Why Does Spray Paint Crack? Solutions and Fixes

Spray Paint Crack – Cracking, also known as “crazing” or “alligatoring,” is a common and frustrating problem with spray paint. It happens when the top layer of paint dries too quickly, while the lower layer is still wet. As the bottom layer continues to dry and shrink, it pulls on the rigid top layer, causing it to split and form cracks.

Here’s a breakdown of the common causes and how to prevent and fix them.

Common Causes of Spray Paint Crack

1. Applying Coats Too Thickly

This is the most frequent culprit. When you apply a heavy, single coat of spray paint, the outer surface dries rapidly, forming a hard film. This film traps the solvents and wet paint beneath it. As the inner layers dry and cure at a slower pace, they contract, causing the rigid top layer to break and create a crackled or wrinkled effect.

2. Improper Surface Preparation

Spray paint needs a clean, dry, and properly prepared surface to adhere correctly. If the surface is contaminated with dust, dirt, grease, oil, or old, peeling paint, the new paint will have poor adhesion. When the paint doesn’t bond well to the surface, it’s more likely to crack or peel as it dries.

3. Extreme Environmental Conditions

Temperature and humidity play a significant role in the paint’s drying and curing process.

• High Temperatures: When it’s too hot, the solvents in the paint evaporate too quickly, causing the surface to dry almost instantly. This traps the wet paint underneath, leading to cracking.
• Cold Temperatures: In cold weather, the paint takes much longer to cure. This can also lead to cracking as the paint struggles to dry evenly.
• High Humidity: Excess moisture in the air slows down the drying time. This can cause problems if you apply a second coat too soon, as the trapped moisture and solvents can lead to cracking and poor adhesion.

4. Applying a Second Coat Too Soon

Even if you apply thin coats, rushing the process can ruin your finish. If you apply a new layer of paint before the previous one has fully cured, the solvents in the new paint can “reactivate” or attack the layer below. This can cause the paint to lift, wrinkle, or crack. It’s crucial to follow the manufacturer’s recommended drying and recoat times, which are typically listed on the spray can.

5. Spray Paint Crack Product Incompatibility

Using different types of primers, paints, and clear coats from various brands or product lines can sometimes lead to chemical reactions. For example, applying a lacquer-based clear coat over a fresh enamel paint can cause it to crackle because the strong solvents in the lacquer dissolve the enamel beneath it. It’s always best to use products from the same brand and follow their recommended system.

When a spray paint job cracks, it can be frustrating, but don’t worry—it’s usually a fixable problem. The solution involves preparing the surface properly and then re-applying the paint using the correct technique.

Here are the steps to fix a cracked spray paint finish:

Step 1: Let It Dry Completely

Before you do anything, you need to ensure the paint is fully cured. Depending on the type of paint, this can take anywhere from 24 to 48 hours. Allowing the paint to dry completely lets any remaining solvents escape, which is crucial for preventing further cracking when you sand.

Step 2: Sand the Surface

This is the most important step for a successful repair.

• For minor cracking: Use fine-grit sandpaper, such as 220-grit or higher, to lightly sand the entire cracked area. Your goal is to smooth out the cracked surface and create a uniform, smooth base for the new coat.
• For severe cracking or “alligatoring”: You may need to start with a coarser grit sandpaper, like 120-180 grit, to remove the cracked paint layers. Then, switch to a finer grit to smooth the surface completely.

Step 3: Clean the Area

After sanding, the surface will be covered in dust and debris.

• Use a clean, dry cloth or a tack cloth to wipe away all the sanding dust.
• For a flawless finish, you can also use a mild degreaser or rubbing alcohol on a lint-free cloth to ensure the surface is completely free of any oils or residues. The surface must be perfectly clean and dry before you re-apply any paint.

Step 4: Re-Prime (If Necessary)

If you had to sand down to the bare surface (the original material, like wood or metal), you should apply a new coat of primer. This step ensures proper adhesion for the new layers of spray paint. Use a primer that is compatible with your spray paint.

Step 5: Repaint with Thin Coats

This time, use the proper technique to prevent cracking from happening again.

• Apply multiple thin coats: Instead of one heavy coat, apply several light, even layers.
• Follow manufacturer recoat times: Read the instructions on the can for the recommended drying time between coats. Waiting longer is always better than rushing.
• Proper distance and motion: Hold the can about 8-12 inches from the surface and use a smooth, steady, back-and-forth motion, slightly overlapping each pass to avoid lines.

Pro-Tips to Avoid Spray Paint Crack

• Work in the right conditions: Paint in a well-ventilated area with a temperature between 50°F and 90°F (10°C to 32°C) and low humidity. Avoid direct sunlight.
• Shake the can thoroughly: Make sure the paint and pigments are well-mixed by shaking the can for at least two minutes before you start.
• Use compatible products: If you’re using a primer or clear coat, ensure it is chemically compatible with your spray paint, preferably by using products from the same brand.

To avoid cracking, prioritize patience and proper technique. Always apply multiple light coats instead of one heavy one, ensure the surface is clean and prepared, and work within the manufacturer’s recommended temperature and humidity ranges. By following these best practices, you can achieve a smooth, durable, and professional-looking spray paint finish.