Water transfer printing primarily involves 5 components: primer, basecoat, printed hydrographic film, activator, and finish.
Primer
As with any painting process, all objects need to be cleaned before primer. Depending on the material (wood, plastic, metal), the object may need to be sanded and smoothed. Once ready, a primer (usually epoxy based) is applied to the object. The primer or undercoat will allow the basecoat paint to stick well.
Base Coat
The base coat or top coat is a layer of paint that covers the entire surface to be printed. It is usually white so as to allow all the colors of the design to be visible. With basic knowledge of color theory, base coat colors can be played with. For example, tan base coats are commonly used for camouflage prints because white would appear glaring.
Hydrographic Film
The film is a PVA (polyvinyl alcohol) sheet, which is a clear, water-soluble, synthetic. The design is printed onto the sheet by gravure printing. Rotogravure/gravure is an intaglio printing technique in which a surface is cut into to form the desired image (intaglio), and here it is a cylinder that is the surface. The cylinder rotates against another cylinder and prints designs onto the material in between. The material here is a PVA film, and designs of any complexity are printable.
While gravure printing is used to produce a certain design in bulk, for the advanced home user digital printing is possible. In fact any design can be printed onto blank hydrographic film using a standard inkjet printer with its stock inks
Activator
The activator is a chemical (usually a mixture of xylene and methyl acetate) that softens the film allowing the inks to float on the water. It’s also activated as the binding agent, ensuring adhesion of the ink to the immersed object. Spraying the right amount of activator evenly is crucial as too much or too little will mess up the transfer.
Finish / Top Coat
Once the object is out of water, it is allowed to dry, and then sprayed with a clear coat. This may be either glossy or matte according to preference. It seals the design in and protects it from all kinds of damage.