If you’ve been following glass industry trends for a while, you’re probably familiar with first-surface acid-etched glass. You’ll see it pop up in case studies, bird friendly articles, and posts about daylighting. What makes this treatment so popular? There’s its versatility, of course, and the fact that it works well with other treatments like energy efficient coatings. Then again, the durability of this finish could also be the deciding factor, or the way it can optimize light and help contribute to accreditation under green building systems like LEED®. As the bird friendly building movement picks up speed, many architects are choosing first-surface etch for its effectiveness at preventing collisions. In short, there’s a lot to love about a first-surface acid-etch finish.
What exactly is first-surface acid-etch?
Architectural glass surfaces are numbered according to their position in final installation. The outermost surface is known as ‘first-surface’, or ‘surface one’, while the inward facing side of the same pane is called ‘second-surface’, or surface two. In a double- or triple-glazed unit, the numbering continues through third, fourth, and potentially fifth and sixth surfaces. For the purposes of this article, we’ll be talking mostly about the first-surface.
Acid-etch, for its part, involves exposing all or part of a glass’ surface to an aqueous acid solution, resulting in a smooth yet semi-opaque surface finish. At Walker we use highly specialized acid solutions to achieve a variety of finishes, from full strength Opaque to semi-transparent Satinlite.
Why choose a first-surface treatment?
Since glass is transparent, why does it matter which surface is etched? It’ll be the same regardless, right?
Let’s look at five key areas where first-surface treatments can outperform other techniques:
Before we get into the nuts and bolts of performance and aesthetics, here’s one very simple reason to choose first-surface etched glass: LEED® certification.
Used wisely, the right glass can be a major advantage when pursuing LEED® ratings. Walker Glass first-surface etched glass is particularly helpful under the following four categories:
- Energy and Atmosphere (when combined with a Solarban® low-e coating on surface two)
- Materials and Resources
- Indoor Environmental Quality
If you’re involved in LEED® building projects, you’ll want to keep our checklist of LEED® v4.1 credits available with Walker Glass Products close at hand.
Maintenance and Durability
Acid-etched glass is durable by its very nature. Glass is a stable and non-reactive material, and the acid-etching process only makes it tougher. Unlike ceramic or frit enamels and silicone coatings, an acid-etched finish doesn’t add any additional material that may discolour or wear off over time. Instead, it changes the texture of the glass surface. This makes it easy to clean and impervious to UV exposure, wind, dirt, and weathering in general. Maintenance staff at the National Aviary and the University of Saskatchewan report that their institutions’ acid-etched glazing shows no sign of wear or weathering since installation in 2018, and that it is as easy to care for as untreated glass. In fact, testing shows that full surface acid-etched glass outperforms regular float glass in its strength and resistance to wear.
For more information about the strength and resistance properties of full surface acid-etched glass, please refer to Tables A2 and A3 of our Product Specifications.
Full surface etch can do a lot to help optimize daylighting. It diffuses sunlight without reducing VLT, softens glare, and reduces exterior reflections. This is especially useful for skylights and upper panels, which are crucial for effective daylighting and need not be transparent. CJMW Architects used acid-etched glass to great effect when they designed the Johnson Volvo showroom in Durham, NC. The Velour finishes on the showroom’s oversize glass panel bathe the interior in pure, even daylight to bring out the best in the cars on display.
For more information on visible light transmittance and diffusion through full-surface acid-etched glass, please refer to Tables B1 and B2 of our Product Specifications.
First-surface etching can add a wide variety of matte and semi-gloss effects to glass, making it a popular choice for façades and statement panels. One outstanding example is McMaster University’s Peter George Centre for Living and Learning. Diamond Schmitt Architects used a trio of custom acid-etched Nuance patterns to transform the residence’s façade into a rich collage of tones and surface qualities. Each pattern in the building’s glazing presents different levels of reflection and transparency, and all three give students and faculty a clear view of the campus while reducing glare.
We explore this project’s design elements in our article, Daylighting with Custom Acid-Etched Glass.
Another way that designers use first-surface etch is as a blank canvas for their most creative ideas, something we highlight in our article, Full Surface Acid-Etched Starphire® Glass: The Designer’s Choice. Etched glass presents a matte surface that doesn’t reflect surrounding colours the way standard float glass does, so back-painting and coloured laminates can really stand out.
NBBJ Architects used Starphire® low-iron glass with a first-surface Velour etch to great effect in the glass fins at the base of Amazon’s Day 1 tower in Seattle, WA. The ultra-clear glass and matte finish provided a perfect stage to show off subtle colour variations in the specialty laminate applied to the back of each fin.
Experts agree that first-surface patterning is most effective at deterring bird strikes because it’s the only surface which is visible in most lighting conditions. During daylight hours, conditions are usually much brighter on the outside of a building than on the inside. This creates a mirror effect on the glass, whereby it reflects images off the first surface. It’s the same phenomenon we all experience when we see our own reflection looking out a window from a brightly lit room toward a dark nighttime sky, but in reverse. As a result of this phenomenon birds often mistake the images of trees, sky and other environmental elements on windows for the real things, and fly straight into their reflections.
