Carbon steel is often used in knives to give them an unbeatable sharpness. You do however need to give them just a little extra care to keep them in top shape. There are trade offs in everything.
You will find over time that the blade changes in appearance slightly, this is call a patina. Don't worry, it's a normal property of carbon steel as it reacts to the air and the chemicals you expose it to in the food you cut.
This patina is unique to every blade and gives your knife a little character, think of it as ageing like a good leather jacket. Most of our knives are laminated knives.
These are made up like a sandwich with a stainless steel on the outside and a high carbon steel at the core which forms the cutting edge. Often these will only get a Patina along the cutting edge which can surprise some people.
Again this is totally normal however you might not find it desirable. If that is likely to be the case (and you want everything shiny all the time) then look out for knives that aren't made with high carbon edge (such as those made with VG10 or R2 steels), please be warned, it will happen.
Rust spots on your blade?
When you use your knife, make an effort to wash it straight away (not in the dishwasher!) and dry it immediately.
Don't leave it on the draining board over night or sat in a pool of water. This risks the knife going beyond a simple patina and instead starting to rust.
A little care stops the build up of little rust spots.
Rust spots on your knife are caused occasionally because it is not a stainless steel and as such they can happen but don't panic! Simply scrub them off with a brush or scratch free scourer and a little warm water and your blade will be undamaged.
Your knife will not be damaged by rust spots as long as you gently scrub them off. Avoid them in the first place by washing and drying the knife soon after use.