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1. Educational Linkage Approach In Cultural Heritage
E x e r c i s e 5.B
Advanced Course
Module 5 Monitoring & Maintenance
Topic 5.1 To Monitor or not to Monitor, that is the question!
Solution of Exercise 5.B
Hands on materials: how can we measure the colours?
Authors: Prof. Guido Biscontin, Dr. Francesca Caterina Izzo, Prof. Elisabetta Zendri, Ms. Laura Falchi- Ca’
Foscari University of Venice
Exercise 5.B part 1
Question: Consider the following colorimetric data measured on different samples (A, B and C). Sign the correct
position of the point in the CIE L*a*b* space.
Answer:
A= yellow
B= medium grey
A
A
B B C C= dark red
C
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2. Educational Linkage Approach In Cultural Heritage
E x e r c i s e 5.B
Exercise 5.B part 2
Calculate ∆E from the data reported in the following table.
samples ∆L ∆a* ∆b* ∆E
A 41 40 12 59
B 18 20 4 27
C -26 30 86 95
Exercise 5.B part 3
Consider the following colorimetric data measured after a conservation treatment expressed as difference
between the same sample before (not reported in the table) and after the treatment(samples A, B, C, D)
samples ∆E ∆L ∆a* ∆b*
A 2.7 -2.63 0.25 0.56
B 1.72 -1.68 0.16 0.33
C 1.77 -1.77 0.03 -0.11
D 14.02 3.50 -1.23 -0.51
Questions:
1) Is sample B more reddish than sample C?
2) Is sample A more yellowish than the others?
3) Is sample A more yellowish than D?
4) Do you think a protective treatment can change the colour of a surface, why?
5) Do you think the colorimetric data reported differ too much from the original sample (look at the ∆E
values)? Are these changes acceptable?
Answers:
1) Yes, it is.
2) Yes, it is, because it has the highest value of ∆a*.
3) Yes, it is.
4) Yes, because the application of the products can increase the brightness of the surface; sometimes the
products can become more yellow over the time and change the surface appearance.
5) The changes are all acceptable, with the exception of treatment D that has a ∆E value bigger than 5.
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