Syllabus/achievement requirements

KONS3040 ¨C Advanced Painting Technology/Avansert kunstteknologi

Spring 2020

Course tutor: Associate Professor No?lle Streeton

 

NB

The pensum reading is not divided equally throughout the course. Students are encouraged to complete the reading in advance of lectures.

 

The Compendium (available from Akademika) should include all texts that are not available via a web-link.

 

 

Texts for purchase

Streeton, N.L.W. 2013. Perspectives on the Painting Technique of Jan van Eyck: Beyond the Ghent Altarpiece. London: Archetype Publications. ISBN 9781904982708 Nettpris: 753,-

 

 

 

Handy web-based resources

CAMEO: Conservation & Art Material Encyclopedia Online, materials database, see: http://cameo.mfa.org/

 

Anti-conservation organisation: ArtWatch: http://artwatchinternational.org/

 

Kress Reconstruction Project, University of Deleware (funded by the Kress Foundation):

http://www.artcons.udel.edu/about/kress

 

 

 

 

 

 

1. Changing pictures: external influences and internal mechanisms  

€ Ainsworth, M.W. ¡®From connoisseurship to technical art history: The evolution of the interdisciplinary study of art¡¯, Getty Conservation Institute Newsletter 20(1), 2005.http://www.getty.edu/conservation/publications_resources/newsletters/20_1/feature.html (accessed October 2017).

* Forni, U., ¡®The transfer of an oil painting from a panel to canvas (1866)¡¯, in Issues in the Conservation of Paintings, eds. D. Bomford and M. Leonard, Getty Conservation Institute, Los Angeles, 2004, 245¨C248.

* ?mile-M?le, G., ¡®The first transfer at the Louvre in 1750: Andrea del Sarto¡¯s La Charit¨¦ (1982)¡¯, in Issues in the Conservation of Paintings, eds. D. Bomford and M. Leonard, Getty Conservation Institute, Los Angeles, 2004, 275¨C289.

* Harding, E., and Oddy, A., ¡®Leonardo da Vinci¡¯s cartoon The Virgin and Child with St Anne and St John the Baptist¡¯, in The Art of the Conservator, ed. A. Oddy, British Museum Press, London, 1992, 28¨C41.

* van Eikema Hommes, M., ¡®Chapter 2. Painters¡¯ methods to prevent colour changes described in sixteenth to early eighteenth century sources on oil painting techniques¡¯, in Changing Pictures. Discolouration in 15th-17th-Century Oil Paintings, Archetype, London, 2004, 17?50.

*van Loon, A., ¡®Introduction¡¯, in Color Changes and Chemical Reactivity in Seventeenth-Century Oil Paintings, PhD Thesis, AMOLF (FOM Institute for Atomic and Molecular Physics) and the University of Amsterdam, 2008, 10?17.

* Keune, K., ¡®Introduction¡¯, in Binding Medium, Pigments and Metal Soaps Characterised and Localised in Paint Cross-Sections, PhD Thesis, AMOLF (FOM Institute for Atomic and Molecular Physics) and the University of Amsterdam, 2005, 2¨C12.

€ ¡®Why Some Paints are Transparent and Others Opaque?¡¯ http://www.naturalpigments.com/art-supply-education/transparent-opaque-paints/ [2 pages]

 

 

 

 

2. Conservation and change / Change and conservation

Durable materials

* Merrifield, M.P., ¡®Bolognese Manuscript¡¯, in Medieval and Renaissance Treatises on the Arts of Painting, 2 vols., Dover Publications, Mineola (NY), 1999. (Original: Original Treatises dating from the XIIth to XVIIth centuries on the arts of painting, in oil, miniature, mosaic, and on glass, John Murray, London, 1849). Read: ¡®Preliminary observations¡¯, pp. 325¨C339; pp. 340¨C404, making a good blue; pp. 418¨C430, making copper greens; p. 428, making ¡®lead-tin¡¯ yellow; pp. 432¨C456, making lakes; pp. 478¨C480, making vermilion; p. 484, making lead white.

€ Coccato, A., Moens, L. and Vandenabeele, P., On the stability of mediaeval inorganic pigments: a literature review of the effect of climate, material selection, biological activity, analysis and conservation treatments, Heritage Science 5, 2017. https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-017-0125-6

* Carlyle, L., The Artist¡¯s Assistant: Oil Painting Instruction Manuals and Handbooks in Britain 1800¨C1900 with Reference to Selected Eighteenth-Century Sources, Archetype, London, 2001, 1?54.

