The clear coat is polyethylene paint without color pigmentation. Thickness usually ranges between 1.5–2.0 mils (35–50 microns).
The clear coat should be thin but have enough coverage that there are no holes in the layers. Before you spray the clear coat on the exterior, consider practicing first. Grab a piece of scrap metal and test the product and your technique. Also note that clear coats are made of resins, solvents, and additives.
The layer of clearcoat applied is too thick.
While putting less clearcoat may cause a problem within a few weeks or months (not enough UV-absorbers in the film), applying too much clearcoat may lead to matting much faster, especially if drying temperature is higher than advised.
The average basecoat/clearcoat surfaces are 4.0-6.0 mils thick, with the clearcoat being around 2.0 mils. of that. When removing defects in the refinishing material, it is important to monitor how much clearcoat is being removed. If too much is removed, it can cause: hazing, discoloration, peeling, and finish failure.
The thickness of this layer ranges from 38 microns (µm) to 102 microns (µm). Ultimately this tells us the total thickness of the various layers on most modern cars is between 67 microns (µm) and 198 microns (µm).
A Coating/Paint Thickness Gauge is used to measure exactly how thick the layer of clear coat/paint is on the car. Once you know how thick these layers are, you will know how much of the surface you can abrade away without burning through the clear coat or paint.
Polishing minor scratches and swirls removes around 3-10 microns of clear coat a time. A brand new car has a clear coat that's between 40-80 microns thick.
Clear-Coat - The final clear-coat layer is what tops off your car's paint, so you'll need to be careful about the grittiness of the sandpaper of your choice. 1,500 grit is a good starting point, though you'll need to be cautious about sanding it off too much.
The clear coat has a 2:1 mixing ratio with the catalyzer/hardener which is available in Fast (5-15°C), Normal (15-25°C), or Slow(15-25°C) speed. Application : In one light pass (thinning at 5% recommended), followed two minutes after (more or less depending on the temperature) by 1 or 2 wet coats (thinned at 10-20%).
Coming in at only 1.5 – 2 millimeters thick (Thinner than a Post-It Note), clear coats are not very durable and it's even possible to scratch it with your fingernail. Clear coats simply don't offer much protection.
Generally, the clear coat will dry within this time, making your car fit for driving. It takes about 30 days for the clear coat to cure fully, and this time duration can vary based on environmental factors. There are cases where certain types of clear coats cure and harden in less than seven days.
If the finish is not glossy, you may not have applied enough coats, or enough clear coat to flow. There is some technique involved here, as too little clear coat will appear dull, and too much will stand up like a bead of glue and take a long time to dry.
Clear coat finishes are harder and more resistant to oxidation. However they are more sensitive to scratches and you should be careful not to use abrasive rubbing or polishing compounds on them. Although these finishes are also prone to oxidation.
When it comes to applying the final clear coat, after having finished with the paint job, three to four clear coats are generally recommended.
Clear Coat
Just like with the base coat, sanding between coats of the clear coat is not recommended. If there is some imperfection or defects, then sand it down very, very carefully. This is owing to how thin the clear coat is.
Buffing clear coats make scratches and nicks disappear. It also makes the paint job look fresh and new again. However, clear coats will always be prone to damage, and buffing is an excellent way to eliminate any imperfections.
Applying a clear coat to your car is a smart way to preserve it, but sometimes this can go wrong, leaving it with the notorious “orange peel” effect, which requires a wet sand to remove. This process helps restore beauty and shine to give your car maximum appeal.
Incorrect mixing ratio: If too much activator/hardener is used, or if the correct ratio is not properly mixed, defects may appear in the finished dried paint film. Environmental conditions: Excessive heat or humidity during application and curing can cause surface imperfections such as cracking.
Car-Rep® 2K Polyurethane Clear Coat with Wise 2K® Technology is crystal clear, very strong, extremely durable, and forms a chip and UV-resistant film.
1500 to 2000 Grit – When you need to smooth out surface imperfections and scratches before and after applying the clear coat, this is the grit range to use. This will also require the wet sanding technique to prevent clogging the sandpaper.
And since the clear coat is applied on top of the base, most clear coats will easily cover 400 grit scratches.
1,500 – 2,000 Grit
Both grits are great for removing light clear coat scratches that can't be removed by rubbing compound and buffing. Use 2,000 grit for final sanding to achieve smooth surface.
As a rule of thumb for my own cars – I usually limit any kind of harsh polishing (Medium Cut or Above ) to two times per year maximum.
Washing your car thoroughly, including removing embedded contaminants from the clear coat, is necessary prep work for paint restoration. Likewise, waxing your car isn't a restorative measure, but car wax does help to protect your car's paint finish after you've corrected it.
If you over-polish your car, you will eventually thin out the paint and in extreme cases can cut through the clearcoat and the paint right through to the undercoat! The diagram below illustrates various types of paint defects. Polishing removes material from the top layer – in most cases this will be clearcoat.