In my last article, I told you about the Steeldive SD1975S bronze tuna I purchased. Now, I will tell you what I did with that watch; a journey into the world of amateur chemistry with a little bit of artistic flair thrown into the mix. My vision was the Bronze Tuna Shipwreck Patina Project; not the gradual tarnishing that naturally occurs on such watches, but my own somewhat fanciful idea of what extreme aging and wear might look like. It was an absolute blast, and I am proud of the result. I’ve already shown my steps on Instagram, but this post will get into the details, including some mistakes that you would be wise to avoid.
First, I needed a donor watch. I already own several bronze/brass watches, but I like them just the way they are. I’ve only ever attempted the mildest of patina experiments (boiled egg in a bag) on one or two, and that’s the way they are going to stay. We’ve covered forced patinas on these pages before (see Mr. Alistor’s excellent “Patina Science“). Chemically forcing a patina will radically change the appearance of your watch, and while there are several methods of removing it, I have found that some stains are stubborn, requiring heroic polishing efforts to remove completely, if at all. Moreover, exposure to chlorides, like plain old salt, can create an irreversible reaction known as “bronze disease” that breaks down the metal itself. If I was to launch a full-bore assault on a bronze case, it couldn’t be on a watch with which I had already formed an attachment. It had to be a new one purchased for this specific purpose.
I settled on a tuna close right away. I got the bug after trying on a fellow collector’s original 1970s vintage Seiko “Grandfather Tuna” at an event. I had nothing like that in my collection, and given the deeply weird nature of the shrouded design, I thought it would look even cooler with a creepy patina. Seiko does not dabble in bronze, so I looked at the many Chinese factory brands that turn out homage watches. The Steeldive was the clear winner for four reasons: 1) it was faithful to the original design, 2) it was inexpensive (under $200); 3) according to the catalog listing, it had a stainless steel case under the exposed bronze, so I could be reasonably sure any violence I inflicted upon it would not damage the important parts; and, 4) the lugs were gold, not silver like some of its rivals. It was a good-looking watch too. That gold-on-black dial muted the logo and text and keyed well with the case. I clicked “add to cart,” and in no time, the watch was on my doorstep.
Taking stock, I discovered a nearly pristine shroud and bezel, an already darkened crown, and a shiny gold underside and lugs that I assumed were PVD-coated. I briefly considered removing the shroud to inspect it further and prevent the screws from freezing in place as the oxidation built up, but having read more than one story in the forums about owners of non-Seiko tunas struggling with stripped or broken screws, I decided to leave well enough alone. That shroud was never coming off anyway. I removed the strap and buckle.
In a few days, I discovered that a light patina had already started to form where I had handled it. Oxidation works fast, and oil prevents it, so it is not uncommon to see a patinated fingerprint (or, more accurately, a negative of a fingerprint) develop on a bronze watch. I did not want that, so I rubbed the shroud clean with a Cape Cod cloth, then wiped the whole watch with an alcohol swab, handled it with gloves after that, and wiped it clean any time I touched it bare-handed. It was ready to go.
My plan was to use salt and vinegar fuming followed by liver of sulfur. I could have browned it up a bit first by sealing it in a ziplock bag with a crushed hard-boiled egg, but I figured the vinegar would darken it pretty quickly, and I wanted the salt to attack the surface without any barrier in between.
I set up my first fume chamber in a small plastic container with a sealing lid. Before I placed the watch and buckle inside, I washed them with a bit of soap and water, then doused them in a brine of 1 tablespoon of sea salt dissolved in about a cup and a half of water. I added some paper towels soaked with heated white vinegar on top of which I placed two plastic bottle caps to elevate the items. I didn’t want them sitting in the vinegar; I needed the fumes to do the work. For this round, they would be face up; for the next, face down. Once placed, I gave both pieces a spritz of water and heavily seasoned them with coarse sea salt. No turning back now. The bronze tuna shipwreck patina project was underway.