 

Degradation

€ Monico, L., van der Snickt, G., Janssens, K., De Nolf, W., Miliani, C., Verbeeck, J., Tian, H., Tan, H., Dik, J., Radepont, M., and Cotte, M., ¡®Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of Synchrotron X-ray Spectromicroscopy and related methods. 1. Artificially aged model samples, Analytical Chemistry 83, 2011, 7 pages. https://pubs.acs.org/doi/10.1021/ac102424h

€ Keune, K., Boon, J., Boitelle, R., and Shimadzu, Y., ¡®Degradation of Emerald green in oil paint and its contribution to the rapid change in colour of the Descente des vaches (1834¨C1835) painted by Th¨¦odore Rousseau, Studies in Conservation 58(3) 2013, 199?210. https://www.tandfonline.com/doi/full/10.1179/2047058412Y.0000000063

 

Cleaning and restoration

* Stols-Witlox, M., ¡®Historical restoration recipes: the cleaning of oil paintings 1600?1900¡¯, in ICOM-CC 16th Triennial Conference, Lisbon, 19?23 September 2011, ed. J. Bridgeland, Crit¨¦rio, Almada, 2011, 7 pages.

* Walden, S., The Ravished Image: Or, How to Ruin Masterpieces by Restoration, Weidenfeld, London, 1985, 1?23.

* Hedley, G., ¡®Cleaning and meaning: The Ravished Image reviewed¡¯,The Conservator 10, 1986, 2?6. (Reprinted in Measured Opinions: Collected Papers on the Conservation of Paintings, ed. C. Villers, UKIC, London, 1993, 167?171).

€ Sciolino, E., ¡®Leonardo painting¡¯s restoration bitterly divides art experts¡¯, New York Times, 3 January 2012, http://www.nytimes.com/2012/01/04/arts/design/clash-over-restoration-of-leonardos-virgin-and-child.html?_r=2&ref=global-home

 

 

 

Lecture 2, cont. Further reading (external to pensum):

Carlyle, L., and Witlox, M., ¡®Historically accurate reconstructions of artists¡¯ oil painting materials¡¯,  Tate Papers, Spring 2007, 5 pages. http://www.tate.org.uk/research/tateresearch/tatepapers/07spring/carlyle.htm

Cennino d¡¯Andrea Cennini, The Craftsman¡¯s Handbook ¡°Il Libro dell¡¯ Arte¡±, trans. and ed. D.V. Thompson, Jr, Dover Publications, New York, 1960 (Original: Yale University Press, New Haven, 1932), 20?39.

Clarke, M., 2001, The Art of All Colours. Medieval Recipe Books for Painters and Illuminators, Archetype Publications, London, 3.

Doerner, M., 1969, The Materials of the Artist and Their Use in Painting with Notes on the Techniques of the Old Masters, trans. E. Neuhaus, revised edn, Rupert Hart-Davis Ltd., London. [original: 1933, Malmaterial und seine Verwendung im Bilde, Stuttgart].

Eastlake, C.L., 1960, Methods and Materials of the Great Schools and Masters, Vol. 1, Dover Publications, New York.

Karg¨¨re, L. & Marincola, M. 2014. Conservation in context: The examination and treatment of polychrome wood sculpture in the United States. Metropolitan Museum Studies in Art, Science, and Technology 2, 11?50.https://www.nyu.edu/gsas/dept/fineart/people/faculty/marincola_PDFs/MMSAST2_Kargere_Marincola.pdf

Massing, A., 1990, ¡®Painting materials and techniques: towards a bibliography of the French literature before 1800¡¯, Die Kunst und ihre Erhaltung: Rolf E. Straub zum 70. Geburtstag gewidmet, Wernersche Verlagsgesellschaft, Worms, 57-96.

Packard, E. C. G. 1967. The preservation of polychromed wood sculpture by wax immersion and other methods. Museum News Technical Supplemet, American Association of Museums 46, 47-52.

Plahter, U., ¡®Colouring materials and binding media¡¯, in U. Plahter, Painted Altar Frontals of Norway, 1250¨C1350. Volume 2: Materials and Technique, Archetype, London, 2004, 138¨C182.

