. The long tang gives the handle a better connection to the blade and the knife will feel a little easier to control because of this connection and the balanced feel.
Encapsulated Tangs: These are plastic handles molded onto a tang. These are very inexpensive to manufacture and can separate.
Half Tang: These knives have a tang that only extends about halfway down the handle. These tangs are generally too short for knives that are used constantly or with a decent amount of force. These knives should be avoided.
Wood Handles must be cleaned thoroughly. They will crack splinter, break or warp and can harbor microorganisms. Wood handles are not allowed in the kitchens of most restaurants.
Plastic Handles are easily cared for. They may become brittle over time, resulting in cracking and chipping. The material is light, the result is a knife that is off-balance or too light.
Composite Knife handles are made from hardwoods infused with resin, called Pakkawood. It is very dense, tough and is pretty much waterproof. They are considered by many chefs to be the best choice because they are as easy to care for and as sanitary as plastic.
Metal Handles are the most durable of all handles, as well as the most sanitary. However, they are very slippery in the hand, especially when wet. Another disadvantage of all-metal handles is a question of balance.
The Cutting Edge
Serrated: Serrations are often used to improve the cutting ability of a less-expensive blade not capable of taking and keeping a sharp edge. The points protect some of the cutting surface but the point dulls rapidly. Then you are not cutting, you are tearing or sawing through things. Then, once it is dull you cannot sharpen it yourself.
Straight: Straight edges make the cleanest cut through foods and are used for slicing, dicing, chopping, pealing and paring. No chef in the world uses a serrated blade on anything but bread.
Some Notes on the Edge
There are two schools of knife sharpening – those who like a knife to keep some roughness from the stone and those who believe that it should be as smooth as possible. Both approaches have their benefits.
Blades with a rough edge can be aggressive cutters, especially when the blade is thin. They have micro-serrations that act like a microscopic saw. These micro-saws are very well suited for slicing fibrous material, such as a rope. Sadly for those who are supporters of the keep roughness school of thought there is very little need for cutting rope in the kitchen. This edge is easy to produce because you just stop sharpening after a medium stone (200 to 300 grit). Blades sharpened this way do become dull faster as the points wear or bend, so frequent touch-ups are needed.
Smooth edges are best for cutting with a straight push and are preferred by barbers, surgeons, chefs and woodworkers. Research done by John Juranitch shows that butchers can cut more meat per shift and tire less when using a smooth edge. Analysis with an electron microscope has confirmed that wood cutting ability is correlated to edge smoothness. Sharpening a smooth edge requires more work, but the results are worth it. So lets put this debate to bed and lets just go for the smooth as possible edge.