Four brightly colored calligraphic prints from the "Poem" series (1970/71) by Japanese artist Haku Maki (1924Maki ( -2000 were examined using multiple light-based analytical techniques in an effort to address conservation concerns regarding these artworks. A distracting white haze on the surface of some of the prints was determined by light microscopy and infrared microanalysis to be fungal mycelium from an inactive mold infestation that occurred prior to the artwork's acquisition by the museum. Pigment analysis by Raman, X-ray fluorescence, and infrared microspectroscopies identified the artist's palette as containing common printing ink colors such as aniline black (PBk1), carbon black (PBk7), phthalocyanine blue (PB15), Prussian blue (PB27), ultramarine blue (PB29), molybdate orange (PR104), chrome yellow (PY34), barium yellow (PY31), viridian (PG17), barium sulphate (PW21), and synthetic organic red pigments (PR3, PR22, PR48:3). Although aniline black and molybdate orange are common industrial pigments, reference vibrational spectra to assist in their identification have not appeared previously in the conservation literature. Moreover, this investigation includes to the authors' knowledge the first published identification of these pigments in a work of fine art. Haku Maki's unique 'cement-on-woodblock' printing technique in combination with his vibrant palette creates dynamic, embossed effects in these prints. However, lightfastness testing using a microfade tester identified the potential for light-based damage to the artwork, in some instances showing poorer lightfastness for colors reported to be stable pigments and greater stability than anticipated for others. These analyses are the first objective study of this innovative artist's material choices, and they enhance our understanding of his printing technique while helping to determine the proper stewardship protocols to protect his artistic legacy.

ATR–FTIR (attenuated total reflection–Fourier-transform infrared) microscopy with imaging is widely used in the heritage field to characterise complex compositions of paint cross-sections. However, some limitations include the need for ATR crystal contact with the sample and the inability to resolve particle size below the IR diffraction limit. Recently, a novel O-PTIR (optical-photothermal infrared) spectroscopy technique claimed to open a new avenue for non-invasive, efficient, and reliable analysis at sub-micron resolution. O-PTIR produces transmission-like FTIR spectra for interpretation, without the need to touch the sample, which are highly favourable attributes for analysing heritage samples. This paper reports the comparison of O-PTIR and ATR–FTIR techniques applied to a cross-section embedding a thin paint fragment that delaminated from a late 19th to early 20th-century oil portrait. The hazy paint fragment consisted of zinc soaps (both crystalline and amorphous), gordaite (NaZn4Cl(OH)6SO4·6H2O), and zinc lactate, that could not all be well-resolved with ATR–FTIR imaging. With O-PTIR analysis, the degradation compounds could be resolved at sub-micron resolution with an equivalent or better signal-to-noise ratio. This case study shows how the two techniques can be used to obtain comprehensive information at a broad level with ATR–FTIR and a detailed level with O-PTIR.

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Two Burmese oil paintings on zinc supports depicting portraits of royal families, dated to the early 20th century by Saya Aye and Saya Mya, showed interesting corrosion, efflorescence and soapy globules for analytical investigation prior to conservation for exhibition. The features and colours on the two paintings, one of which was in worse condition than the other, were obscured by a whitish haze. Paint rupture and losses due to corrosion of the zinc support were apparent. Using a combination of 3D digital microscopy, FTIR microscopy and SEM-EDS, the degradation, as well as the paint materials and artists' techniques were analysed and discussed. Zinc soaps, oxalates, silicates, hydroxychlorides, carbonates, wax and mould characterized the haze. Interestingly, brown outlines in Aye's painting appeared unusually dark. Upon analysis, this degradation phenomenon was attributed to micro-sized greenish soap globules that have developed around copper/zinc (brass) particles, causing the brown outlines to lose their intended luminosity. The other painting by Mya, in which the same brown outline was applied, did not show such formation of globules. Detection of oxalates in the corrosion of zinc support and brown outlines are discussed. This study shows the importance in understanding the artists' materials and techniques, which have consequential effects to the degradation observed.

Colour consistency is an important consideration when selecting pigments used on works of art. In this study, we analyse the colour difference between two sets of synthetic blue glass pigments acquired at least 8 years apart from the same manufacturer in Japan. The old pigment set (unused, dry powder with four different grain sizes) appears faded compared to the new set. These pigments are made available for artistic use, commonly in Nihonga or Japanese paintings. Raman spectroscopy and SEM-EDS results characterize these pigments as cobalt aluminate spinels dissolved in leaded glaze, a special class of complex coloured inorganic pigments that is not well-understood in the field of conservation. Colour difference between the old and new pigments with four different grain sizes were quantified by analysing photomicrographs with image analysis software. Blue pigments with coarse and extremely fine grains showed significant colour change compared to pigments with medium and fine grain sizes. The high occurrence of crystallites in the finer grains give a final colour that is bluer and lighter. Possible causes for the colour difference including manufacturing methods and storage environment are discussed.