Roosen-Runge, H., 1973, Farbgebung und technik Fr¨¹hmittelalterlicher Buchmalerei : Studien zu den Traktaten ¡®Mappae Clavicula¡¯ und ¡®Heraclius¡¯, 2 vols., Deutscher Kunstverlag, Munich. (An attempt to find relationships between sources and technical analyses of book paintings.)

Theophilus Presbyter, On Divers Arts. The Foremost Medieval Treatise on Painting, Glassmaking and Metalwork, trans. J.G. Hawthorne and C.S. Smith, revised, Dover Publications, Mineola (NY), 1979.

Thompson, D.V., 1956, The Materials and Techniques of Medieval Painting, Dover Publications, New York. [original: 1936, G. Allen and Unwin, London]

Woudhuysen-Keller, R., and Woudhuysen, P., ¡®Thoughts on the use of the green glaze called ¡°copper resinate¡± and its colour-changes¡¯, in Looking Through Paintings. The Study of Painting Techniques and Materials in Support of Art Historical Research, ed. E. Hermens, de Prom, Baarn, 1998, 133¨C146.

 

 

 

 

3. The changing appearance of the Ghent Altarpiece: a case study

* Coremans, P., ¡®The technique of the ¡°Flemish Primitives¡¯¡±, in Issues in the Conservation of Paintings, eds. D. Bomford and M. Leonard, Getty Conservation Institute, Los Angeles, 2004, 194¨C206.

* Dubois, H., and van Grevenstein-Kruse, A., ¡®Bridging controversy: the contribution of an international commission of experts to the 1950?51 study and treatment of van Eyck¡¯s Ghent Altarpiece¡¯, in ICOM-CC 16th Triennial Conference, Lisbon, 19?23 September 2011, ed. J. Bridgeland, Crit¨¦rio, Almada, 2011, 5 pages.

* Streeton, N.L.W., ¡®The Ghent Altarpiece: rethinking the paradigm¡¯ (Chapter 3) in Perspectives on the Painting Technique of Jan van Eyck: Beyond the Ghent Altarpiece, Archetype Publications, London, 2013, 45?56.

* Streeton, N.L.W., ¡®Problems and strategies for a technical history for the paintings of van Eyck¡¯ (Chapter 7) in Perspectives on the Painting Technique of Jan van Eyck: Beyond the Ghent Altarpiece, Archetype Publications, London, 2013, 135?141.

€ van der Snickt, G., Miliani, C., Janssens, K., Brunetti, B.G., Romani, A., Rosi, F., Walter, P., Castaing, J., De Nolf, W., Klaassen, L., Labarque, I., and Wittermann, R., ¡®Material analyses of ¡®Christ with singing and music-making Angels¡¯, a late 15th-C panel painting attributed to Hans Memling and assistants: Part I. non-invasive in situ investigations¡¯, Journal of Analytical Atomic Spectrometry 11, 2011, 2216?2229,
http://pubs.rsc.org/en/content/articlelanding/2011/ja/c1ja10073d.

 

 

4. The artist¡¯s intentions: problems for conservation

* Dykstra, S.W., ¡®The artist¡¯s intentions and the intentional fallacy in fine arts conservation¡¯, Journal of the American Institute for Conservation 35(3), 1996, 197?218.

* Skaug, E.S., ¡®Cleaning controversies and ¡°the two cultures¡±: steps towards professional autonomy¡¯, in ICOM Committee for Conservation, 11th Triennial Meeting Edinburgh, 1?6 September 1996 1996, Preprints Volume I, ed. J. Bridgland, James and James, London, 1996, 177?181.

* Hedley, G., ¡®Long lost relations and new found relativities: issues in the cleaning of paintings¡¯, in Appearance, Opinion and Change: Evaluating the Look of Paintings. Preprints of the UKIC/AAH Conference, June 1990,eds. P. Booth and V. Todd, UKIC, London, 1990. (Reprinted in Measured Opinions: Collected Papers on the Conservation of Paintings, ed. C. Villers, UKIC, London, 1993, 172?178.)

