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Table 4 Overall colour variation (ΔE), changes in colour coordinates (Δa and Δb) and brightness (ΔL) for PUV1 (grain side) and PUV2 (corium side) parchment samples exposed to artificial ageing for a maximum of 748 h with respect to their unaged condition

From: Studies on the effects of mixed light-thermal ageing on parchment by vibrational spectroscopy and micro hot table method

SampleAgeing time (h)ΔLΔaΔbΔE
PUV1 (grain side)12− 0.280.482.482.54
830.080.230.930.97
2480.060.180.750.78
392− 0.920.301.331.64
748− 1.840.662.803.41
PUV2 (corium side)12− 2.07− 0.270.982.30
83− 1.47− 0.260.201.51
248− 1.58− 0.351.011.91
392− 1.88− 0.291.222.26
748− 0.35− 0.262.712.74