We all sweat.
Some of us do it rather profusely, particularly when life suddenly gets a tad more exciting or stressful than usual. Such as on your wedding day. Or during military combat. Or on your coronation day—if you happen to be royalty.
Clothing worn during historically important events often finds its way to museums, and that’s when a textile conservator will take a good look—and possibly a deep sniff—in an outfit’s armpit region.
According to four textile conservators who humored my—as it turns out—not so absurd sweat stain inquiry, armpit areas can be colored yellow (no surprise there), but also green, orange, brown and red. The quirkiest sweat stain reported was “a grey-green tide-line stain… with a pinkish interior.”
Staining can depend on a myriad of factors, such as the individual wearer’s sweat chemistry, the fabric, the dye, and whether the person was wearing deodorant or antiperspirant.
Consider the case of a World War II wedding dress that crossed Jessie Firth’s conservation table at the Australian War Memorial. Worn by five different women in the 1940s, the pretty beige dress had green armpits.
Firth figured out that the culprit was a decorative copper thread in the dress that was corroded by the armpit sweat, producing the green patina you normally see on copper-plated architecture. Sweat is a rather complicated mixture of proteins, fatty acids and other molecules, but the lactic acid, salt and ammonia constituents may have all helped corrode the copper wire so that the dress stained green.
Proteins in sweat are probably to blame for the most common yellow stain. These proteins may become tightly fixed to the fabric by the aluminum salts in deodorants and antiperspirants--but this is still debated.
Some red stains may come from an early formulation of a popular antiperspirant called Odorono (Odor-Oh-No!), which was launched in the 1910s and was initially red in color. (Random aside: The Who once wrote a satirical song about Odorono. But I digress.)
The question is what to do about the sweat stains? There’s the increasingly popular "hands-off" philosophy in art conservation circles which argues that even the most benign-seeming treatment may cause some long-term harm, so it's best to avoid any superfluous interventions on artifacts.
In addition, the sweat itself may have some important historical value.
For example, if Queen Elizabeth II’s coronation dress had sweat stains, no conservator in their right mind would remove that important historical information about her emotional state at the time—although it could just be information about the June day’s ambient weather. (But is it ever really that hot in England?)
On the other hand, decade- or century-old perspiration can weaken a garment’s underarm area causing irreparable damage; it can mess with dye chemistry; and in the case of some NASA moon-mission space suits, leftover astronaut sweat even corroded the outfits’ aluminium zippers, making them impossible to safely open or close.
If the clothing’s owner wore deodorants and antiperspirants (which became popular in the 20th century), the salts used in their formulation could also make the fabric more brittle and prone to breaking.
Furthermore, sweat can also tempt tiny fabric-munching pests to feast on an important outfit. “There are also many examples where insects have preferentially eaten underarm and crotch areas,” Firth explained. “Our suspicion is that these areas are tastier to the insects due to the presence of sweat and body oils.”
Another problem if the wearer used a dress shield (now known as a sweat pad) to absorb perspiration, the dress shield’s rubber components will degrade, causing browny orange stains, said June Bové, a longtime textile conservator who teaches at the Fashion Institute of Technology.
Bové advocates removing dress shields because the rubber degradation always does irrevocable harm. But the decision about whether and how to clean an important outfit’s armpits often requires serious discussion between curators, conservators and other museum staff, she adds.
I bet that the people who wore these historial garments never dreamed that the output of their armpits would produce such deliberation and debate.
These green sweat stains on a WW2 wedding dress appeared after sweat corroded the copper threads in the fabric. Credit: Australian War Museum