Hi all.
Today i was seasoning a new De buyer carbon plus on a induction cooktop. I used grapeseed oil and I think it all went okay.
Until I was finished and the pan was bright blue on the underside(where no oil was used) i tried to scrub it away, but soap and a spunch was not enough.
The pan is still strait and not warped. But I can’t help wonder… have I harmed the pan? 
Thanks…
Søren
I think it is fine. Carbon steel can turn several colors, including blue. It is very hard to damage it. My only disclaimer is that I have used them only on gas.
Also sometimes called “blue steel”.
It’s fine.
Normal. Relax and enjoy. LOVE CS.
Thanks for your replys. I will keep using it then 
No harm. These are some pics from my De Buyer. I don’t use mine often, maybe twice a month. No idea how they ‘should’ look. I just use mine without thinking too much about it (except for not letting it out wet).
That look is the beauty of CS. Embrace the scars of use!
The beauty of a well used and seasoned carbon steel pan. But the difference is that yours looks well seasoned. Mine is blue
Just start using yours and it will become beautiful! These pans are pretty much indestructable. Mine was neglected for a few years, with rust developing, but after a good scrub i started using it again and what you see is the result after I think around 5 years of use. I bought this pan over 15 years ago!
I will.
I have used it today and so far no problems.
My concern was that maybe the blue color was a sign of overheating that could somehow weaken the steel, and make the pan more prone to warping.
I use mine on gas. From what I remember from previous discussions, it is adviseable to preheat on induction very gently, to prevent warping.
I always do. And so far no problems.
The beauty of a pan is far and away its least important feature. Ahead of it are what goes in it, how it gets cooked, how it does what the cook wants it to do, and how it holds up. A ding is not bad as long as it is not in a place or of such a size that it compromises the pan. It is honorable proof of use.
I dunno know, I think wear makes the beauty. If I come to your house and see a shiny, unscathed CS pan, I’d be thinking you don’t use it. I have my pans hanging from the ceiling, and people know what they’re eating is made with those. Look at Pedro’s pan. I’m thinking Pedro uses this thing, and not just for making pancakes.
De Buyer makes beautiful CS stuff. I’d love to own one.
Hi Soren,
what you did was simply ‘blueing’ the pan.
Many professional chefs in asian restaurants actually exert themselves to blue their carbon steel woks in the early proces of seasoning their carbon steel woks.
So it’s actually a positive to blue a carbon steel pan during the early seasoning process.
Does it actually give you a better seasoned pan ?
I doubt it, but some people swear the seasoning comes on easier and stay there for longer, if they have blued their carbon steel pans first.
Some carbon steel pans also turn pink and blue in the this blueing process.
Check this video out from School of wok where he tells you about blueing your wok without calling it blueing, but he’s blueing it as part of the seasoning process.
Link:
I have dedicated non-stick pans for eggs and pancakes, my carbon steel pans are for high heat searing and roasting. I’m lucky I bought them all on sale from the Hudson Bay Co., now just called The Bay, when they were liquidating their entire stock of De Buyer pans. A 10" an 11"(still haven’t used it) and a big 15 incher with a helper handle all for around CAD $125. Love them 
we have picked a number of perfectly good items up on our street (gentrified brooklyn over the years, including a carbon steel pan looking much like yours, a moroccan tagine with a black scorch mark on the bottom and a grill pan - I think that a certain number of folks think that their status cookware has to look pristinel Meanwhile I am happily using the same old blackened aluminum caldero I have had since the 1970s.
I like my SS pots and pans to shine a bit but not pristine , but carbon steel and CI are different animals.
Yours is completely black, but mine isn’t. Really nice.
Maybe it’s because my pan is big, it’s an oval 32 cm, so not all parts of the pan hit the high heat when I cook something in it.
I’ve tried to force it become blacker but to no avail. But it doesn’t detract from its performance: it’s completely nonstick and performs as expected.
