ABSTRACT This paper discusses the mechanical interactions between a magnet and a thin paint layer situated on a non-magnetic substrate, for example, to correct painting deformations or to fix pictorial layers. Crucial to calculating the attraction force F is knowing the magnetic susceptibility χ in the paint layer center XC and also the gradient dH/dx across the paint (calculated from magnetic fields H on both sides XS and XE of the layer). However, the susceptibility χ depends on the magnetic field H which is a function of the distance from the magnet’s pole: χ = f(H(XC)). It should be noted that as the magnet approaches the paint layer, the value of the field H(x) increases, but the susceptibility of the substance χ(H(x)) decreases. Analytical formulas and practical calculation schemes for mechanical forces in the discussed magnetic systems are presented in detail. As a result of the undertaken work, interactive on-line calculators for calculating magnetic fields and forces were developed and made available online. Reliable estimation of mechanical forces due to magnets, as presented here, allows for more controlled and reproducible conservation results. Therefore, the principle of minimal intervention and reversibility can be attained repeatably with greater ease, laying the groundwork for improved protocols.
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