当艺术品保管员 彼得里亚•诺贝尔 正打算清洁一幅有将近400年历史的伦勃朗的画时
When art conservator Petria Noble was preparing to clean a nearly 400-year-old Rembrandt,
she noticed its surface was riddled with microscopic pockmarks.
And Petria is not alone.
Other conservators have reported the strange phenomenon on thousands of other oil paintings.
In addition to threatening the splendor of these priceless pieces of art,
the blemishes are driving some in the art world crazy.
But researchers finally know what’s creating the strange craters.
Petria first noticed the pockmarks under the microscope in 1996.
As it turns out, decades before she came on the scene,
other museum researchers had also seen the craters.
Her predecessors speculated that tiny gas bubbles had percolated out of the painting,
leaving the pockmarks behind.
Petria wanted to understand the anatomy of the pockmarks,
which by the way is awesome, because it’s metal,
the painting is called “Anatomy Lesson of Dr. Nicolaes Tulp.”
So anyway, she carefully removed tiny cross-sections from several craters.
It turns out that many of the craters contained a white muck,
that kinda looks like insect eggs.
But these white lumps are neither insect eggs nor gas bubbles.
Petria and her collaborators figured out that the strange white muck is actually lead soap.
Like the soap Rembrandt might have used to wash his hands after a long day of painting.
Only, instead of being produced by 16th century cosmetic makers,
this lead soap is a product of the painting itself.
And don’t worry.
Your bar of soap doesn’t have lead in it–it contains sodium or potassium instead.
The lead soap formed over many years within the artwork when lone fatty acids from the
oil paint encountered meandering lead ions from pigments.
Metal soaps are often bad news.
When they form at or near a painting’s surface, they can burst through leaving pockmarks that
留下使画作看起来模糊 有沙砾感 且阴暗的凹坑
make art look hazy, gritty, and dull.
The soaps can also leave disfiguring crusts and reflective films on the painting.
But the problems get worse if enough metal soap forms deep within a painting.
The slippery soap can cause something called delamination.
That’s when layers of paint deform, lift up, and flake off–not really something you
want in a piece of artwork whose value is measured in millions of dollars per square meter
Understanding what’s going on in these masterpieces,
has required that scientists literally watch paint dry.
Here’s what they’ve found.
The oil in oil paint usually comes from linseed plants–also known as flax seed.
Linseed oil features a glycerol backbone which can support a variety of fatty acids, such
as linolenic acid.
When exposed to air the fatty acids polymerize into a complicated mesh that becomes the tough
material which you may know as “dry paint.”
Besides oil, every paint also contains its own peculiar mixture of colorful pigments
and additives that, for example, help maintain the paint’s texture and stability.
But it turns out that the incredibly complicated chemical system we call dry paint is not always stable.
Over time, heat and humidity sever the fatty acids from the paint’s glycerol backbone.
These negatively charged fatty acids wander through paint’s polymer matrix until they’re
drawn to positively charged metal ions like lead and zinc, which are used in pigments.
The fatty acids and metal marry to form soap, which accumulate into white lumps.
世界各地的艺术品保管员已经在弗朗西斯科•徳 戈雅 文森特•梵高
Conservators around the world have discovered soaps in artwork by Francisco de Goya, Vincent
Van Gogh, Piet Mondrian, Georgia O’Keefe and many others.
Artwork from the 13th century to modern day.
Although we understand the basic chemistry behind the metal soaps, conservators are still
trying to figure out the best ways to clean these soap-laden paintings–and whether cleaning
is even a good idea.
这是因为 对保管员来说 可行的最安全的清理策略之一
That’s because one of the safest cleaning strategies available to conservators–namely
using good old water–may actually accelerate metal soap formation.
So what do you think?
Is it worth the risk to try to clean these works of art?
Or should we just learn to appreciate the haze from metal soaps,
like we do with the green patina of oxidized copper?
Tell us what you think in the comments.
当艺术品保管员 彼得里亚•诺贝尔 正打算清洁一幅有将近400年历史的伦勃朗的画时