Best Practices, Operations, V8I5

Maximize Your Paint Process

(Photo courtesy of PPG)

A shed coated with honey gold stain has always been a classic look across the shed industry. 

However, a growing number of sheds are being built with substrates that have a pre-primed surface, eliminating the ability to get the rustic stain finish that many shed builders and customers prefer. 

True exterior penetrating stains are designed to penetrate and seal raw wood. They were never intended to go over a primer or lay on a surface. Though some builders use them over pre-primed substrates, it’s not recommended and can result in long-term durability issues. 

A better solution for many shed builders is a waterborne semi-transparent urethane coating. 

Developed to provide painters with the ability to achieve a rustic stain-like appearance over a pre-primed substrate, this type of coating provides superior exterior durability when compared to acrylic paints or exterior penetrating stains.

For this reason, waterborne urethanes have quickly become the premium variety of coating for the shed industry. There is, however, a potential downside when it comes to application. 

While some painters have mastered the application of waterborne urethanes, others have struggled. In fact, there are painters who have resisted using them altogether because they haven’t grasped the proper application technique.

When applying a semi-transparent coating over a primed surface, the goal is to make it “look” stained. This means no streaks, dark spots, sags, or runs. To accomplish such a look, it’s important for painters to adjust their application method from the way a solid color is applied.

The following best practices will help painters achieve a stained-like appearance when spraying waterborne semi-transparent urethane coatings:

• Change the tip size. For solid color paints, most painters use a 415 or 517 tip. These tips provide a wide fan and a good volume of material. While this is important when trying to cover/hide the surface, it’s not necessary when applying a semi-transparent urethane. Instead, a 513 tip is recommended. This will give painters a 10-inch fan and just the right volume of material. The wider fan will help painters overlap their spray pattern and achieve an even finish.

• Spray with the grain. If the grain of a board runs vertically, then spray up and down. If the grain runs horizontally (like when lap siding is used), then spray left and right. DO NOT SPRAY both vertically and horizontally on the same surface! If a coating is sprayed in multiple directions, dark stripes and an uneven finish will usually be the result. 

• Overlap the spray pattern. Whether spraying up/down or left/right, it’s important that each pass overlaps the previous pass by 50 percent. This technique will help eliminate light spots and streaks.

• Spray into or toward the corners/edges of trim boards. Keep the pattern of vertical or horizontal spraying (not both). Only spray in or toward the trim pieces—not all the way across. Otherwise, a light area or “halo” above the trim board could develop and become difficult to hide. Spraying up to the bottom side/edge of the trim and then spraying down to the top side/edge of the trim can eliminate this halo effect. 

• Practice, practice, practice. Painters who are new to spraying waterborne semi-transparent urethane coatings may want to practice first on scrap boards to get the technique down before spraying a full shed After all, practice makes perfect!

We hope you find this article helpful. If you have any questions or would like additional information on spraying waterborne semi-transparent urethane coatings, please reach out to your local PPG representative.       


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