All you need to know about wet-on-wet Primer

What is a wet-on-wet primer?

A wet-on-wet primer is a type of primer specially formulated for wet-on-wet application. It is a very fine filler primer that does not require sanding or complete drying before painting. It is designed to :

• Create an adhesion layer between the substrate and the paint
• Insulate the surface properly
• Offer a smooth finish that can be directly overpainted with the base or finish.
• It is more fluid than a conventional filling primer
• Its insulating and adhesion properties are optimised by the finish
• It dries quickly on the surface, allowing the next coat to be applied after a period of evaporation.

The wet-on-wet primer can be applied to new parts such as cataphoretic sheet metal or primed plastics. It is also ideal for quick repairs where there are no major defects to repair.

What types of surface can be treated?

A wet-on-wet primer is a versatile product for bodywork workshops, but is only suitable for clean, sound and even surfaces. A number of surfaces are suitable for priming: cataphoretic sheet metal, aluminium or steel properly prepared with an anti-corrosion primer, plastics such as bumpers or mouldings, and old, well-adhering paintwork.

How do I achieve good adhesion?

To achieve good adhesion with a wet-on-wet primer, the surface must be clean, slightly rough and free of grease. The product clings poorly to a smooth, greasy or dusty surface. That's why old paintwork or new parts are lightly sanded and carefully degreased. The primer itself should be applied with the correct Mixing ratio (Hardener and Thinner) and in even coats, neither too thin nor too heavy, to create a smooth but tacky film. It should be left to evaporate for the time indicated on the technical data sheet, to allow the solvents to come out properly before applying the finish.

What are the risks of wet-on-wet application?

Wet-on-wet application is practical and quick, but you need to be careful, as it involves a number of risks and limitations that it's important to be aware of:

1. Poor adhesion :

If the surface is not perfectly clean or lightly sanded, the Paint may peel or blister.

2. Marks or runs :

Applying too much primer or an uneven coat can result in drips, thick areas or visible spots in the paint.

3. Finishing problems:

Wet-on-wet Primer does not really fill. On surfaces with scratches, dents or blemishes, these imperfections may show through the paint.

4. Sensitivity to conditions :

Temperature too low, high humidity can cause effects like orange peel, i.e. a grainy texture or bubbles in the film.

What are the advantages of wet-on-wet priming?

Wet-on-wet priming has several impact spanners:

1. Considerable time savings:

You gain in productivity in your bodyshop, as you don't need to carry out the Sanding stage between the primer and the paint. Fast drying time means you can go straight to finishing. Generally, wet-on-wet primers can be painted after just 20 minutes drying time.

2. A smooth, even surface :

This type of product provides an even finish for the Topcoat, so there is less risk of dust or micro-scratches from sanding.

3. Easy to apply:

Easier to apply to new or directly repaired parts. It allows you to work on clean, even surfaces without complex intermediate steps.

4. Ideal for light or superficial repairs :

Perfect for surfaces with no major defects, such as new parts or quick Touch up.