Nitrocellulose and synthetic lacquers are by far the commonest finishes in industry, because of their fast application and drying. There are brushing varieties, which are thicker and slower-drying for even ‘flowing on’, but generally spraying is best. You can cover large areas in a very short time and, with careful and thorough rubbing down between coats, achieve a superbly smooth finish quite easily.
These materials take between 30 and 60 minutes to dry reasonably hard, and many can be recoated after that time; full curing takes at least a day, and in some cases a week, after which they are among the hardest and most durable of all finishes.
Cellulose is made from nitro-cellulose, resins, plasti-cizers and thinners; pre-catalysed lacquers include cellulose, melamine, and acid hardeners, but the synthetic resin-carrying and acid-catalysed lacquers, the toughest of all, need to be mixed with a hardening catalyst immediately before application.
Cellulose finishes offer no advantages over pre- or acid-catalysed lacquers, apart from a certain extra flexibility allowing movement of the wood. They all come in satin, matt or gloss finishes, and should be used with water-based stains and fillers, or ones that use the same solvents as the lacquers themselves. Like spirit-based products, nitro-stains and fillers are easy to use and mix. If you do use oil- or spirit-based stains and fillers, seal them well with at least two coats of the lacquer you use; and wait and watch for a possible reaction or bleeding through. Avoid laying these lacquers over shellac or varnish.
Lacquers can be tinted with their own colours, or you can use cellulose-based enamels for car touch-up work underneath them.
The hardness of these products, particularly acid-catalysed lacquers, makes them ideal for ordinary household use. They are resistant to mild acids and alkalis and stand up to knocks and heat very well – although damp heat like steam corrupts pre-catalysed lacquers fairly easily.