Guido,
>after some efforts i have calculated my vertical declining sundial, and it >seems to work fine. >Now I have the problem to draw the final hour lines on the preliminary ones >(drawn with a pencil), but the wall surface has many granules and it is >difficult to obtain sharp edges for these lines. >Could you please help me? Which is the best kind of varnish to be used? >Which is the best technique for lines drawing? Why not define the shape of your intended dial with e.g. 3mm thick strips of wood, possibly fixed to the wall with screws or 'masonry nails', then skim the whole area level with exterior grade plaster or fine mortar rendering? Any good tradesman would do this very quickly. This would also allow you to make sure that the dial face is true vertical by adjusting the thickness of the top and bottom strips with a spirit level in vertical mode. The plaster/rendering could then be painted to blend in with the colour of your wall perhaps. There are fibre-tip 'any surface' pens marketed for indellible marking which claim to be UV light proof. Marks I have made with these on concrete are still there one year later so this may be a start. Alternatively I'd experiment with a 'V' shaped 'hook scraper'* dragged (not pushed) along a metal straightedge held in position against locating pins driven into the temporary wood surround. (Probably best before the plaster is fully cured.) Then carefully fill the lines with paint and a good quality artists' sable brush - again against a straightedge (wooden this time) offset sideways from the line so that it guides the metal 'sleeve' of the brush. Masking tape well rubbed-down either side of the line may help to avoid mistakes. All processes perfected on a 'trial' area before work on the dial itself of course. * JPEG on request Casual thoughts based on how I would approach it. Hope this is some help. Tony Moss. Website: http://lindisun.demon.co.uk