* Mancusi-Ungaro, C., ¡®Original intent: the artist`s voice.¡¯ in Modern Art: Who cares?. eds. I. Hummelen and D. Sill¨¦, Foundation for the Conservation of Modern Art and the Netherlands Insitute for Cultural Heritage, Amsterdam, 1999, 392?393. [1.5 pages]

* Hermens, E., ¡®The artist¡¯s position in conservation¡¯, in Modern Art: Who cares?. eds. I. Hummelen and D. Sill¨¦, Foundation for the Conservation of Modern Art and the Netherlands Insitute for Cultural Heritage, Amsterdam, 1999, 397?399. [1.5 pages] 

Re-read: ECCO Professional Guidelines I/II/III, ECCO, Brussels (2002). See http://www.ecco-eu.org/about-e.c.c.o./professional-guidelines.html or Google ECCO Professional Guidelines for the link to the pdf.

 

5. Norsk kirkekunst: Forandring av original sammenheng og overmaling siden 1200-tallet (Professor Tine Fr?ysaker)

€ Fr?ysaker, T., ¡®Otter?ykrusifikset ¨C kilde til middelalderhistorie¡¯, in NIKU 1994?1999, Kulturminneforskningens mangfold, eds. G. Gundhus, E. Seip og E. Ulriksen, NIKU Temahefte 31, 1999, 79?89. http://www.niku.no/filestore/Publikasjoner/NIKUTemahefte31.pdf

€ Gjertsen, R., Den korsfestede Kristus fra Skafs?s kirke. Tokke kommune i Telemark. Unders?kelser og konservering, NIKU Publikasjoner 123, 2002, 1?34 (Les 3?5, 7, 10?17). http://www.niku.no/filestore/Publikasjoner/NIKUPublikasjoner123.pdf

€ Fr?ysaker, F., ¡®Hvordan middelalderens krusifikser ble laget¡¯, in Kors og krusifiks. Tre utsnitt av deres historie, eds. A.J. Brendalsmo, T. Fr?ysaker and J.H. Jensenius, NIKU Publikasjoner 105, 2001, 1?46 (Les s. 13-22. I alt 5,5 sider). http://www.niku.no/filestore/Publikasjoner/NIKUPublikasjoner105.pdf

€ Fr?ysaker, F., Den bemalte og forgylte kalvariegruppen fra 1100-tallet i Urnes stavkirke. Konservering 2001?2003, NIKU Rapport 3, 2003, 1?89. (Les s. 3, 8-10, 15-19, 30-34, 38-39. I alt 13,5 sider). http://www.niku.no/filestore/Publikasjoner/NIKURapport3.pdf

€ Olstad, T.M., Alterskapet i Grip stavkirke. Et 1700-talls alterskap fra middelalderen. Konservering 2001?2003, NIKU Rapport 5, 2003, 1?59. (Les s. 3, 5, 7-33. I alt 20 sider). http://www.niku.no/filestore/Publikasjoner/NIKURapport5.pdf

* Fr?ysaker, F., ¡®Maleriene i Vats kirke¡¯, in Vats kyrkje 150 ?r, 2005, 25?32. (Les s. 25-29. I alt 3,5 sider)

€ Olstad, T.M., Alterskapet fra senmiddelalderen i Hadsel kirke ¨C et alterskap attribuert til Lekagruppen. Unders?kelse og behandling av alterskapet. Oppm?ling av fire alterskap i Lekagruppen, NIKU Rapport 21, 2008, 1?83. (Les s. 3, 27-33. I alt 8 sider) http://www.niku.no/filestore/Publikasjoner/NIKURapport21.pdf

€ Kollandsrud, K., Krusifiks fra Haug kirke. Varia 27. Oslo: Universitetets Oldsaksamling, 1994, 16-19, 93-111. https://www.duo.uio.no/handle/10852/66791

 

 

 

NEW

6. ¡®Transformation¡¯: Late-medieval church art and its afterlife in Norway

* Streeton, N.L.W., Platania, E., Daly, A., Vila, A. & Buti, D. 2018, Tapte relasjoner? / Long-Lost Relations? In Bjerregaard, P. ed. Forvandling: Tro og hellige gjenstander i middelalderen / Transformation: Faith and Sacred Objects in the Middle Ages, pp. 30¨C43. Trondheim: Museumsforlaget. 

