Seasoning carbon steel -- Canter method turned plan bright blue
I just got a de Buyer Carbone Plus plan and, after doing a bit of research, decided to try the Canter method of using flaxseed oil and baking the pan in the oven. The first coat seemed to go ok, so I re-oiled the pan per instructions, wiped it off, etc., then put the pan in for a second round. This time, however, the pan has a bright blue oily sheen covering much of the pan. The blue coloring does not cover the entire pan, mind you -- the top part of the sides, near the rim, is normally-colored.
Any thoughts (a) on what might have happened and/or (b) what I should do about it? I am inclined to steel wool the pan back to bare metal (or at least try to do so), but should I? Is the blue coloring harmful, or just some artefact of the oil baking out of the pan?
Appreciate any help you can offer...
For the sake of correctness:
The blue coloration has to do with a thin layer of metal oxide which has formed on your cookware. The color attained by the steel is a reliable indicator of the temperature the steel reached as well as the thickness of the oxide layer. This fact has been used for centuries in the process of quenching and tempering steel (in order to manipulate the steel's hardness and durability).
It's worth noting that the oxide layer can grow in thickness (and change in color) depending on other conditions (length of time, presence of certain gases), but that it's a mostly good thing. The oxide layer passivates the surface, preventing rust formation. Also, in terms of seasoning a pan, it seems that formation of a black oxide layer (Fe3O4, aka magnetite) may play a key role. Black oxide is a conventional conversion coating process used on steel parts (for example: "dry wall screws"), partly because it's an inexpensive way to prevent corrosion- and part of that is that it will take up waxes and oils. For a seasoned carbon steel pan, this means that the oxide layer may be the reason why the seasoning sticks to the pan at all.
Anyways, your pan turning blue, and what that means (the formation of an oxide layer), is more than normal, it's a necessary part of the seasoning process.
I don't think you need to scrub it off or start over. The blue color is actually from the metal. Carbon steel can and will turn different colors depending on the mineral content so it's just likely that you had one that had a bit more of the minerals that become more prominent through the heating/seasoning process. It doesn't change anything about the pan, and over time as you season more, the pan will darken just like others.
I suspect though cannot prove one of the reasons deBuyer recommended using potato peels in seasoning is that in addition to helping remove the protective/non-rusting layer applied to all cookware during manufacturing, boiling potatoes helps darken the pans.
I've seasoned several carbon steel and cast iron pans and found that the ones with the blue color will turn black through proper use and maintenance just like the others.
I have also found that seasoning on a stovetop tends to give more control. I just seasoned a carbon steel pan last night that turned from very blue to just some blue through the muti-step seasoning process - not quite the exact Canter method.
Basically it's: 1) Wash with hot water, soap, and plastic scrubbing pad two times, then rinse with hot water; 2) briskly boil peeled potato skins or quartered potatoes for 20-30 mins, dump potatoes, rinse off buildup and repeat with second set of pototoes/peels; 3) rinse thoroughly with hot water only and non-abrasive sponge; 4) dry on stove using heat - not a towel or paper towel - want to keep the surface as free of impurities as possible; 5) mist with canola oil and wipe the interior and exterior using silicon mitts or tongs so you don't burn your hand - you're trying to leave a super thin layer - as thin as the wipe you'd do just prior to putting away for storage; 6) heat on high heat for 5-7 mins depending on the thickness of your pan and the BTUs of your burner (it helps to have one that's at least 15k BTU); 7) let cool for 20 mins; 8) repeat steps 5-7 for a total of 3 times. That should leave you with a well-seasoned, dark pan that's ready for use. It will still darken over time, but this works well with the blue pans, especially when the blue looks shockingly blue like a few of mine have.
Thanks for the very detailed reply. I was a bit concerned about cooking on a pan covered in a rather poisonous-looking shade of blue, so it is more than helpful to know it's just a feature of the pan itself. I actually looked all over the web before posting this message and the only reference to the problem I found was a complaint by someone else.