In the Details: Turning Blue
As early as the 16th century, watchmakers used heat bluing to prevent the steel components of their watches— hands, screws, and sometimes even the dials— from succumbing to oxidation and rust.
Prior to the advent of stainless steel, the heat bluing technique served two functional purposes: protecting the steel components of the watch and strengthening these tiny components to prevent them from becoming brittle, which is especially important for screws. When placed under intense heat, the steel forms a protective oxide coating, and when the temperature is dialed in just right, this coating takes on a deep blue hue.
And while advancements in technology and metallurgy have rendered the functional necessity of the technique largely superfluous, it’s easy to see why modern watchmakers carry on the traditional method.
Traditionally, the technique occurs over an open flame, with the miniscule components placed upon a small bed of brass shavings atop a copper tray to allow for even heat distribution. The components must be cleaned and prepared, free of any sort of oil that would show up as an imperfection during the bluing process. The watchmaker must consider if the material is the same thickness across, or if there are thinner areas that will blue quicker than others, and there needs to be consideration given to sets of hands to ensure they achieve the same exact same shade.
The color-changing process occurs across a range of temperatures with intermediate colors of yellow, gold, and purple, occurring before blue is reached at around 280-300℃. Colors earlier in the spectrum provide greater hardness but also become more brittle, while the heat required to achieve blue results in the proper balance of strength and oxidation as well as a pleasant look aesthetically. Skilled watchmakers don’t necessarily keep an eye on the temperature gauge, but rather rely on their experience to watch as the color changes to their desired hue. It is up to the skilled hand and eye of the watchmaker to create matching components
While this approach has been replicated with everything from chemical treatments to electric heaters, detail-minded watchmakers and watch enthusiasts know that heat-blued watch parts signify an extra level of craftsmanship and attention to detail. As an homage to the great masters of watchmaking, the presence of heat-blued components can tell you as much about a brand’s passion for detail
Beyond adding layers of depth, contrast and color to any watch, the presence of heat-blued components pays homage to the great masters of watchmaking, clueing discerning collectors into the level of care put into their favorite timepieces.
From A. Lange & Söhne’s meticulous movement finishing to De Bethune’s vibrant experimentation with blued titanium, scroll on to see some of our favorite watches made with heat-blued materials.
