Definition of lightfastness in US English:

lightfastness

noun

  • See lightfast

    • ‘Label the swatches carefully, and expose to direct sunlight or a commercial lamp of the type used for testing lightfastness.’
    • ‘When you've painted all the colors you want to test for lightfastness, cut the sheet in half.’
    • ‘If a pigment has good lightfastness, it does not always mean that it has good weatherfastness’
    • ‘This pigment identification project and a lightfastness standard can only lead to the increased recognition of this fine art medium.’
    • ‘Earth colors are rated ASTM Lightfastness I - the highest lightfastness rating.’