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I'm thinking about giving my stainless steel pot volume markings on the inner wall, like in 250ml increments, with a multitool and fine diamond tip. Various info says that scratches in stainless are benign since the material is the same throughout. Also fine scratches don't appreciably increase surface area and hence alloy release.

Yet even a fine engraving mark would be pretty micro-rough, and the first increment would be just one cm above the bottom. So there's a possibility I'd create a strong stick and burn spot.

Would you dissuade me from going ahead?

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    I'd be very careful with engraving, particularly if your pot is made of multi-ply stainless steel, where the thickness of a single ply may be less than your planned engraving depth (you have mentioned 0.5 mm in a comment) -- this could harm the pot's structural integrity and/or expose plies that are not meant to be exposed (e.g. copper or aluminium).
    – mustaccio
    Sep 18 at 19:37
  • @mustaccio You have a point. While the wall proper is just 1mm thick, the foot curve is appreciably lower on the outside than inside, so I suppose the bottom's core might skirt up there. Another reason to skip the lowest marking.
    – ariola
    Sep 18 at 20:03
  • I don't know what pot you use, but many high-end pots use laminated steel all the way up to the rim.
    – mustaccio
    Sep 18 at 21:23
  • Perhaps electrochemical etching might be better.
    – mustaccio
    Sep 18 at 22:38
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    My hand-me-down brew pot came with markings scratched into... - the accompanying big/long spoon, not the pot itself. Far less of a risk for any problems.
    – Ecnerwal
    Sep 19 at 17:55

6 Answers 6

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Go for it. Stainless steel is quite stick-friendly already, and the added unevenness from the microtool won't really make a difference. Also, this is a soup pot, and the side instead of the bottom, so you wouldn't really expect sticking.

I'd suggest that you try to make a wide marking, not just a groove, for sanitary reasons. You want water to easily come in and wash out everything, so a width of at least one milimeter would be good, two milimeters better. You can just align the bottom of the mark with the needed position, so you don't have to eyeball the middle of a wide mark.

This will be a bit difficult to do if the pot diameter is small, because your router-stick-on-thingy* is supposed to go onto a plane surface. But maybe you'll find a way to do it. In any case, really use a router bit with some width, not the side of a small cutting wheel. Ideally, the resulting mark will have an oblong cross-section, with a flat bottom, vertical sides, and a rounded connection between bottom and sides. If you don't have such a bit, make it vertical with a 90 degree angle at the bottom. The worst option would be a v-shaped groove, that would gunk up quickly, like a condo for bacteria.

And if you find it not so practical, either because of the "catches dirt" possibility or because you can't find a way to hold the bit vertically to the surface one centimeter above the pot bottom, consider acid etching instead. Chloric acid at home-improvement-store concentrations should work on domestic grade stainless steel.

* sorry, that was my best try translating Oberfräsenaufsatz into English. If you have the microtool, you know what I mean.

