bere1821 wrote:...after seriously using it for 1st time yesterday (onions, tomatoes, meat etc), i noticed some small darker spots close to the edge.
That sounds completely normal, and consistent with the three Moritaka I own/have owned.
New, the steel tends to be very reactive, as most carbon knives are. The more you use it the better, or less reactive it will become.
Cook up a few chicken breast and slicing them as thinly as possible immediately after taking them from the oven. Use the entire length of the blade. This works the best on my Moritakas' to some what force a patina (a natural patina though!).
bere1821 wrote:Also the kurouchi finish towards the edge started fading out.
Note that i VERY carefully treated the knife during prep work by cleaning it an drying it evey 5 mins.
My first Moritaka was a 170 Santoku, and the KU finish looked great, until I used an acetone rag on the blade to remove any varnish; the KU came almost entirely. My 210 Gytuo hung on to the KU a bit longer, but started wearing off when I used a soft bristled brush to clean it. It looked like a Leper, so I removed the rest and used Ferric Chloride to etch the blade, above the blade road.
So, it's fairly safe to say that at some point in the your lifetime, or the knives... it's going to look spotty, or barren of the ku finish.
Moritaka offers a finish on their knives called Migaki - polished iron clad. I may try that soon on my 210.
bere1821 wrote:Is all this normal or i shoul be worried?
It all sounds very normal.
The steel(s) will react differently with different ingredients. Potatoes turn my 20 a funky grey. Hot chicken comes out dark blue/purple.
The more the patina forms the less reactive it seems to be. They do remain a rather reactive knife though, compared to others I've used.
bere1821 wrote:Note that i VERY carefully treated the knife during prep work by cleaning it an drying it evey 5 mins.
If I may.. don't look at in terms of minutes, Look at it as "just used" or "dried".
If you cut something and have the mind set that you have X amount of time; you'll get that brown patina Luca mentioned.
If you become diligent in wiping, before setting it down to do other things, you will have far less issues.
It's also a good idea to use a micro-fiber towel for the final drying.
If you're leaving it for a while consider applying oil to it. Especially if you are coastal