The problem is exacerbated by environmental elements like mature trees, gardens and green roofs. Ironically, these welcoming habitats for birds can become deadly when they reflect off our workplaces, schools, and homes.
Reflection can also be a problem with railings and spandrel glass, even though they don’t generate the same light/dark effect as windows. First-surface markers solve the problem by interrupting image reflections. Their matte finish prevents any reflections off the markers themselves. As a result, a bird flying toward a pane of glass with first-surface patterning will see the pattern and avoid flying into it, even on a bright, sunny day.
At Swarthmore College’s Whittier Hall, markings on the first surface of the glass are clearly visible through reflections from the surrounding environment.
Governmental bodies across North America recognize the superior effectiveness of first-surface treatments, and legislate accordingly. The city of Toronto, Ontario, set the standard for bird friendly glazing with their Bird-Friendly Development Guidelines, which call for first-surface markers in preference to inner-surface treatment. This preference becomes law in the latest version of the city’s Green Standard. Beginning on January 1st, 2022, visual markers must be applied to the first surface of the glass for it to qualify as bird friendly glazing.
Many cities and organizations have followed Toronto’s lead, and implemented their own requirements for bird safe glazing with first-surface markers. Examples include the Canadian Standard Association’s Bird-friendly building design guide (CSA A460-19). Palo Alto, CA, Richmond, CA, Portland, OR, and Ottawa, ON also include first-surface markers in their guidelines for bird friendly building. To be compliant, buildings in these regions must use glass with first-surface patterning as indicated in the codes. The National Glass Association recommends first-surface markers in its updated guide, Best Practices for Bird-Friendly Glazing Design.
AviProtek® bird friendly glass and full surface Walker Textures® acid-etched glass are both excellent bird deterrent glazing options. Full surface etch is well suited to skylights, spandrel and non-vision panels. Its full coverage makes it highly visible to birds.
On the other hand, AviProtek® bird friendly glass combines bird deterrence with transparency. Most AviProtek® designs meet the 2×4 rule, which is widely accepted as the standard for bird deterrent patterns. Some also meet the 2×2 rule, which protects smaller species like hummingbirds. Yet these patterns cover as little as 1% of the glass surface, making them an efficient and unobstructive choice for bird friendly glazing. Staff, students and visitors at institutions like the National Aviary, the University of Saskatchewan, and the Oregon Zoo Education Center agree that the bird friendly markers do not interfere with their views of the surrounding environments.
AviProtek® products have been tunnel tested by the American Bird Conservancy, making them a viable candidate for LEED® Pilot credit SSpc55, Bird Collision Deterrence. Architects in New York City can also use them as bird deterrent solutions under Local Law 15, which is based on ABC’s Threat Factor rating system.
Please see Table A2 of our Bird Friendly Acid-etched Glass Booklet for a list of AviProtek® Threat Factor ratings, pattern density, and more.
We on the Walker team have seen our share of bird friendly projects since launching AviProtek® bird friendly glass. Based on our experience, we can say this without a doubt: first-surface bird deterrent patterns work. They work very, very well.
Some recent projects using first-surface etched glass deserve special attention, for the proven effectiveness of their bird friendly glazing. At the National Aviary, staff have monitored the Tropical Rainforest and The Garden Room for bird strikes since they were finished in 2018 and 2020, respectively. Both buildings feature glass walls with first-surface etching. AviProtek® pattern 213 in the Garden Room gives guests a clear view of the surrounding park, while a full surface Velour etch softens daylight in the Tropical Rainforest. At first, the Aviary’s staff were concerned that the large expanses of glass presented by these two structures would endanger the local birds. However, after careful daily monitoring on both sites, they haven’t seen a single sign of collision.
For the full story of these buildings, read Bird Friendly Glass at The Garden Room of the National Aviary and Bird Safe Glass at the National Aviary
Of course, there’s more to first-surface etching than the first surface. It’s not only about which surface you treat. It’s also about which surface you don’t.
Surface two plays an important role in high performance glazing. For example, a low-emissivity product like Solarban® from Vitro Architectural Glass can be a powerful component of an energy efficient building envelope. However, its effectiveness depends on placement. For optimal performance, solar control coatings should be applied to surface two. A first-surface acid-etch leaves the second surface free for low-e coatings, so you can reap the full benefits of both treatments.
The Pikes Peak Summit Visitors Center in Colorado uses AviProtek® E bird deterrent glass with acid-etched pattern 213 on surface one and a Solarban® 70 low-e coating on surface two.
As we’ve seen, first-surface acid-etched glass is a versatile solution to a wide variety of glazing challenges. These include sustainable building considerations like LEED® accreditation, energy efficiency, and bird deterrence. You may also have visual factors like light flow and aesthetic effect in mind, or be concerned about a glazing system’s durability and ease of maintenance. Whatever your priorities, first-surface etch might be the perfect fit for your next project.