Heat accelerates the patina process, but you don’t want so much heat that you damage your watch. I warmed up the vinegar in a microwave to hot, but not boiling, about where you might want a cup of tea. Pouring it on the paper took some of the heat out of it, and I’m sure it lost even more through the plastic walls of the container. I placed the whole thing out in the sun on my asphalt driveway on a hot Virginia summer day. Condensation formed right away, which was fine by me. I figured the droplets would prove interesting.
The salt and vinegar went to work, forming blue blooms in no time. Seven hours later, there was blue-green and brown crust everywhere. It already looked like something from a coral reef, but I knew most of that would rub right off. I noticed that there was weird orange goop on the watch too, almost like rust but more like the Gatorade cap it had been resting on. Uh oh.
Something in that chemical sauna had leeched the orange dye out of the cap and onto the watch. The buckle, sitting on a white cap, was unaffected. Lucky for me, the goop washed right off. Lesson learned: everything that goes into the fume chamber must be evaluated for its ability to react, even things we might think are inert. I would be reminded of this again shortly.
I let the items dry overnight before cleaning them in cool water with a soft toothbrush and then rubbing them down with a clean cotton rag. Now I could appreciate the effect.
Phase 1 had turned out exactly as I had hoped. The surface was darkened, and there were great rings where the salt crystals had settled.
I was surprised to see a patina sticking to the underside and lugs. Steeldive listed this watch as having a stainless case, and those lugs looked for all the world like polished gold PVD plating, which, like the stainless caseback, should not form a patina, and yet, here it was. In the interest of science, I went at a spot inside the lugs with a sharp tool. Scrape as I might, I never saw steel. I have since confirmed with Steeldive that the entire case is indeed bronze. Only the caseback is stainless.
Worried that I might inadvertently fuse bronze parts together, I took care to rotate the bezel and unscrew the crown (after the exterior was thoroughly cleaned and dried) so I could clean the underside of the crown and its threads. This required some patience, the application of white vinegar with a fine-tipped paintbrush, careful poking with a wooden toothpick, and a wipe with a cloth. Vinegar? The same stuff that caused the patina? Yes. Direct application of vinegar will dissolve the patina, but you don’t want to leave it on there. You also want to do this while holding the watch crown down, so you don’t knock any debris into the case. The threads were pretty clean, so I suppose I could have left this part for last, but a surprising amount of moisture had made its way underneath the crown, and enough patina formed between the crown and the case to scrape. Better safe than sorry.
For round two, I ginned up a new chamber made from a tall plastic container. I decided to forgo the paper towels and just pour hot vinegar into the bottom. The watch was suspended face-down from paper clips through the drilled lug holes, and the buckle was hung alongside it. Again, I wet both pieces, but this time I encrusted them in finely ground sea salt. It was raining, so I left the chamber in my garage. On the recommendation of one of my Instagram followers, I let it marinate for 36 hours.
When I opened the lid, the watch looked like it was evolving into a new life form. Most concerning was a viscous dark brown sludge that had formed on one side and hung from the watch like a stalactite. It seems one of my paper clips was an inert metal, and the other was not.
At this point, I subjected the watch to a stress test, which is to say, I screwed up and accidentally knocked it off my workbench and onto the concrete floor. The movement suffered no damage, but the impact was enough to bend one corner of the shroud, pinning the bezel. Oh well. The bezel action was pretty crappy anyway, and I had no intention of trying to remove the retaining screws at this stage. Chalk it up to “character.”
I washed and brushed and buffed it once more. Like the Gatorade goop, the paper clip sludge didn’t seem to have any ill effect. Things were really progressing beautifully. The shroud had developed an effect similar to marble, with overlapping swirls and the occasional flecks of gold and veins of blue and red. This was where I wanted it. Phase 2 of the Bronze Tuna Shipwreck Patina Project was complete. Well, on the case anyway.
The buckle, on the other hand, needed more work. The same treatment that produced such a wild effect on the case produced a brown crust that had little variation and no interesting spotting underneath. It just looked dirty.
