Table 1 A total of 70 emission and 70 excitation spectra on 37 lac dye paints were collected from 17 illuminated manuscripts produced in Portuguese monasteries (12th–13th c.). Based on their spectral features and intensity these spectra were assembled in 4 groups, Lac 1 to 4

Excitation maxima

473 nm

Band at 430 nm

535–555 nm

525 nm

sh 500 nm (resin chromophores)

sh 550–555 nm

554 nm

Intensity

 Max

4.2 × 10⁵

4.8 × 10⁵

6.5 × 10⁵

1.0 × 10⁶

 Min

1.3 × 10⁵

2.6 × 10⁵

2.2 × 10⁵

4.6 × 10⁵

Emission maxima

588–593 nm

sh 562 nm sh 615 nm

585–590 nm

sh 563 nm

sh 610–616 nm

585–590 nm

sh 610–616 nm

600–610 nm

592–594 nm sh 610 nm

Intensity

 Max

8.1 × 10⁴

9.2 × 10⁴

1.3 × 10⁵

9.3 × 10⁴

 Min

2.1 × 10⁴

3.4 × 10⁴

2.0 × 10⁴

3.6 × 10⁴