"Instant antique for stainless-steel warriors!"

[Matt Lukes]

Indeed a white vinegar (5% acetic acid v/v)/ table salt solution is a very effective way of 'aging' steel- you just have to be careful not to overdo it is all. You can stain a blade in just few seconds if you want that kind of look or you can submerge it for a time to get the results as shown on that website. Now those are intended to look antique- not just to address the silly shininess of stainless steel, so most of us wouldn't go anywhere near the introduction of pits or anything. Real swords would have likely been cleaned constantly to combat corrosion, but certainly not to a mirror finish, so should look so- treat your stainless steel blade with the solution for a short time and then 'polish' it with a Scotchbrite pad or other such very minor plastic abrasive, and it'll look nice and 'in use'. The acid will leave some very light grayish staining, the polishing will dull that some and leave some microscopic scratching that will dull the overall finish and voila- a gladius that was just yesterday conquering the local barbarians

Just as an illustration, I once dumped a bunch of chromed steel nuts into a container of white vinegar- barely 5 minutes later they were a nice deep gray... so acid, even weak acid, can have a marked effect on metal faster than you might think. Always keep an eye on whatever you're treating until you know how it'll behave.

One thing- any residue of the vinegar and salt solution will concentrate as the water evaporates, so it's important to rinse your blade REALLY REALLY well after treatment, and dry it well too.

I did all this to mine and I really like how it looks.

Matt