There are two main types of paint used for basecoat, solventbase and waterbase. There is a big difference between the two both legally and application. Of course, waterbased paint is the more environmentally friendly option but does have a few flaws.
solvent based paints are known for fast drying times and is usually mixed 1:1 or 2:1 with a solvent thinner. Some people use a standard thinner commonly known as gun wash thinner (poor quality thinner) which is not recommended. I do always recommend using the same brand thinner as the paint you are using or a good quality well known thinner.
Solvent based paints are often applied incorrectly. Usually when i see problems with solvent paint it is applied at high pressures (above 2 bar) and applied dry or too light coats. Applying the paint this way can cause many issues. Poor coverage, patchy or stripy effect, haloing around metallic blend area are all causes of applying solvent paint incorrectly. Make sure the technical datasheet is followed correctly or speak to a technical rep for the paint company. I usually apply the basecoat quite wet but not too wet that the paint will run or the metallics flakes move. You will get to know how far to push the paint you are using.
solvent based paint generally dries quite fast without any air movement but blowing air onto the paint will speed it up even more. Try not to use hot air guns to dry the basecoat this can cause problems such as boiling the paint and drying a different colour to what it should be. Cold air dries the basecoat just as quick as hot! I usually recommend keeping the booth/room temperature around 22-23 degrees celsius during application but please check the manufacturers TDS sheets.
Things to note:
Solvent basecoat can react easily, more so than waterbased. This is something to watch out for and make sure that the panels to be painted are 100% clean using a good degreaser.
If any reactions happen just allow to dry fully and lightly sand back with a P1000.
Waterbased paints are very different to solvent based. Firstly they are thinned using demineralised water or a type of alcohol depending on the paint brand. Waterbased Paints are usually more resistant to reactions than solvent but takes a lot longer to dry.
Applying waterbased takes a lot of practice to make sure metallics can lay correct and that it doesn't look patchy. A temperature controlled environment is needed for using waterbased paints as it can be quite sensitive to change in environmental conditions
humidity and temperature pays a huge part during application as well as spray gun setup.
waterbased paints do dry better in a warmer environment. using tools such as a venturi blower or a fanjet help dry the basecoat correctly. One main thing to note is to make sure that the basecoat is dry from the ground up. Sometimes waterbased paint can appear to be dry but it is actually still wet underneath. This is a big problem to fix if this happens.
Things to note
The use of a waterbased degreaser is good to use with waterbased paints. Make sure that the waterbased paint is being sprayed in a controlled environment.