€ Daly, A. & Streeton, N.L.W., Non-invasive dendrochronology of late-medieval objects in Oslo: refinement of a technique and discoveries. Applied Physics A 123:431, 2017, 12 pp. Open Access: https://link.springer.com/article/10.1007/s00339-017-1019-x

€ Streeton, N.L.W., Decoding damages to late-medieval cult sculpture from Norwegian churches. In Janet Bridgland (ed.), ICOM-CC 18th Triennial Conference Preprints, Copenhagen 4-8 September 2017, Linking Past and Future. International Council of Museums, ICOM, Paris, 2017. http://icom-cc-publications-online.org/PublicationDetail.aspx?cid=662bcd86-bb75-41fc-9f08-875f3b9d7837  

€ Streeton, N.L.W. 2019. Final report. After the Black Death: Painting and Polychrome Sculpture in Norway https://www.hf.uio.no/iakh/english/research/projects/medieval-painting/index.html.

€ Streeton, N.L.W. 2018. Perspectives (old and new) on late-medieval church art in Norway: questioning the hegemony of L¨¹beck workshops. Scandinavian Studies 90:1: 50?77. https://muse.jhu.edu/article/701920

 

 

 

7. Changing objects and material culture: theoretical perspectives for conservation

€ Streeton, N.L.W. Writing histories for late-medieval objects: the engagement of conservation with theoretical perspectives on material culture, Studies in Conservation 62:7 (2017) 419-31: http://dx.doi.org/10.1080/00393630.2016.1210752

€ Ford, T., Brief Report: ?douard Manet¡¯s ¡®A View of the 1867 Exposition Universelle¡¯, Nasjonalmuseet (Oslo) (2011) 6 pp. http://harriet.nasjonalmuseet.no/manet/media/download/conservationreport.pdf

 

 

 

 

 

 

8. Lucas Cranach: results and perspectives of technical research (Professor Gunnar Heydenreich)

* Heydenreich, G., ¡®¡­that you paint with wonderful speed¡¯ Virtuosity and efficiency in the artistic practice of Lucas Cranach the Elder¡¯/¡®¡­dass Du mit wunderbarer Schnelligkeit malest¡¯ Virtuosit?t und Effizienz in der k¨¹nstlerischen Praxis Lucas Cranachs d.?.¡¯, in Cranach der ?lter, ed. B. Brinkman, (St?del Museum, Frankfurt am Main, 23 November 2007¨C17 February 2008), St?del, Frankfurt, 2007; Royal Academy of Arts, London, 2008, 29¨C47.

* Heydenreich, G., Carson, D., Grzywacz, C., Khanjian, H., Mazurek, J., Schilling, M., ¡®Painting on white canvas: Sixteenth century bleaching practices and the analysis of morphological and chemical changes in flax fibres¡¯, in ICOM-Committee for Conservation, 15th Triennial Meeting, New Delhi, 22?26 September 2008, ed. J. Bridgland, Allied Publishers Ltd., New Delhi, Vol II., 2008, 609?618.

€ Task: navigate the Cranach Digital Archive at http://www.lucascranach.org/relatedprojects_en.html

 

 

9. Munch¡¯s Aula Paintings: Are they preserved? (Professor Tine Fr?ysaker)

€  Fr?ysaker, T., Liu, M., ¡®Four (of eleven) unvarnished oil paintings on canvas by Edvard Munch in the Aula of Oslo University: Preliminary notes on their materials, techniques and original appearances¡¯Restauro 1, 2009, 44?62.¡¯

 

 €  Fr?ysaker, T., ¡¯Bevaring av Edvard Munchs Aulamalerier f?r og n?¡¯Kunst og Kultur 1, 2008, 2?17.

.

* Shimadzu, Y., Keune, K., van den Berg, K.J., Boon, J.J., and Townsend, J.H., ¡®The effects of lead and zinc white saponification on surface appearance of paint¡¯, in ICOM-Committee for Conservation, 15th Triennial Meeting, New Delhi, 22?26 September 2008, ed. J. Bridgland, Allied Publishers Ltd., New Delhi, Vol II., 2008, 626?632.

* Koller, J., and Burmester, A., ?Blanching of unvarnished moderen paintings: a case study on a painting by Serge Poliakoff¡¯, in Cleaning, Retouching and Coating. Contributions to the IIC Brussels Congress, 3?7 September 1990, eds. J. Mills and P. Smith, IIC, London, 1990, 138?143.

