Knots and Knotwork - Mathematics and the Liberal Arts

Knots and Knotwork - Mathematics and the Liberal Arts

To expand search, see Art. Laterally related topics: Symmetry, Perspective, Fractals in Art, Weaving, Renaissance Art, Basket Making, Tattoos, Pottery, Pattern, Architecture, Proportion and the Golden Ratio, Metal Work, Wood Carving, Bronzework, Needlework, Art History, Origami, and Mazes.

The Mathematics and the Liberal Arts pages are intended to be a resource for student research projects and for teachers interested in using the history of mathematics in their courses. Many pages focus on ethnomathematics and in the connections between mathematics and other disciplines. The notes in these pages are intended as much to evoke ideas as to indicate what the books and articles are about. They are not intended as reviews. However, some items have been reviewed in Mathematical Reviews, published by The American Mathematical Society. When the mathematical review (MR) number and reviewer are known to the author of these pages, they are given as part of the bibliographic citation. Subscribing institutions can access the more recent MR reviews online through MathSciNet.


Cromwell, Peter R. Celtic knotwork: mathematical art. Math. Intelligencer 15 (1993), no. 1, 36--47. SC: 01A07 (00A69), MR: 1 199 275.

Cromwell discusses a theory for the construction of Celtic knot friezes. These knot patterns may have been inspired by basketry (or maybe by textiles). He then analyzes the patterns in the knot friezes using a notion of a two-sided frieze pattern. There turn out to be 31 such patterns; 7 of these are the standard monochromatic strip patterns; 17 are exactly analogous to the bichromatic strip patterns; and 7 are like the monochromatic strip patterns but require the two sides to be identical. These last 7 "grey" patterns can't occur in knotwork, since the two sides of a crossing are not identical. Of the 24 monochromatic and bichromatic patterns, 12 cannot occur in Celtic knotwork because they would require strings that don't tie up, and 2 require a string straight through the centerline (and also don't occur). The other 10 can theoretically appear. Of these 10, two do not seem to occur at all, and one occurs but with an apparently different constriction technique (an example of this type is thought to be Scandinavian). The author is able to explain the rareness of these symmetry types in terms of the theory for their construction and from the fact that Celtic know friezes were generally finite and had their ends knotted together; these constraints require construction with an even grid, and the three problematic patterns require construction with an odd grid. This explains the type which does occur appears to use a different construction technique. In fact, the author found only one Celtic pattern that uses an odd grid. (And of course it can't be used in a bounded way, though it can be used in a kind of border.) All 7 of the monochromatic frieze patterns were apparently used in generating the existing know patterns, assuming the theory of construction is true (the author makes no claims that it is). The author includes examples of his own for the 3 problematic odd-grid know patterns. Excellent article. The author includes a good bibliography of related topics. It goes as far as Norwegian peasant art, for example. Not inordinately technical, in spite of the way it might sound. Closely related topics: The Celts, Two Sided Frieze Patterns, Frieze Patterns, Bichromatic Strip Patterns, Weaving, and Basket Making.

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Grünbaum, Branko; Shephard G. C. Interlace patterns in Islamic and Moorish art. The Visual Mind, 147--155, Leonardo Book Series, MIT Press, Cambridge, Mass., 1993.

Many Islamic and Moorish patterns exhibit what the authors call interlace patterns, where the patterns seem to be made of strands that alternately go over and other strands. This is a phenomenon that makes these Islamic artworks appear something like a 2-D extension of the Celtic knot friezes; the over/under rule is of course also common in weaving. The authors focus on the seemingly curious phenomenon that many of the Moorish and Islamic interlace patterns can be viewed as being made of a small number of basic shapes, often one or two. The authors analyze this phenomenon for the symmetry groups p4m and p6m, and find that it arises in a mathematically natural way, especially if artists used stencils, as is sometimes now thought. The article gives give propositions without proof; proofs of these should be within reach of a good undergraduate with the requisite knowledge of group theory. Closely related topics: The Islamic World, Plane Patterns, and Weaving.

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