What Causes Spray Paint to Crack?

Randy Charles
Professional Painter

Randy Charles is the owner of PaintCentric.com, a website dedicated to providing information, tips, tricks, and news about all things paint. With over 10 years...Read more

Spray painting, whether with a can or a sprayer, is a quick way to revamp almost anything, from old pieces of furniture to crafts, and gives it new life. It is easier to get paint into all of the small crevices when you spray it. But in reality, you may encounter various issues with getting an even finish that is free from cracks.

The primary reason why spray paint crackles are humidity or moisture. With increased humidity, the surface to be painted would be wet, and this wet surface affects how it sticks to the surface. At this point, the paint ends up cracking.

This article will expose you to some other factors that contribute to painting crackling and how to avoid them so you can have a successful project.

Spray Paint Cracking on Different Surfaces

One of the reasons spray painting is so widespread is because it can be easily used on all sorts of surfaces. These include ceramics, concrete blocks, mirrors, glass, wood, plastic, or metals. But with each surface comes slightly distinct rules.

On Metal

A common surface for the application of spray paints is metal. However, paint does not adhere well here because metals are prone to extremely cold temperatures. The solution is to warm up the metal surface with a heater, after which spray paint can take effect without a primer. If not heated up, the paint will fail to stick.

Now before you paint, preparing the surface is just as essential as spraying it. For the paint to go as evenly and smoothly as possible:

  • Ensure the surface is smooth
  • Use a primer if the metal is rusty.

Cleaning with a wet cloth, removing loose paint, and sanding down the surface are good practices to ensure better paint application. Don’t fail to ensure that the previous layer is fully dry before applying another.

On Wood

Like any material, wood needs preparatory steps before the spray paint application. If the wood surface was previously painted, it will not accept paint until the current finish is removed. And to have fewer adhesion issues, you may need to prime first.

Spray Paint Crack On Wood

For bare wood, yes, priming is necessary. Bare wood is highly absorbent, so the primer gives a solid base coat. More often than not, without it, the wood will crackle. Also, if it isn’t a smooth surface, sand it properly. The smoother the area you’ll be spraying on, the better your results will be.

Choosing the right spray paint is also essential because not all spray paints work well on wood. So you want to select a product that can specifically handle wood surfaces.

On Plastic

The plastic market is significant because plastics are mainly used for home crafts. This means the shapes can be complicated and multi-surfaced, making spray painting a tough project.

When you spray paint plastic, it has a high probability of cracking when it starts drying. Hence, you will need to apply the paint from multiple angles to accomplish a finished job.

Spray Paint Crack On Plastic

But again, this makes layering excess paint too quickly, leading to crackling in the spaces where paint application overlaps. To prevent this:

  • Ensure you wait long enough before the next coat (between two different angles likely to overlap).
  • Do not apply the spray paint in multiple layers. Wait until the previous layer dries before applying another.
  • Begin by sanding the plastic and degreasing it. Oil on the plastic will deter paint adhesion.
  • Next, prime the surface with the primer of your choice. Only start spray painting after the primer is dried.

On Glass

Glass comes in different types, some of which are easier to paint with spray paint than others. The commonly used types to paint over are the simple sheet of regular glass or the decorative glass piece (stained glass).

And with diverse spray paint types, it is paramount to remember the type of paint to use and apply correctly. Using the paint made for glass is good practice if you can afford it.

Spray Paint Crack On Glass

Spray painting glass is effortless as it presents with an already smooth surface. Hence, primers are not always necessary. When excess paint is used, the top layer dries before the bottom, resulting in spray paint crackling on glass.

Similar to plastic, spray painting a vase or any curved object requires difficult angles, and cracking may occur if excess paint is concentrated at a spot. Again, dry the surface before spraying.

Why Does Spray Paint Crackle?

It can be quite frustrating when you’ve completed spray painting, only to look closer at it and notice crackling across part of the surface. Cracking (also known as webbing) is more likely to occur with a reaction between the paint layers or when the first paint coat doesn’t completely dry before you applied the second coat (irrespective of the primer, base coat, or topcoat).

