Understanding the Role of Friction and Adhesion in the Display of Tapestries on Slanted Supports

Abstract

This paper reports on an investigation into slanted support, an increasingly common method of displaying tapestries in mainland Europe. Two factors contribute to the efficacy of slanted supports for tapestry: the angle of display and the degree of friction between the tapestry and the support. Initial analysis demonstrated that a small degree of slope, of 5°, has only marginal impact on reducing the load experienced by the tapestry. Experiments were carried out to compare the friction between small tapestry fragments and a range of fabrics commonly used to cover slanted supports. Lined and unlined tapestry fragments were placed on a fabric-covered board and tilted from horizontal to vertical. In most cases it was found that the board could be tilted beyond vertical before the tapestry began to slip; this meant it was not possible to calculate a coefficient of friction. It was clear that the simple Coulomb model of friction does not apply in this situation and that adhesive forces are even more significant than friction. Loading the tapestry samples demonstrated that the coefficient is dependent on load, confirming this observation. The paper also reports on the use of digital image correlation (DIC) to calculate strain data. A tapestry fragment was suspended on a vertical board half covered in cotton molton fabric. The strain values were very low on the half of the tapestry against the molton; they were higher on the half against the uncovered board. It was also apparent that the tapestry with board-covering fabric was less subject to expansion and contraction caused by fluctuating relative humidity. The research concluded that the friction/adhesion forces are so effective that a tapestry is well supported on a vertical fabric-covered board; there is no additional benefit in providing a small degree of slant.

Investigating mechanical damage mechanisms of tapestries displayed at different angles using 2D DIC

“…For instance, it is thought that some kind of 'adhesion' may take place possibly due to interlocking of fibres or electrostatic interactions between the tapestry and the covering fabric [31]. More details on this series of tests can be found in Lennard et al [32].…”