Fellow Shadow Watchers Further to John Bercovitz' encyclopedic response on fixing metal numerals to stone just one word of warning, born of recent hard experince, for anyone using silicone adhesives to secure metal dials to stone.
The alignment had gone ultra-smoothly with Mac Oglesby and his wife Claire helping to align the dial and photograph the event. Six hands were certainly better than two when the sun was only glimpsed for a few vital seconds and two marks needed aligning simultaneously. The dial is in a public place so, to deter the curious until the silicone had cured, a black plastic sheet was secured in a small 'tent' over the whole assembly. The gnomon is the main mode of fixing and a 'tenon' on the underside of the dial with 'retaining pegs' continues down into a deep cavity filled with quickset mortar. A thick bed of silicone filling the gap between three levelling screws and the actual plate was supplementary to this. Is it ammonia that silicone gives off when it is curing? It certainly did a good job of prematurely 'patinating' a large bright brass dial. Perhaps sacking instead of sheet plastic would have avoided this. Fortunately the ugly patination is superficial and easily dealt with but what a disappointment for the clients when the protective sheeting was removed! Tony Moss
