PAINT Finishing TOUCH

We asked Thames boatbuilder Colin Henwood, who teaches finishing to students at the Boat Building Academy, to give us a crash course in paint and varnish. In this second part, he tackles the subject of a perfect traditional gloss paint finish

- Colin Henwood

Continuing with the more conventional coatings, enamel paint systems work well on solid wood and traditionally constructed boats, they are quite tolerant of poor workshop conditions, the products are not aggressively toxic, and they are straightforward to apply. The surface to be painted will not need the same level of fine sanding as for varnish, but, it must be fair, without any unevenness, and all machine marks and hard edges dealt with. Generally, I will sand to P120 grade abrasive to give a good key for the primer.

From bare wood, the paint system usually consists of primer coatings, undercoat paint, and the gloss enamel coating. The primer layer is an important element in the quest for a long-lasting finish. Primers are designed to stick to wood and provide a stabilising, moisture-resistant foundation for the more cosmetic enamel paint. Manufacturers recommend the number of primer coats required, usually two, with the first coat thinned by a percentage to penetrate the wood. However, primer paint does not flow out to lose the brush marks. So, to achieve a good thick primer layer that can be flatted back to provide a basis for the next stage, apply three coats, with the first thinned as recommended, followed by two full-strength coats, with our quick preparation technique between coats, as described in last month’s varnishing piece. Allow the third coat to harden for a couple of days before abrading it back to a smooth surface with P240-grade abrasive. Dust control is exactly as described in the varnishing piece.