Refinishing is destructive by nature. Polishing, buffing and grinding all remove material from watch cases and bracelets, by various degrees. As watchmakers, we try to keep the reduction of material to a bare minimum, but some material is invariably lost to the process. This is why plated watches cannot be refinished (their coatings are too thin), and why watches can be destroyed through “overpolishing.”
There is, however, a rare, advanced and dangerous technique that allows a watchmaker to add material to a case, allowing otherwise impossible repairs to be completed.
Damage to corners and case edges/borders are the trickiest dents to remove. A dent in the side of a case is easily eliminated by buffing away the material around the damaged area, lowering the entire plane to the level of the impact. Most scratches and dents are extremely shallow—they seem much deeper than they really are—so most damage can be removed this way.
Dents on the border between two surfaces, however, require material to be removed from both surfaces. This dramatically increases the destructive nature of the polishing action, and can quickly distort the visible geometry of a case, which is the number one thing we try to avoid during refinishing. Typically, bad dents on corners and lug borders are reduced, but not removed. Laser welding changes all of that.
Laser welding is a marvelously powerful tool that allows us to actually put metal back onto a case. For bad damage (especially on border areas) we can now fill dents in, rather than remove material around them.
Welding differs from brazing and soldering in that everything melts together, both the base metal and the weld metal. This requires high heat, and for repairs like this, it also requires high precision. Lasers are just the thing. Using finely-focused laser pulses, we’re able to melt thin welding wires onto a watch, filling in dents without damaging other areas of the case.
The technique is complicated and delicate, but the trick is to build up material without leaving too many voids between the welds. Any voids will show up as pits or cracks in the polished watch, and need to be filled in later.
Through extremely careful cutting (filing or grinding, depending on the situation), the “extra” weld material is removed until the original case lines are restored. At that point, it’s polishing as usual.
Done correctly, laser welding can make a bad dent disappear. Done poorly, and you can destroy a case completely. This is a technique best used extremely sparingly, and only for repairs like this that traditional refinishing would fail to correct. Some extremely skilled people are able to dramatically rebuild overpolished watches with serious amounts of welding, but that kind of work has its own Ship of Theseus-esque ethical considerations and falls outside the purview of retail watchmaking.
Watchmaking student at the Lititz Watch Technicum, formerly a radio and TV newswriter in Chicago.