When buying brand new stainless steel kitchenware (e.g. pot, pans) I found out there is this black residue that is not visible to the naked. Nowadays I always do 2 different checks before buying any stainless steel ware e.g. wok, bowl, plate, kettle, spoon, water bottle, lunch box, etc.
1) First check, wipe the stainless steel ware's surface with a white tissue paper, and check if you can see any black residue on the tissue. The photo below shows a stainless steel lunch box purchased from Lazada, from a China seller that has no ratings. Just one hard wipe on its seemingly shiny surface, and the black residue can be seen on the tissue.
2) Second check, wipe the stainless steel ware's edges, especially if it has "folded edges" (the photo below shows the Ikea's Blanda Blank bowl). The "folded edges' is highlighted with the green arrow, the black residue is highlighted in the green circle. Now, if I see any black residue from the "folded edges", I may or may not buy this item, depending on - will the food come into contact with the folded edge at any stage of food preparation?
A closer look at the black residue
I was surprised that for many years, Google search returned
only 1 result when you enter the term "stainless steel has black residue". Maybe nobody thought it was a big deal, maybe nobody noticed. Some online users suggested it is "carbon residual", "chromium rust", "polishing oil", but there is no way to tell for sure without sending it to a lab (I can't afford this).
Using the Endo stainless steel "Apple" Bento box (see photo below) as an example to take a closer look. The "bowl" and "cover" passed the 1st check, the "plate insert" did not, I tried to clean the plate's edges, because it does comes into contact with food - when I put hot food into the bowl, the steam would raise up, get trapped at, and condensed at the plate insert's edges, this condensed water will touch the black residue & flow back into the hot food - was my logic.
I poured and soaked the plate in boiling water for 10 minutes. You can see the black residue starting to come off in tiny bits, highlighted by the green circles.
I also used a toothpick to scrap into the folded edges, took the plate out of the boiling water, wipe it with a tissue - and the black residue is still there.
I used my fingers to pick up some of the black residue, then rub it. It smudges and felt like oil. Maybe it's harmless in the short term, but there is no way for us to know without lab testing. And I'm not sure manufacturers really care about people's health, e.g. Subway has been adding Azodicarbonamide into their bread for years, until consumers bring it to attention.
In the end I still use the Endo Bento box, but without the "plate insert".
How to get rid of stainless steel black residue
I did not find a effective way. I have tried washing with dish washing liquid more than once, scrubbing it with a sponge, pouring boiling water over it, nothing cleans it up completely, one tissue wipe later and it will show up again. Based on my own experience, even stainless steel ware from big name companies fails this simple tissue wipe test.
Some online users has suggest using "Bar Keepers Friend" a type of powder metal polish, some suggested boiling vinegar and water, it worked for some folks but not the others, because everyone has stainless steel wares from different manufacturers, who may use different materials. Since I now "wipe before I buy", I did not get to test out these 2 suggestions.
List of stainless steel wares that passed at least the 1st wipe test
These are items I have either purchased for my own use, or I gave it a wipe while shopping at the departmental store (but did not buy as some are too expensive). Maybe it's useful if you intend to buy them online, given the lockdown / circuit breaker closed most departmental stores. Do note manufacturing practices may change (cut cost, outsourcing), so this list may not be 100% accurate.
- Zebra 14 cm Mug with Lid
- Zebra Whistle Kettle Prima 2.5L
- Zebra Smart Whistling Kettle 3.5L
- Zebra oval lunch box 16cm
- WMF Select it! 30cm Wok with glass lid
- WMF Herb/ Tea Infuser ball
- Takahi Energy-Saving Thermal Cooker with Warmer 22.L+0.8L
- Philips Viva Collection Kettle 1.7L with Keep Warm Function HD9316
- Endo "Apple" Bento Lunch Box
- Fox Run Stainless Steel Popsicle Mold, Set of 6, Silver (from Amazon)
- AiYoo Three Sections Round Divided Dinner Plate Set of 2 (from Amazon)
- 3 level dish rack, with 3 trays (from Ezbuy), the translation is not very good - 304 bowl rack drain rack drying set table dishes, dish tray supplies storage box kitchen shelf 3 floor
All reviews are true, I'm not affiliated with any any entity, nor get payment in any shape or form, indirectly/ directly.
