Paint Curing: Turning New Auto Paint into a Long-Lasting Finish
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Paint Curing: Turning New Auto Paint into a Long-Lasting Finish

There’s a lot of confusion when it comes to drying and curing automotive paint. What does it mean when paint is soft? Does the car go into an oven after it’s painted? How long do you have to wait before you can wash and wax your car after it’s repainted? Here’s what actually happens when you get a full auto body paint job, and what you can do to make sure it lasts.

Drying vs. Curing

Automotive paint is mixed with a solvent, then sprayed onto the vehicle. As the solvent evaporates, it leaves behind only the paint. Once the solvent is gone, the paint is dry. During the painting process, each layer is “flashed,” drying it just enough to apply the next coat of paint.

Curing is the process of polymerizing the paint. The molecules that make up the paint bond together, making them stronger. Soft paint is paint that is dry but hasn’t cured. At this stage, it’s easy to damage.

On its own, the paint can take weeks to polymerize. However, adding a catalyst can speed up the process. Called a “hardener,” this chemical acts as a go-between for the chemical reaction, linking together paint molecules faster than they would on their own.

Baking Paint

Shops used to speed up drying and curing by placing cars in giant ovens. This process could take a couple days as the vehicle is slowly warmed and cooled. Today, the industry has largely switched to infrared (IR) lamps. This light is just outside the visible spectrum, and we feel it as heat. By shining an IR lamp on a freshly painted panel, the paint can be heated from the inside out. This drives out solvents and speeds up chemical reactions. There are three main benefits to these lamps:

– By heating every paint layer at the same time, the paint job cures quickly and evenly. This is especially important for new paint formulations that use water as a solvent. What once took days now takes a few hours.

– There’s no air circulation needed to heat the panel, decreasing the chance of runs and other paint defects.

– These lamps save energy because they’re only applying heat to painted panels. This is good for the environment and lowers the cost of the paint job.

Is an IR lamp just a heat lamp, like the kind you see warming food at fast food restaurants and buffets? Yes and no. Both types of lamps output infrared light, but the type of light is different. Foodservice lamps output long wavelength IR light, which heats the surface of objects. Using a long wavelength lamp will dry the outer layer before deeper paint layers. This causes the paint to buckle, forming craters. Paint curing lights use short or medium wavelength light, which can penetrate surfaces, heating the entire paint job at once from primer to clear coat.

The technician must balance speed and area to finish the paint without causing defects. The shorter the wavelength is, the faster the IR light will penetrate the surface. Medium wavelength lamps are used on large areas like resprayed panels. If there was just a spot repair, a short wavelength lamps can be used to dry and cure the repainted area rapidly. Depending on the type of paint, drying times usually range from 10 to 60 minutes.

When Can I Wash and Wax New Paint?

When the body shop is painting your car, their goal is to get the job completed as soon as possible so you can have your vehicle back. Depending on the paint formulation, the technicians can sand and polish the paint job after anywhere from a day to just a couple hours after the final layer of paint goes on. This means it’s safe to wash and polish your car as soon as you get it. However, the paint isn’t 100% cured.

Most car care products, including polishes and soaps, are safe to use on a newly painted car. In fact, it’s a good idea to keep a spray detailer or waterless wash on hand to remove bird droppings and other debris as soon as they land on your car. Until the paint is fully hardened, it’s more susceptible to damage from acids and dirt.

Waxes should not be used on new paint. They contain UV protectants that can interfere with the curing process. For most paint jobs, you should wait at least two months before applying wax.

When Accidents Happen, You Need Merton Auto Body

There’s a reason Merton Auto Body is the preferred auto body shop for most insurance companies: we’re able to deliver quality work with short repair times, so you can be back on the road as soon as possible. Our shop is in Sussex, just a short drive from Pewaukee, North Lake, Hartland and anywhere else in Waukesha County and the Lake Country area.


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