A thicker layer of coating is meaningless to 99 percent of the population. What is truly the point of a thicker layer of coating?
It comes down to coating density. I'm gonna use CQuartz UK as an example. It has multiple siloxane forms in the blend, and they chain together in the resin itself. That means that usually Cquartz UK bonds at a 1.5 micron level because the layer was resin was designed to hold its siloxane blend. Now, you let it cure, then put on your second layer. You might get to an even 2 micron level. Why? Because when you try to apply the second layer, the resin layer itself (responsible for the thickness) won't create a second layer on top. Instead, it'll just deposit the siloxane layer ontop of the resin that's already there. There's still bonding agents so it'll still drop into the resin. But the rest of the resin won't be there, because you wiped it off. Why? Because that layer of resin has no clearcoat to set onto. A coating surface is not the same as clearcoat. The clearcoat will cause a chemical reaction, the coating surface will not. So what happens when you do a third layer? Nothing really. You might be at 2.1 micron or 2.2. There's only so much siloxane components that layer of resin can hold.
When you take Gyeon Mohs and you put on one layer, there's a certain amount of protection agent in the resin. When you do the second layer, it'll add more protection agent in the resin. When you do the third layer, same thing. But if you try to do a fourth layer, the resin itself has no more room for more protection agent. When coating products talk about layerability, this is what's actually happening. You're making the one layer of resin on your paint more concentrated with protective agents.
When products are not layerable, it generally means that the coating already has the maximum density of protection agents the resin can hold. You can go ahead and add as many layers as you want, it just won't do anything. Whatever you put on in the second layer will be on your towel afterwards after the wipe off.
The thickness and layerability of coatings is a very minute factor in their effectiveness.
Using the worst version of layerability, Ceramic Pro. It's individual applications are super easy to apply, and yet you need like 4 layers. You basically apply to an entire panel and then wipe off. Then you do your other 3 layers to add enough Siloxane components into the resin that it becomes actually durable.
Optimum Pro+ (whatever the two layer one is called)
You have to add the second layer in during a specific time frame because the top layer is inducing a specific chemical reaction with the bottom layer because their coatings are SiC based. Once you're past that window, the bottom layer has cured and will not accept a chemical reaction. The way that coating works is one layer goes in, then second layer goes in. The two layers then combine to create a chemical reaction to form a different base element than what was put on.
Again, coating thickness only matters to 1 percent of those who use coatings and only if they understand what the point of it is.