Why Does Spray Paint Crackle

Just like poor surface preparation and temperature, other factors contribute to painting crackling.

The Thick Layering of Paint: Crackling occurs when the paint is thicker than usual, maybe as a result of prior layering. The best fix is to apply a fresh coat of paint each time and to paint with a thin layer.

To get a thin layer, the recommended spray technique is to hold the can 12 to 18 inches away from the work surface, spray and then quickly stop. The new goal would then become to have the paint dry between layers.

Applying excess paint is not the right way. The top layer will take longer to dry than the bottom, and this top layer will sink into the old one and won’t adhere. This yields an uneven application and makes the paint crackle. So instead of going for heavy coats, go for multiple lighter coats.

Humidity or Moisture: During the hot months, when the paint dries, the layer of paint becomes very brittle, and it cracks as a result of moisture evaporating from the paint.

When top layers need more time to dry than the underlying layers, it causes a high degree of moisture on the surface and can also lead to cracking.

Mixing: Mixing paints can lead to crackling when they don’t combine properly. They dry and move differently within the layer.

How to Fix Spray Paint Crackle?

Step 1: Sanding the surface

Use medium-grit sandpaper and gently scrub away the uneven bits of paint. The goal is for a smooth surface, so rub gently so as not to scrape off all of the previous paint, but only the top crackle.

Work in small circular motions. Bend the sandpaper to fit it into small crevasses and holes. For wood, smooth out the rough edges and splintery areas. For plastic, scuff the surface enough that it will take the paint better.

Step 2: Clean the Object

All that dust and powdered paint from the sanding will prevent the paint from sticking. Using a paintbrush or tack cloth, dust away all debris and loose dirt from the object.

For a little extra, apply a damp cloth to wipe the surface after dusting. This will ensure that there’s no powdered paint left on the object but ensure the object dries completely.

Step 3: Prime the Surface

After cleaning, seize the primer of your choice. Using the paintbrush, paint a thin layer of latex primer on the object’s surface as evenly as possible. Do not be tempted to apply a second coat of primer before the first one dries.

It’s okay if the first layer doesn’t conceal everything; the second layer will do the job. Allow the primer to dry for at least 5-7 hours. Latex primer prepares the object’s surface to accept spray paint more readily.

Step 4: Sanding the surface Again!

Sanding the primed surface gently will give you the smoothest possible base possible. Now, taking these few extra minutes will make your paint last much longer. Don’t forget to clean the surface afterwards, as previously mentioned.

Step 5: Apply the First Layer of Paint

Apply a new coat of spray paint. Be sure to aim for a light coat using the 12 inches recommended technique as a spray. The goal is to paint it as evenly as possible. After that, allow the paint to sit for 3-5 hours.

Step 6: Apply the Final Coat

Apply a second and final coat as lightly as possible. Aim for any patchy bits which the first layer did not conceal. Allow the paint to dry for another 4 hours, and you’re set! If you find a few remaining patches, you can spritz them with the paint.

How Do You Paint Over Cracked Paint?

In a well-decorated area, cracked paint may be a real eyesore, and you don’t have to live in such a state of affairs. Here are a few restoration methods:

  • Brush down the entire surface area of the space after you’ve sanded it. It’s imperative that you thoroughly brush away all the dust. Apply a single coat of high-grade undercoat with a roller or paintbrush. Make clean, uniform strokes when applying the paint.
  • Allow the undercoat to dry for about 24 hours. Finally, surfaces primed with quality latex paints can be applied with fresh coats.

Final Thoughts

Today, both crafters and professional house painters use spray paint. Spray painting crackle can be, in most cases, quite easy to fix. It is more hassle and better to avoid it, but no need to panic if you notice a crackle. In all these tips, the best way to achieve the ultimate finish is all in preparation.

Randy CharlesProfessional Painter

Randy Charles is the owner of PaintCentric.com, a website dedicated to providing information, tips, tricks, and news about all things paint. With over 10 years of experience in the painting industry, Randy has become an expert in the field and is passionate about helping others learn more about painting. He has written numerous articles on the subject and is committed to providing accurate and up-to-date information to his readers.

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