 

Further reading (external to pensum):

Fr?ysaker, T., with Streeton, N., Kutzke, H., Hanssen-Bauer, F. & Topalova-Casadiego, B. 2015. Public Paintings by Edvard Munch and His Contemporaries: Change and Conservation Challenges. London: Archetype Publications, London. ISBN 9781909492387

Fr?ysaker, T., Miliani, C., and Liu, M., ¡®Non-Invasive Evaluation of Cleaning Tests Performed on ¡°Chemistry¡± (1909?1916), a Large Unvarnished Oil Painting on Canvas by Edvard Munch, Restauro (4) 2011, 53?63.

Noble, P. and Boon, J.B., ¡®Metal soap degradation of oil paintings: aggregates, increased transparency and efflorescence¡¯ in AIC Paintings Speciality Group Postprints, Vol. 19, AIC, Washington, D.C., 2007, 1¨C15.

van der Weerd, J., et al. ?Zinc soap aggregate formation in ¡¯Falling Leaves¡¯ (Les Alyscamps) by Vincent van Gogh¡¯, Zeitschrift f¨¹r Kunsttechnologie und Konservierung 17(3), 2003, 407?416.

 

10. The deterioration of modern materials (Laura Homer, Painting Conservator, Nasjonalmuseum)

* Learner, T., ¡®Modern paints: uncovering the choices¡¯, in Modern Paints Uncovered, Proceedings from the Modern Paints Uncovered Symposium, Tate Modern, London May 16-19, 2006. eds. T. Learner, P. Smithen, J.W. Krueger og M.R. Schilling, Getty Publications, Los Angeles, 2007, 3?16.

€ Jablonski, E., Learner, T., Hayes, J., and Golden, M., ¡®Conservation concerns for acrylic emulsion paints: a literature review¡±, Tate Papers, Autumn 2004, http://www.tate.org.uk/research/publications/tate-papers/02/conservation-concerns-for-acrylic-emulsion-paints-literature-review

€ Ormsby, B., and Learner, T. ¡®The effects of wet surface cleaning treatments on acrylic emulsion artists' paints ¨C a review of recent scientific research¡¯, Studies in Conservation, 2009, 29?41 http://www.tandfonline.com/doi/abs/10.1179/sic.2009.54.Supplement-1.29

* Pullen, D., ¡®Managing change ¨C the conservation of plastic sculptures¡¯, in Material Matters, The Conservation of Modern Sculpture, ed. Jackie Heuman, Tate Gallery Publishing, London, 1999, 101?107.

* Stringari, C., ¡®Installations and problems of preservation¡¯, in Modern Art: Who cares?. eds. I. Hummelen and D.  Sill¨¦, The Foundation for the Conservation of Modern Art and Netherlands Insitute for Cultural Heritage, Amsterdam, 1999, 272?281.

* Hummelen, Y., and Scholte, T., ¡®Collecting and archiving information from living artists for the conservation of contemporary art¡¯, in Conservation of Easel Paintings, eds. J. Stoner and R. Rushfield, Routledge, London, 2012, 39?47.

* Smithen, P., ¡®A history of the treatment of acrylic painting¡¯, in Modern Paints Uncovered, Proceedings from the Modern Paints Uncovered Symposium, Tate Modern, London May 16-19, 2006. eds. T. Learner, P. Smithen, J.W. Krueger and M.R. Schilling, Getty Publications, Los Angeles, 2007, 165?174.

 

 

Further reading (external to pensum):

Barker, R., and Bracker, A., ¡®Beuys is dead: long live Beuys! Characterising volition, longevity, and decision-Making in the work of Joseph Beuys¡±, Tate Papers, Autumn 2005. Tilgjengelig p?: http://www.tate.org.uk/research/tateresearch/tatepapers/05autumn/barker.htm

Wharton, G., ¡®INCCA: A Model for Conserving Contemporary Art¡¯, in Conservation Perspectives, The GCI Newsletter 24.2, 2009. Tilgjengelig p?: http://www.getty.edu/conservation/publications_resources/newsletters/24_2/incca.html

 

 

 

Published Nov. 22, 2019 5:42 PM - Last modified Nov. 22, 2019 5:42 PM