yellowing

1. 1
   noununcountable

   The process by which something changes to a yellow color.

   The yellowing of the manuscript pointed to centuries of exposure to air.

   Restorers worked carefully to reverse the yellowing in the painting's varnish.

   Similardiscoloration, fading

   Note

   Most of the time it names a gradual change as a whole, the way old paper or varnish darkens, but it can also be counted. Plant pathology uses the plural for individual patches of discoloration. Robert F. Nyvall's Field Crop Diseases Handbook (2013) describes "rusty spotting and yellowings" on the lower basal leaves. In that countable use, a yellowing is a symptom you can point to rather than a process.

2. 2
   verb

   Present participle of yellow.

   The varnish is yellowing with age, dulling the painting beneath it.

   Pages of the journal are yellowing where direct sunlight reaches them.

   Note

   The -ing form carries both halves of the verb. Usually it is intransitive, with something becoming yellow on its own (the varnish is yellowing). It can also take an object, as when smoke is yellowing a ceiling. A quick test: if something else is doing the coloring, the use is transitive. As a gerund it shades into the noun for the process, which, unlike the verb form, can be pluralized as yellowings.

   Years of cigarette smoke were yellowing the kitchen ceiling.

   Cheap acidic paper ends up yellowing every print stored against it.

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