6. Exploiting Weave Maps
C. Richard Johnson, Jr.
When looking directly at an X-radiograph of a canvas, it is difficult to see patterns in the variations of the threads. The thread density maps and angle maps (collectively called weave maps), described in the previous chapters, help display the underlying patterns more clearly. Weave maps can be used in several ways to gain insight into the structure of the canvas, into the way that the canvas may have been primed and mounted, and into the relationships between different canvases by the same artist. For example, when the pattern of the weave of one canvas matches the pattern of the weave in another canvas, this provides evidence that the two have been manufactured from the same loom on the same bolt of cloth. This demonstrates that the two canvases were in close physical proximity and may be interpreted as evidence that the paintings were made at about the same time and by the same artist (or at least by the same workshop). In recent work, density maps have been used to reveal striped patterns that can be used to identify rollmate candidates1 and they have proven helpful in Vermeer studies in issues of authentication and dating, and in the identification of pendant pairs.2
The thread angle maps provide a means of evaluating the presence and degree of cusping along the edges. This can be useful in ascertaining the way the canvas was prepared as well as changes in format that a painting may have undergone.3 Some angle maps reveal thin horizontal or vertical bands (but not both) of modestly wiggling angle fluctuations not near the edges of the painting that traverse the fabric. These features can be associated with the weft threads, thereby providing support for a warp-weft orientation designation.4
This chapter mines our collection of weave maps (generated by the software of the previous chapter) of all of Vermeer’s paintings on canvas for weave density pattern matches, cusping, and weft ‘snakes’.5 The intent here is to illustrate how to go about hunting for weave matches, cusping patterns, and weft snake indicators, rather than to exhaustively catalogue all instances of each of these canvas features from our dataset of stitched X-radiographs of all 34 of Vermeer’s paintings on canvas. That is a thrill we leave to the readers.
Fifth Weave Match Pair Among Vermeer’s Paintings on Canvas: Horizontal thread weave density maps of Woman with a Pearl Necklace (left) and Woman Holding a Balance (right).
1 C.R. Johnson Jr., E. Hendriks, P. Noble, and M. Franken, ‘Advances in Computer-Assisted Canvas Examination: Thread Counting Algorithms’, 37th Annual Meeting of American Institute for Conservation of Historic and Artistic Works, Los Angeles, May 19-22, 2009 and E. Hendriks, D.H. Johnson, and C.R. Johnson Jr., ‘Interpreting Canvas Weave Matches’, Art Matters 5 (2013), pp. 53-61.
2 W. Liedtke, C.R. Johnson Jr., and D.H. Johnson, ‘Canvas Matches in Vermeer: A Case Study in the Computer Analysis of Fabric Supports’, Metropolitan Museum Journal 47 (2012), pp. 101-108 and C.R. Johnson Jr., and W.A. Sethares, ‘Canvas Weave Match Supports Designation of Vermeer’s Geographer and Astronomer as a Pendant Pair’, Journal of Historians of Netherlandish Art 9 (2017), issue 1, http://jhna.org/index.php/vol-9-1-2017/348-johnson-sethares (DOI: 10.5092/jhna.2017.9.1.17).
3 P. Noble, A. van Loon, C.R. Johnson Jr., and D.H. Johnson, ‘Technical Investigation of Rembrandt and/or Studio of Saul and David, c. 1660, from the Collection of the Mauritshuis’, ICOM Committee for Conservation, 16th Triennial Meeting, Lisbon, Portugal, September 26-30, 2011.
4 C.R. Johnson, Jr., D.H. Johnson, I. Verslype, R. Lugtigheid, and R.G. Erdmann, ‘Detecting Weft Snakes’, Art Matters 5 (2013), pp. 48-52.
5 William A. Sethares, 'Automated Creation of Weave Maps’, in: C.R. Johnson Jr. (ed.), Counting Vermeer: Using Weave Maps to Study Vermeer's Canvases, RKD Studies, The Hague (RKD) 2017, chapter 5.