Apologies if similar thread was opened in past, but it seems I'm unable to find it...
Simply put, my question is: how did people through history keep their swords rust-free? Nearly everything written on maintaining swords I could find relies heavily on modern products, like petroleum-based oils, vaseline, "Renaissance waxes", etc.

How were they maintained? Not just in medieval times (as far as I have read, majority of sources mention using unspecified "oil"), but even earlier. What would a Roman soldier or a wealthy Germanic tribesman use to maintain his sword?
My half-educated guess was animal fat, but since some animal fats have high salt content, I guess it would not have been so good for keeping rust off your blade.

Olive oil is the most common throughout, but it does depend on location and time period. There was a paper that looked at transport/trade in Roman olive oil by the army, and concluded that the volume was so ridiculously high that it could not have been just for consumption. The conclusion of the paper was rust prevention and weapons/armour maintenance. There are other written sources which further support this claim.

In other areas, i.e. Northern Europe, the general consensus is seal oil (rendered down from seal blubber, but in some areas i.e. Northern-Norway/Iceland whale blubber as well), linseed oil (from the Flax Plant), or oil rendered from fish bladders.

There was a very vast degree of trade, however, and it is silly to expect these geographic constraints to be fixed. Many places, i.e. Britain, Gaul (or later France, Germany, etc).. would have had a mixture of these various oils available, probably leaning to some in certain seasons/periods and then others later.

Keep in mind, further, that many sword/knife/blade scabbards were in period lined with fur which contains natural oils that help preserve and prevent rusting.

Best,
Hadrian

I suspect that most swordsmen had their own "secret recipe", or not-so-secret if they preached to all their friends how THAT particular oil or mixture was THE BEST. And the ingredients undoubtedly varied wildly.

It's been my own experience that it doesn't matter what you use, as long as you USE it. Clean your metal frequently, and it won't rust.

Olive oil was used for bathing and in lamps, so it's no surprise at all to see more than just cooking oil shipped all over the Empire!

I'm a 3-in-One guy. (Well, more of an "abuse and neglect" guy, but...)

Matthew

Lanolin the oil from sheep wool was likey one of the more common oils used.
A wool scabberd lineing also keep the sword softy in place and stop the blade fron kocking about in the scabbered.

Sheep wool and the lanolin thereof would definitely have been easily available throughout most of Europe, but I'm on board with the "seasonal" and "regular maintenance" ideas for the most part. People back then had less possessions in general, and took better care of what they did have, albeit they tended to use it a lot harder.