Sofia Martinez
Spray paint bubbling is a common issue that can occur due to various reasons. In this discussion, we will explore the reasons behind spray paint bubbling on plastic surfaces and provide solutions to achieve a smooth and attractive finish. From improper surface preparation and rushed application to environmental factors like humidity, understanding the causes will help prevent and address this frustrating problem.
Why is my spray paint bubbling on plastic?
| Characteristics | Values |
|---|---|
| Resins in the plastic | Need to be baked out and then sealed with a plastic prep |
| Type of plastic | Some plastics have resins that will not accept paint |
| Surface contaminants | Wax or oil deposits on the surface |
| Surface preparation | Improper cleaning of the surface before application |
| Rushing the job | Not enough dry time between coats |
| Temperature | Too cold or too hot outside |
| Paint type | Some paints need up to 72 hours to cure |
| Paint brand | It is possible to use mismatched products if recoat times are followed |
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What You'll Learn
Resins in the plastic
Resins are organic compounds, which can be natural or synthetic. They are usually in a viscous liquid state or an amorphous solid state, depending on the temperature. Synthetic resins are used as ingredients in plastics, and the process of creating plastics from resins involves applying heat and pressure to mould or shape them.
The "raw" plastic, or resin, arrives at the injection moulding company as small pellets. It is then processed, dried, heated, and injected into moulds. This process is important, especially for thermoset plastics, which fuse when heated and cooled.
When it comes to spray painting, resins in plastics can cause bubbling. This is because certain resins in plastics do not accept paint and need to be baked out and then sealed with a plastic prep.
To avoid bubbling when spray painting, it is important to ensure the surface is clean, dry, and free of any substances like grease or oil, which can be a result of the manufacturing process. Additionally, the paint should not be applied too soon after shaking the can, and the can should not be held too far away from the surface being painted.
If bubbling does occur, it can be fixed by sanding the surface with fine-grit sandpaper, wiping it with a dry cloth, and then repainting. Alternatively, the paint can be stripped, but this is a more time-consuming and labour-intensive process.
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Surface contaminants
To prevent bubbling due to surface contaminants, it is important to properly clean and prepare the surface before painting. This includes removing any dirt, grease, or other residues that may be present. Lightly sanding the surface can help create a smooth base for the paint to adhere to. It is also recommended to use a primer before applying the spray paint, as this can help improve adhesion and reduce the likelihood of bubbling.
If you are working in a humid environment, it is important to allow for a longer dry time between coats. Even if you are spraying in a garage or enclosed space, the humidity can affect the drying time. Similarly, temperature can play a role in drying time. For example, metal surfaces tend to stay colder for longer, so it is important to ensure that the temperature is between 50 and 90 degrees Fahrenheit when painting metal.
In some cases, it may be necessary to strip the paint and start over if the bubbling is extensive. However, for minor bubbling, you can try piercing the bubbles with a fine sewing needle, flattening them with a paint scraper, and then applying a new coat of paint.
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Poor weather conditions
High humidity can prevent paint from drying properly, leading to bubbling. This is true even if you are painting indoors, as the humidity in your garage or workspace can be similar to that outside. To avoid this, paint in low humidity conditions, ideally below 50% relative humidity. You can use a dehumidifier or fan to keep humidity in check while the paint dries.
If it is too cold outside, the paint may not dry properly and could bubble. This is especially true for metal surfaces, which stay colder for longer than other materials. Make sure the temperature is within the recommended range for spray painting (between 50°F and 90°F).
While less common, high temperatures and hot, humid weather can also cause bubbling. This is because high temperatures can cause the paint to dry too quickly, leading to an uneven finish.
In addition to the weather, the condition of the surface being painted is also important. The surface must be clean and dry before painting. Contaminants such as dirt, dust, grease, or oil can prevent the paint from adhering correctly, leading to bubbling.
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Incorrect application technique
Spray paint can bubble for a variety of reasons relating to incorrect application technique. Bubbling can occur when the paint is applied too thickly in one go. It is better to apply a lighter initial spray and then a thicker coat five minutes later or within an hour, depending on the paint. If you wait too long to apply the second coat, this can also cause bubbling. It is important to follow the recoat times on the label of the paint and primer used. Some paints need up to 72 hours to completely cure.
Bubbling can also occur if the paint is applied too soon after cleaning. The object needs to be clean and very dry before painting. It is important to ensure that all contaminants, such as wax or oil, are removed from the surface before painting.
The distance from which the paint is sprayed can also cause bubbling. Holding the can too far away from the surface can cause issues. It is recommended to hold the spray paint bottle about 6 inches away from the surface and to move your hand at a steady rate to apply the paint.
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Incompatible paint products
Spray paint bubbling can be caused by incompatible paint products. Paint products from different brands may not work well together, leading to bubbling and other issues. This is especially true if the recoat times are not followed precisely. Many paint products have specific instructions for how long to wait between coats, and deviating from these instructions can result in bubbling. For example, Rustoleum's Painters Touch 2X primer for plastic recommends waiting 5 days before recoating with the final finish.
In some cases, it may be necessary to wait longer than the recommended recoat time, especially in humid environments. Humidity can slow down the curing process, and if the paint is not fully cured, applying a second coat can cause bubbling. It is also important to ensure that the surface is clean and dry before applying paint, as contaminants such as wax or oil can interfere with the adhesion of the paint and cause bubbling.
If you are using multiple paint products, it is important to check that they are compatible. For example, one source mentions that Rustoleum primer and Krylon play well together, but other combinations may not work as well. Additionally, it is generally recommended to avoid mixing rattlecan paint brands, as this can lead to bubbling and other issues.
To avoid issues with incompatible paint products, it is important to read and follow the instructions on the paint products you are using. This includes allowing sufficient drying and curing time between coats, as well as properly cleaning and preparing the surface before painting.
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