Instructions for substrate preparation before painting

A complex topic.

Background and grayscale surfaces.

Of course, to get the tone right, we need to be aware that the base color also has to do with the finished shade. First of all, it’s quite theoretical and I hope to give you a little help here.

The simplest example of choosing a filler color is the shade white.

Would you go with a black background on instinct? Surely not, right? It’s such a logical feeling. Black is much darker than white.

Unfortunately, you see it time and again that completely wrong background tones are used for the main color tone. The problem in the whole paint structure, which in this part refers for the time being to car painting, is called translucency (sth. is translucent).

Translucent means that material is translucent. A good example of this is frosted glass. You can’t see through it, but the light passes through. This is also how today’s paint materials work. NOT with all color tones or paint groups, but I do not want to discuss that here. The point here is to understand the nature of the substrate.

Very theoretical. Yes, I know. But it has to be.

If you imagine you had to paint a red component now. Would the substrate then be rather light or dark? – Hm, that’s where it starts. It depends. Is it a bright red, or a more dark Bordeaux red?

Color coating is about complex interactions of material translucence, light absorption, and reflection. At this point, a translucent material needs a certain background tone that makes the color glow or lets it „sink in“ a bit. And here we are walking on a knife-edge.
The wrongly chosen base „pushes“ the color tone in the direction where it should not go. It’s not about the 10% or 20% gray part here. At this point, it’s about whether you just take what’s there, or wait and get a different right base tone.

So a bright red needs a lighter tone and a Bordeaux needs a darker undertone.

As a rule, we are talking about four to seven shades of gray (seven if you count the base tones, black, gray, and white). But even here, paint manufacturers disagree. The shades of gray are mixed according to a certain formula, and some of them are predetermined to the corresponding color tone in the car refinish paint. A white in the underground occurs pretty much never, to not at all, no also with white rather rarely. Here, in fact, rather a very light gray is used.

So how do I get the best background color?
Here one can orient oneself however very well at the Grey-Shade-Identifier system of the mark BASF (NO advertisement!). There may be similar systems from other manufacturers, but this one is already very accurate. By stopping the gray scale you can immediately see in which direction of the gray scale I should move.

A fellow technician said a good phrase to me at the time, „Color, how are you?“ at this point, thanks for that. That sticks!

In fact, there are answers. Namely, color characteristics. Light, dark, rich, pale, green, yellow, etc.

With this knowledge, the next background determination should be a bit easier after all.

Filler grinding and voids

At this point, I would like to point out possible substrate defects.

Depending on the material to be used, you can create certain roughnesses and paint on them without seeing sanding marks afterward. Here again, the recommendations differ from manufacturer to manufacturer. Therefore, the preparation before painting is elementary important and should be thoroughly checked. Here is more on the subject of sanding.

Even small shrinkage marks, which are perceived as small holes in the surface, become disturbing factors if they are not removed.

How to deal with them you can find HERE.

Surface cleaning before painting

Another important point is cleaning. If grinding residues or grease are left behind by fingerprints or handprints, this can lead to coating damage or adhesion problems.

You can find more information about cleaning here

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