Hi, It sounds an interesting project.
If you must use wood, don’t use exterior grade ply. Exterior grade ply specifications relate mainly (possibly only) to the glue that is used; not to the way they might survive in an exterior environment. Marine grade ply is much better – the more so if you go for Bruynzeel Marine Plywood, at least 18mm thick; though it is not not cheap and may cost you over £200 just for your one panel. You should choose grades that are compliant with either: Suprahecht® - Lloyds register type approval certificate No. 04/00049 (E1) Hechthout® - Lloyds register type approval certificate No. 04/00047 (E2) They can be expected to last 10 years, possibly even 20 years. This will probably be longer than the lifetime of the paint. Always use exterior grade paints – certainly not any artistic paints, even if the colour range is limited and be sure to paint the back as well as the fronts and most importantly the sides. Indeed it may be sensible to seal a strip of lead around all the edges too. Such a dial may last 10 years or possibly more. You might also consider using stainless steel sheet as the backing. This can be powder coated and baked with its background colour before applying oil based paints of exterior grade or, of course – and more difficult and expensive , you can use a computerised approach to powder coat the dial itself on the steel sheet and bake that. This would last decades. A resin coated approach might work too. Regards Patrick From: Jackie Jones Sent: Friday, May 08, 2015 5:46 PM To: [email protected] Subject: Painted dial Dear All, I have been asked to do a painted dial for a south facing wall. Due to lots of reasons, I am going to paint it on board and then screw it onto the wall when it is completed. The wall is not suitable to paint directly onto and it is some distance away from me. I thought of using exterior or marine grade plywood; has anyone who has had any experience of this any tips or advice as to how to protect it so it will last a good number of years? Should I also paint the back and/or cover the top edge of the wood? Many thanks, Jackie Jackie Jones 50° 50’ 09” N 0° 07’ 40” W -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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