Table 1 Ink contrast evaluation for the three performed 3-D X-ray CT scans.

From: Browsing through sealed historical manuscripts by using 3-D computed tomography with low-brilliance X-ray sources

Tube energy

Malachite

Iron Gall

Tyrian Purple

CRest

CRmsr

CRest

IG1: CRmsr

IG2: CRmsr

IG3: CRmsr

CRest

CRmsr

50 kV

1.74

0.90

1.49

0.32

1.24

4.23

1.03

0.07

40 kV

2.19

1.55

1.78

0.92

1.25

4.33

1.04

0.22

30 kV

2.98

1.76

2.32

1.12

1.55

4.68

1.06

0.45

  1. All writings, symbols and numbers were marked. From the mean value of the marked area and the page-only mean value, the contrast ratio (CRmsr) was determined for every scan and ink (higher values indicate improved visibility). The best contrast for all inks was measured with the 30 kV scan. The highest attenuation was measured for the iron gall ink with additional FeSO4 (IG3), followed by malachite ink, the original iron gall inks (IG1, IG2) and Tyrian purple. The estimated contrast ratio CRest and CRmsr are generally consistent.
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