Tallow Soap Experiment

As anyone who has had a mild steel piece of armour knows, mild steel rusts.  Maille is no exception.  It has been said that perhaps the wrought iron of the Middle Ages was not so prone to rust as modern steels, due to the imbedded impurities (slag), which might serve to protect the iron from oxidation.  Yet even Chaucer describes his knight in The Canterbury Tales as having rust-checked clothing, having just returned from campaign.  Thus, it seems, even authentic armour was plagued with oxidation.

At Pennsic a year or so ago Jeffrey Hedgecock, of Historic Enterprises,  suggested an interesting solution.  According to Jeff, they use a bit of maille as a pot scrubber for cleaning dishes at living history events.  In addition, they use tallow soap.  Tallow soap, as you may know, is made from, among other things, rendered animal fat.  Jeff noticed that their maille pot scrubber seemed immune to rust, and thought it might be attributed to the tallow soap.  Perhaps washing maille in tallow soap might be a historical way to clean one's maille, and coat it to protect it against rust?

With this idea, I decided to conduct a crude experiment to see if perhaps tallow soap might provide some rust protection.  Mr. David Meyer generously mailed me a bar of his homemade tallow soap, which I used for the experiment.

The setup for the experiment included the following materials:


Two patches of mild steel riveted maille


"Orange Blast" degreaser


Water Hardener rock salt (99.5% sodium)


Tallow soap

The setup for the experiment.  Click to enlarge.

The first thing I did was to thoroughly clean both patches of maille with the degreaser, thus insuring that the maille was free of any contaminants or oils that might inhibit rust.

I then prepared a salt water solution by dissolving the salt shown above in a cup full of water. 

Next I washed one of the patches of maille with the tallow soap:

Washing a patch of maille with tallow soap.  Click to enlarge.

After washing the maille twice, with a good lather, I rinsed the maille.  I did not rinse it vigorously, but I did rinse it enough that the soap was noticeably gone.  I could tell right away that beads of water formed on the tallow-washed piece of maille, but not on the unwashed piece of maille.  This seemed promising, as it confirmed that the tallow soap had left a sort of waxy coating on the maille, causing the water to bead up.  I attempted to photograph this phenomenon but my camera could not focus clearly at a close enough range to capture it.

Finally, I dipped each piece of maille into the salt water, and left them each on their own paper plate to dry.  Periodically, over the next 48 hours, I would check on them, and if they were dry, I would dunk them both into the saltwater bath again.  I suppose I dunked them five or six times over the course of 48 hours.

It was obvious from the start that the tallow-washed piece of maille was not fairing much better than the unwashed piece.  At the end of the test, here is what the maille patches looked like:

After 48 hours.  Tallow-washed maille on left, unwashed on right.  Click to enlarge.

As you can see from the above pictures, there unfortunately seems to be little difference in rust between the two patches of maille.

I hope to conduct this experiment again in the near future, this time without rinsing the tallow soap from the maille, perhaps only toweling it off.

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