Clear Lacquers - 1K and 2K
A choice between an air drying lacquer (1K) or one which needs an activator to harden it (2K).
Air drying single pack and two-pack lacquers are used as the final coating for basecoats, not only to protect the basecoat but also to provide the glossy surface required. The advantages are a much higher gloss than is normally achieved with single layer metallics, better protection from weathering and pollution, and a harder wearing surface. Providing dust has not been a major problem in the underlying basecoat, it also presents a surface suitable for flatting and compounding to remove small surface defects and produce a mirror finish.
Single pack lacquers (1K) are (usually) supplied ready thinned, ready for use. Drying times are fast, like cellulose, which makes them ideal for smaller repairs. They are usually acrylic materials, and whilst application is very similar to cellulose paints, it is actually an entirely different material. Do not be tempted to mix acrylic clear lacquer or paints with any other cellulose paint or basecoat - it will either 'curdle' immediately on mixing, or crack in a spectacular fashion when it dries!!
Application is by three to five normal wet coats with adequate flash-off times between each coat. A balance needs to be struck between enough applied lacquer to allow for polishing and protection, and not too many coats, which leads to cracking and crazing with these products. Check the suppliers data sheets for the recommended thickness.
Two-pack lacquers (2K) are much more resilient but have their own application problems due to a) slower drying times and b) poisonous fumes. Even so, they are the preferred material for most repair shops.
They are often based on the same resins as 2 pack paints, hence their much increased weather and chemical resistance compared to air drying lacquers.
When activated and thinned as directed, application is usually by two or three normal wet coats with recommended flash-off times between each coat. Most types will be touch dry within half and hour, and hard dry overnight (16hrs) at temperatures around 20c.
Some lacquers are also available in 'high solids' versions. These are intended to achieve the same film thickness as normal 2K lacquer but using only one or two coats, hence saving time.
As there are so many different but similar products to choose from, always ask for the product information sheet for your particular product. This will ensure that you mix and apply the material correctly - for example some lacquers may be mixed 2:1:1 with activator and thinners, some may be 3:1 lacquer/activator and no thinners (e.g. high solids) and multiple permutations in between, so checking the material 'spec sheet' may save expensive and time consuming rectification work !