Table 1 Overview of literature on colourimetric analysis of thermally altered skeletal remains, including used material, methodology, sample size and key findings on HI changes in colour.

Bonucci & Graziani (1975)

Archaeological human, archaeological non-human, and fresh non-human bone of 1 specie, modifications not provided.

Human cremated remains analysed from an archaeological context. Fresh non-human bone heated, unknown method, to 105 °C, 200 °C, 300 °C, 350 °C, 450 °C, 550 °C, 650 °C, 750 °C, 900 °C.

Not provided, at least N = 9/N = 1 for fresh non-human samples. (Subgroups based on temperature.)

Modifications not provided, subjective analysis; colour descriptions.

5 stages identified, provided colour descriptions. Associated temperatures based on the slopes of the thermogravimetric analysis.

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Shipman et al. (1984)

Fresh non-human bone, unmodified, of 2 species.

Muffle furnace, 11 pre-set temperatures (unheated, 185 °C, 285 °C, 360 °C, 440 °C, 525 °C, 645 °C, 675 °C, 745 °C, 800 °C, 870 °C, 940 °C), sample was in the oven during ramping, exposure duration 240 min. (excl. ramping), cooled in furnace for 240 min.

N = 60/N = 5 (Subgroups based on temperature.)

Unmodified bone, surface assessed. Subjective analysis; colour descriptions and Munsell colour chart comparison.

5 stages identified, provided colour descriptions and associated Munsell colour codes. Associated temperatures based on ranges of the oven.

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Nicholson (1993)

Archaeological bone and fresh non-human bone, unmodified, of different species (N = 6).

Muffle furnace, temperature range between 200 °C to 900 °C divided in steps of 100 °C with in addition an unheated group, exposure duration 150 min. No information provided on preheating or cooling down conditions.

N = 162/N = 3 (Subgroups based on temperature and species.)

Unmodified bone, surface assessed. Subjective analysis; Munsell soil colour chart.

Temperature associated dominant and minor colour codes provided. Differences found between species.

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Walker et al. (2005/2008)

Fresh human bone. Femoral diaphysis, small sections with an approximate weight of 1.5 g.

Muffle furnace, temperature range between 100 °C to 1200 °C divided in steps of 100 °C, exposure durations of 60, 120 and 180 min. Samples heated in air and 2 types of soil as media. No information provided on preheating or cooling down conditions.

Not provided, at least N = 108/N = 1. (Subgroups based on temperature, duration and surrounding medium.)

Unmodified sample, surface measured. Colourimetric data collected in RGB by means of a flatbed scanner.

Variables temperature, duration and surrounding media (thus oxygen availability) all contribute to the changes in colour.

^{16, 17}

Devlin et al. (2008)

Archaeological cremated human bone.

No samples experimentally exposed to heat, remains analysed from an archaeological context.

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Unmodified sample, surface measured. Colourimetric data collected in L*A*B* by means of a flatbed scanner.

Variation in discolouration mapped for the archaeological site. Subjective interpretation of temperature.

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Fredericks et al. (2015)

Fresh non-human bone, transverse sections, of 1 specie.

Muffle furnace, temperature range between 39 °C and 1000 °C divided in 23 subgroups, sample was in the oven during ramping, exposure duration 120 min. (excl. ramping), cooled at room temperature.

N = 69/N = 3 (Subgroups based on temperature.)

Bone milled to powder, powder measured. Colourimetric data collected in L*A*B* by means of a colourimeter.

The A* and B* coordinate changed in a similar fashion while the L* coordinate showed a different trend. Relative low standard deviations for the subgroups.

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Wärmlander et al. (2019)

Archaeological human bone that was experimentally cremated & fresh non-human bone, unmodified.

Muffle furnace, temperature range between 400 °C and 1000 °C, divided in steps of 200 °C, sample was in the oven during ramping, exposure duration 60 min. (excl. ramping), cooled in furnace for 240 to 480 min.

N = 13/N = 5 archaeological bone, N = 4 fleshed non-human and N = 5 defleshed non-human.

Unmodified bone, surface measured. Colourimetric data collected in L*A*B* by means of a spectrophotometer.

The data from the fleshed and defleshed samples led to identifiable clusters, archaeological bone showed a different discolouration after cremated when compared to fresh bone.

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