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    Wouldn't the corners of a rectangle be about as under-accessible as that of a V shape? Anyway none of my narrow bits is capable of forming a true corner. But you steered me from the needle to the little ball, which also moots the fact that the pot is not so large as to let a Dremel lie flat in it. Cutting depth will hardly exceed 1/2 mm.
    – ariola
    Sep 18 at 14:58
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    I'll second the acid etching idea. Grinding the steel will actually destroy the surface chromium oxide layer which is what actually resists corrosion. It will regenerate naturally even just by setting exposed to air and fairly quickly, however, when physically damaging the surface of stainless steel, you can expose iron particles in the steel to corrosion before the chromium oxide can reform. While unlikely, you may end up actually rusting your stainless steel pot if you grind the surface. Manufacturers will usually use an acid cleaning when etching stainless steel to avoid this issue.
    – CitizenRon
    Sep 18 at 22:11
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    Upvoted for the Oberfräsenaufsatz translation :-). Of course the question that comes to mind whether there is an Oberfräsenaufsatzhalter, and, in order to prevent losing it, an Oberfräsenaufsatzhaltersicherung?
    – Peter - Reinstate Monica
    Sep 19 at 8:11
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    @Peter-ReinstateMonica I'm afraid you hold the Aufsatz with your own hands, and the Germans haven't yet decided to rename them. But I've considered going fancy and mounting my Micromotfeinbohrschleifer onto the workbench, for which I could purchase a Micromotfeinbohrschleiferhalterungsschraubzwinge. The producer seems to have given up, in their catalogue they call it simply "Universalhalterung".
    – rumtscho ♦
    Sep 19 at 10:08
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    @KarlKnechtel The OP isn't talking about an actual router, but about a Dremel-style multitool that can be used for engraving, routing, drilling or sanding. In order to use it for routing, you have to add an attachment to the front of the tool that ensures that the bit will go at a constant depth into the workpiece. I just found out that Dremel calls theirs "plunge router attachment" in English, and that the German name is "Oberfräsenvorsatz" and not "Oberfräsenaufsatz" which I suppose is technically more correct, although I think the second word wouldn't strike the average German as (cont.)
    – rumtscho ♦
    Sep 19 at 21:02
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Another method is using a cold chisel as a marking punch. place a piece of wood inside the pot for use as an anvil, and then place the chisel on the outside where you want the mark directly across the side of the pan from the anvil and hit once with a medium heavy hammer. done.

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I've done this before. I didn't notice any significant sticking. I would suggest not making marks extremely low on the pot, as the lower areas get much hotter during cooking and I'd imagine carbon deposits in the scratched area would be basically impossible to remove.

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    Good to have your first-hand info! The lowest mark blackening doesn't bother me. Or is carbon deposit a glom magnet?
    – ariola
    Sep 18 at 15:01
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    The primary problem with small carbon deposits is that they'll flake off into your food. Safe but yucky.
    – Sneftel
    Sep 18 at 15:02
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In the past, on aluminium, I've engraved the outside. I found it good enough to match the water inside with the marks outside outside - this is never going to be a precision measurement. Marking the outside is easier, and allows you to engrave actual numbers as well as just marks. You can also use non-food-safe materials to fill in the markings and make them clearer (e.g. nail polish).

I did it for camping kit, when I wasn't going to carry a measuring jug but didn't want to waste water.

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As an alternative to engraving, it's possible to etch the stainless with salt, acid (5% vinegar) and an electrical source (9v battery). This really only creates a very fine surface difference, so should not present a food/bacterial trap.

  • Mix the salt and vinegar, the ratio isn't critical, just to make it conductive.
  • Attach the negative side of the battery to a cotton-swab (use a stick-swab)
  • Attach the positive side of the battery to the pot (anywhere metal is ok).
  • Mask-off the lines with tape or similar.
  • Carefully and evenly "draw" on the pot with the swab

Work in a well-ventilated space, and wash the pot well afterwards to remove any chemical by-products.

A good reference is: https://byo.com/project/etch-your-kettle-projects

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  • Extra purchases or custom soldering made etching not so attractive to me, technically best solution though it may be. But this I'll try!
    – ariola
    Sep 21 at 10:49
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Any mark is going to be a potential bacteria trap, which will be a potential problem on any pot used for water-based cooking i.e. where the temperature doesn't normally go above 100C. However this also applies to scratches from normal cleaning etc., so is probably insignificant in practical terms.

Electrochemical marking, as described at e.g. https://hackaday.com/2015/01/15/etching-steel-with-a-dc-wall-wort , will have the advantage that the surface and edges will be somewhat rounded rather than being sharp scratches, which is probably desirable in this context.

Apart from that, the warnings given about thin stainless surfaces on some other metal apply.

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  • Electro etching is the way to go. This is the method that logos are added to stainless steel knives, sissors etc.
    – D Duck
    Sep 20 at 22:03
  • One of the links in that Hackaday article specifically deals with a big stainless steel container. However I won't post the URL directly since it's on Imgur with lots of "viral videos" crap, suffice to say that it appears to do a very nice job using stick-on stencils... the ultimate original appears to be the same as in Kingsley's answer.
    – Mark Morgan Lloyd
    Sep 21 at 6:02

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