How do you clean a nearly 140-year-old oil painting? Well, if you're Manitoba Museum conservator Carolyn Sirett, you roll up your sleeves, roll a cotton swab and put your muddy where your mouth is.

Dirt doesn't stand much of a chance against the power of human saliva, apparently.

There are solid scientific reasons for giving something the old spit shine, or for licking your wounds. Saliva contains enzymes that break down food particles as well as infection-battling white blood cells that are effective at killing bacteria.

For museum conservators, that means a natural and chemical-free way to lick built-up grime and mould found on artifacts. Well, not literally.

"I'm not actually spitting on or licking mould off the paintings," said conservator Carolyn Sirett, who is responsible for the long-term preservation of 2.9 million specimens in the museum's collection

A cotton swab is hand-rolled then lightly dampened in the mouth, preferably prior to lunch, she explained.

The swab is then rolled on the surface being cleaned. Once dirty, it is tossed and the process repeated. Over and over until the artifact is clean.

Fort Garry, 1869 Lionel Stephenson

The condition of an oil painting by Lionel Stephenson, titled Fort Garry, 1869, before a saliva treatment. (Manitoba Museum)

Fort Garry, 1869 Lionel Stephenson

The condition of Lionel Stephenson's painting after a saliva treatment. (Manitoba Museum)

"Tests are always done prior to a full cleaning to make sure materials that we want to stay on the artifact, stay there," Sirett said.

Another nice thing about spit is that it is readily available and free. It also eliminates the need for chemical cleaning agents, some of which are carcinogenic.

"If you can avoid that, you definitely want to. A lot of conservators now are using much more environmentally-conscious materials but at the same time, you might have to use those [others] sometimes," Sirett said.

"We always start from the least invasive way as possible if we can."

A range of artifacts can be cleaned with the saliva technique, including leather, beading, wooden surfaces, ceramics, glass, and of course, oil paintings. 

Because of the variety of materials they work with, conservators need to have a wide understanding of manufacturing processes, taxidermy, and the history of technology.

Manitoba Museum uses spit to restore art0:29

Sirett deals with thousands of types of adhesives, and depending on the materials that make up the artifact — ink, paper, feathers, leather, paint — they can all have distinct effects.

If something is metal, for instance, she needs to know if it is steel or iron and how was it forged. All of that will impact how something ages or corrodes.

Sirett also needs to know a little about pest control and to take into account evils like humidity, light, and temperature, which can damage objects in the museum.

That's why it's dim and often cool in the galleries, which Sirett walks through every morning.

There's a lot to consider in order to ensure artifacts are there for subsequent generations to enjoy. But Sirett says she worries about the challenges conservators who come after her will face as a result of the modern infatuation with plastic.

Cellphones, cameras, toys, computers, and even cars are made from plastic. Very little is known about how long it will last and what can be done to protect it from the ravages of time. Plasticizer — a substance added to a synthetic resin to aid in flexibility — eventually wears down and turns the material chalky and brittle.

"I feel sorry for future conservators," Sirett said.

Carolyn Sirett

Carolyn Sirett looks over the back of an 1800s charter from the Independent Order of Foresters, a fraternal organization like the masons or elks. The paper has yellowed due to an acidic wooden backing on the frame it was in for many years. ​ (Darren Bernhardt/CBC)