Dots and spots: mathematical analysis of katagami patterns

We have always known that the katagami stencils in MoDA’s collections are remarkable.  Mathematical analysis by Alice Humphrey is beginning to reveal more about just how extraordinary they are.

Alice is undertaking a mathematical analysis of the katagami in MoDA’s collection.  More specifically she is looking at the creation of shaded effects by means of differently spaced dots or ‘tonal gradation patterning’.  Alice is using  tonal analysis techniques to identify and count each separate cut element in each katagami.  Alice has found that several of the katagami with fine dot patterning created by punches or drills have have over 16,000 separate cut elements!

Preliminary results

Alice has been analysing the overall tonal range of the katagami using the software package ImageJ.  She uses this to identify the proportion of the designs that would be pigmented on the fabric if it were dyed.  Her analysis has shown that there is a heavy preponderance towards dark designs, with 61% of the katagami being over 90% pigmented.  This possibly has a practical element in that lighter (less pigmented) designs imply more cut out elements.  Therefore the katagami required to print them are more fragile and are less likely to have survived.  But this finding also accords with the Japanese aesthetics of restraint in the Edo period.

Alice has identified seven main categories of tonal gradation patterning on the basis of size, density and layout. She has also started to analyse the dot patterning types by looking at average dot area and range; spacing; and the arrangement of the patterning.

As yet no clear trends have emerged in these data, but Alice is using the dot arrangement patterns to inform the development of the pattern generation aspect of the project.  She will carry out further analysis of the other patterning categories and this will lead into development of associated pattern generation protocols.

Next steps

Over the coming year Alice will continue with quantitative analysis of the katagami.  She aims to see whether this data can be correlated with the use of the designs for particular types or qualities of traditional Japanese garments.


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