Why and When to Use Stain

Throughout my career I have elected to not use stain, preferring the natural patina of plain concrete. This works especially well if the concrete pours are good and there is ample relief, creating shadow play over form. A good example of this is the MSE wall patterning for the Aurora Interurban Bridges. These are precast concrete panels created for MSE walls.

A natural patina is very reactive with light, changing its hue throughout the day. This wall shows the glow of late afternoon sunlight.

Another good example of plain concrete allowed to age and patina naturally is the La Cholla Project, in Tucson, AZ. This project features nearly 50,000 sq. ft. of poured-in-place concrete.  This project, created in 2001, is over 10 years old. Its surface is enhanced by the play of elements and the local soil over its surfaces. It appears stained, but it is not. It is coated in a thin veil of dust that casts the same hue as the local earth. This is one of my favorite projects.

Below is a detail of the surface.  Even though this work is poured-in-place the detail and consistency of the pour is constant throughout the project.  However, this is not always the result of field work or even precast work.

This past year, I had two projects that had surface issues. The first one, created for 375 E&W, the Outer Loop Highway in El Paso, TX, was an MSE wall system with over 400,000 sq.ft. of precast wall units. While precast is normally a more reliable method of producing uniform panels, in this case that did not happen. The colors of each batch pour varied widely from others, creating a patchwork quilt look that over powered the design.  Also, during the mold process, Precision Board was unwittingly substituted for Sign Foam “the brand,” and this created a chemical reaction with the urethane. The result was an inconsistent surface with a variety of blemishes that appeared during the casting process.

For this application, I decided to stain the concrete. Stain offers forgiveness for all that is not perfect. Stain provides a more uniform surface and works well to cover blemishes and discoloration. Below is an example panel, close-up, that has been stained with an earth-toned hue. This summer, the entire project will be stained to match this hue.

After testing 3 or 4 colors on 8 different units, we selected Sherwin Williams Sandy Ridge, a warm, neutral earth tone. This color complements the warm hues of the El Paso soil, adding contrast.

Recently, I applied stain on another project created for Arlington Boulevard in Arlington, VA. We experimented with two methods. On the left, we applied a pigmented sealer. On the right, we applied a “wet look” clear sealer.  The pigmented sealer refined the look of the surface, allowing the relief to dominate. The “wet look” clear sealer exaggerated the surface variation and dominated the relief. We decided to move forward with a pigmented sealer.

During the installation of the MSE walls, we test 3 more pigmented sealers. We decided to use Sherwin Williams Sandy Ridge for this application too. Climate affects how color reads. Under the cloud cover of Virginia skies, this color looks entirely different from the application in El Paso. Still, it is complementary to the Arlington soil.

Our intention is to apply a stain that enhances the relief and reflects the hues of the local landscape. While the image below is not stained, our intention is to match this hue with a similar earth tone stain that complements the site and allows the relief to be visually maximized throughout the project.

Below is an example of a project along I-405 in Kirkland, WA, that is completed and stained. The color selection is based on the site and setting. As Kirkland resides in a northern climate, the stain selection is a neutral taupe to complement the site and landscape. This project has been in place over seven years.

This image shows a detail of the wall patterning with a taupe stain. This project seems to be wearing and weathering well.