Saliva, the natural liquid formed inside an animal¡¦s mouth, has some surprising uses. For example, saliva contains special enzymes, amylase and lipase, which break down some of the starches and fats that can form solid, sticky materials. Thus, saliva helps __1__ food as soon as it enters the mouth. In addition, the slightly warm and acidic __2__ of this natural liquid have a particular benefit in one of the least likely environments.
That environment is the workshop of an art museum. Priceless antique paintings accumulate dust and dirt over time, causing darker and less colorful surfaces. The problem for conservators, trained specialists who clean and preserve artworks, is how to __3__ the built-up grime safely. They have many tools at their __4__. Surprisingly, human saliva is one of them.
Since human saliva is no-cost, sustainable, and non-toxic, it is ideally __5__ as
a cleaning agent. Working patiently and carefully, a conservator can slowly remove accumulation of grime from a surface. Thus, the artwork¡¦s __6__ paint colors can be seen just as they were when first painted. Traditionally, a layer of varnish was applied to paintings as a protective coating. The varnish not only protects the colors from __7__ but also acts as a surface for small particles to stick to. In most cases, a surface that has been varnished is easier for the conservator to clean than one that hasn¡¦t. Saliva, as it turns out, is one of the best __8__ for cleaning varnished artwork.
Art workshops are not the only surprising places where saliva shows its __9__. Soldiers in their barracks can tell you that the best shine one can make on a hard leather boot is by __10__ spit onto just-applied boot polish. If treated properly, the boot can be so shiny that you can even see your reflection in it!