Fading of a Single Colorant

Enter the parameters for the planned light exposure and then click the Compute Fading button.

(required when any of the above options are changed)

You searched for
  • RED Alizarin; paint in colorant
  • AND All the original colour in prior fade
  • AND 50 lux, the young see many objects well in intensity of light
  • AND 8 hours per day in exposure per day
  • AND Any flash exposures? in flash exposure
  • AND Zero flashes per day in flashes per day
  • AND Every day of the year in days per year
  • AND 100.0 in years

Calculated colour values

Original Current Future, with all UV removed Future, with UV (equiv. to daylight through glass)
RGB values
(251, 0, 72)
(251, 0, 72)
(255, 32, 76)
(255, 41, 78)
Dose Mlx∙h 0 0.0 14.6 14.6
ΔE (from original) 0 0.0 2.78 4.21
ΔE (from current) N/A 0 2.78 4.21
  • A value of ΔE=1.6 is approximately equal to a 'just noticeable fade'.
  • The dose of Mlx∙h in the current color is an estimated dose causing prior fade, assuming no UV. With UV, it would be estimated to be 0 Mlx∙h.

Colorant (RED Alizarin; paint) notes

Colorant comment:
Used in watercolours, oil paints, and acrylics. Invented in 1868, and replaced the natural pigment madder, which contains alizarin plus purpurin. Tends towards slight blue tone.

Colorant notes:
FADE: Colour Index gives alizarin lake, full tint, ISO 7; ½ tint, ISO 5. Feller et al (1984) report alizarin lake on paper as ISO 4-5. Calculator uses ISO 4.5. BENEFITS OF UV REMOVAL. Feller et al (1984) state the measured benefit for alizarin lake is "some." This suggests no more than x1.5. A cautious fit to McLaren’s (1956) data on the Blue Wools and 117 dyes suggests a typical benefit of UV removal of x3.2 for ISO 4.5 dyes. Calculator uses x1.5 for all alizarin and madder colorants.

Legal disclaimer
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