A Mosaical Divertimento

Divertimento (from the Italian divertire — to amuse) is a musical genre. The mood of the divertimento is most often lighthearted, and it is generally composed for a small ensemble.
–Wikipedia

This is the tale of a small ensemble of Seattle mosaic artists of varying ranges of experience – Kelley Knickerbocker, me (Debbie McLaughlin), and Todd Campbell – who collaborated in summer 2012 on a public mosaic mural. A 50 square foot wall with 10,000 tesserae, this mural, entitled Divertimento, covers the southern retaining wall of the Hazel Miller Plaza in Edmonds, Washington. During this, our first collaborative large-scale mosaic, we experienced all the thrills and panic that more experienced public mosaic artists undoubtedly remember from their first project.

This article offers more than just our post-mosaic bliss, however. Our collaboration yielded some new techniques, and we want to share the process, pitfalls, and resolutions. Furthermore, amazing results can happen when master mosaicists and ‘minions’ work together and forge a blend of the tried-and-true and the experimental.

First we came up with a design to meet the city’s requirements for “background music” on the wall that would compliment – and not compete with – the dazzling steel and glass railing above it. After two iterations the design was approved, and we settled into pre-processing the aforementioned 10,000 pieces. Bins piled up over the first couple of weeks: glazed & unglazed tile, Bedrock recycled glass, beads, stained glass, pottery shards, and smalti. Not content to settle for only our rectangular pieces, we also decided to accentuate the concentric circles that are the key design element (referencing the glass roundels in the railing above) with hundreds of circular tesserae and ringsawn spiral cuts.

We constructed this mosaic on mesh with thinset in the studio in two major sections – essentially the two halves of the wall. We created large “sheets” of substrate: one layer of mesh coated with Laticrete 254 thinset, because we wanted firm, sturdy, easily liftable sections. Rather than cut smaller sections to work on individually, we decided to leave the entire half-wall substrate – cut to fit the weird, triangular-trapezoidal shape of the wall – intact and then section it later.

We then began to lay the tesserae, and build/affix the 3D sections that would stand from ½” – 2” out from the wall. Keeping the half-wall substrate intact meant we could much more easily control the andamento and ensure the overall harmony across the wall. We knew we could cut the sections with a utility knife once the tesserae were laid and firm. By the way, baggies for thinset application are an essential budget line item for tidy, non-stop production!

And here is where the magic began to happen. Todd– the team member newest to the world of mosaic –asked a lot of great questions throughout this process, and we came to realize just how powerful those “innocent” questions can be. While mulling over the best sectioning method and discussing the complications of on-site grouting of an extremely dimensional work – for the umpteenth time– Todd asked the game-changing question: “Just out of curiosity, why wouldn’t we pre-grout the sections?”

Kelley and I laughed later that we both thought, but didn’t say: “Pre-grouting just isn’t done!” But for Todd’s benefit we talked through the possibility and started to brainstorm the pros and cons of this idea. In the end, it’s exactly what we opted for: cutting the substrate sheets into sections, pre-grouting (with SpectraLock epoxy grout)and grinding the sections in the studio, and then installing. Installation was slated for a very hot week in August , and we didn’t relish the idea of grouting a wall lower than waist-height in 80 degree heat. Pre-grouting saved our backs, made for a cleaner job, allowed us to have larger, more rigid sections, and and cut on-site installation time from five days to two.

The day before installation we laid all the sections out to double check their fit and anticipate any possible problems. To our surprise and shock, two of the grouted sections were slightly warped, not absolutely flat. This was the most gut-wrenching moment of the process, producing some tense moments as we debated solutions. Should we try to crack the section and then re-grout the crack? If so, how would we crack it – try to determine & direct the crack, or simply press on the section and let it crack where it needed to? What else could we possibly do?

Two happy “accidents” occurred next: First, Kelley ended up cracking one piece while turning it over and gently pressing it against her leg. We marked the cracks in the now-flat section for later re-grouting. The other section proved more worrisome: it was a full circle, about 2 feet in diameter, with another square foot below the circle. In addition, the circle had a raised section: a piece of Wedi with tesserae: super solid – yet scarily warped. We think this happened because some of our section transfer boards were not rigid enough and bent as the grout was curing. You can’t defy gravity!

While transferring sections back to the studio, Debbie set this section up against the exterior wall, and 30 minutes later noticed that it seemed flatter. Our hearts leapt as we realized we might be able to flatten the piece while the grout wasn’t fully cured. We laid the section out flat in the hot sun, then bricked it down, and the next morning the section was as flat as could be. Yet one more reason to love Laticrete products!

Installation had its hiccups, but overall, we installed 50 square feet of mosaic in two days, including final grouting of seams and caulking of edges. We even managed a decent lunch hour both days and clocked out before 5 p.m.!

Todd’s willingness to question, think aloud, wonder, and see new possibilities resulted in a technique that I know we’ll use again in the future. We had countless other moments of learning, things we would do differently and better. But one thing I would absolutely do again is work with Kelley, a master mosaicist, and Todd, a fast-learner and fearless questioner. Each of us made substantial contributions to this project. The weaving of our conceptual contributions and actual labor make Divertimento a timeless work of art for the city of Edmonds and a pivotal experience in our development as mosaic artists.