I rubbed it out with straight vinegar to knock down the brown and gave it another go in the fuming chamber, this time using the small one I had started with, again on soaked paper towels, but this time sitting on a rock because I wasn’t about to risk another oddball reaction.
I spritzed it with droplets of water, salted it with coarse-grain salt, and sealed it up in the sun for just a couple of hours. That was all it needed. It came out with droplet spots and the bluest blue bits I had seen yet.
It was time to stop the treatment because I noticed the surface texture was changing. It was noticeably rougher than the case, and there was some pitting on the underside. I think the vinegar was finally taking its toll; however, the effect was right on target. It was a good time to stop.
Content with the results on both the case and the buckle, I moved on to phase 3: liver of sulfur. This comes as a concentrated gel and is a common tarnishing agent. Most people use it as a dip to darken the entire watch case. I had a different plan. I just wanted to treat the very inside edge of the bezel insert where it met the crystal, kind of like it was seeping out.
For this step, I broke out rubber gloves and worked outside. According to the label, liver of sulfur is fairly safe when used in a ventilated area and kept off of your skin. A jeweler friend who uses it on the regular warned that can cause nerve damage. I like my nerves just the way they are, thank you very much, so I proceeded with caution. Besides, the stuff smells like ass. You don’t need that in your home.
Liver of sulfur works best hot. It’s not a great idea to heat your watch, so you heat the water instead. The hotter, the better since I was not submerging the watch head. I added a few drops of the gel to the hot water until I got a yellow liquid that I applied with a 000 paintbrush. The solution keeps darkening the metal as it dries, so I kept a neutralizing bath on hand (about 1 cup of cool water with 2 tablespoons of baking soda) to stop the reaction. I wanted to control the effect, so I started with a weak brew and made it progressively stronger, testing it on parts that would not be visible before going to work on the bezel, and then building it up with multiple applications. Working carefully, I dabbed a tiny amount of the solution in and around the markers, always working from the inside and letting it flow naturally.
I also brushed it into the engraving on the buckle, quickly wiping it off the surface while allowing the moisture to remain in the depressions. Finally, I hit the flutes of the crown and the lower recesses of the retaining screw holes. The parts I painted were browning up, but not quite as dark as I wanted. Once I felt I had a good base, I skipped the bath and let it dry overnight.
By morning, it was clear that I needed more. I mixed up a hotter and stronger solution and set to work. This time, the metal darkened quickly, hitting an espresso color as it built up. Once I felt I had produced the “goth bezel” look I was shooting for, I dropped it into the baking soda bath. It was time for phase 4.
Having achieved the right staining and darkening, I now set about removing some of the patina I had worked so hard to apply. It may seem crazy, but I like the contrast. I also wanted the watch to look well used like the patina had built up over the years while simultaneously being worn away by constant touching. To my eye, that would make it seem even older.
My targets were the edges of the bezel, the upper edge of the crown, and the very edges of the shroud. My tools were another fine paintbrush, wooden toothpicks, a thin soft cloth (ripped from an old white cotton t-shirt), lemon juice, white vinegar, and Cape Cod cloth. That last one needs some explanation because Cape Cod is great for polishing, but the cloths themselves are kind of fat and fuzzy — great for working it over a broad surface but terrible for this kind of detailed work. Instead of using the Cape Cod cloth directly, I would wrap my clean buffing rag around a pencil or toothpick, dab it on the cloth to pick up some of the polish, and then rub it on the area I wanted to clean.
Working carefully, I was able to take the patina off the high points I had identified. The lemon juice and vinegar applied with the 000 brush worked well to lighten the flutes of the crown and the bezel triangle, which I had kind of overdone. The lemon juice also helped the head of the crown, bringing the engraving back out into view.
Dabbing Cape Cod from a cotton cloth stretched tightly over my fingertip, I worked down the touch points of the bezel and crown in a natural-looking way. With toothpicks, I rubbed out the tops of some of the numbers, and cloth pulled over the side of the pencil handled the very edge of the shroud. While it’s a subtle effect that many might not notice, I think it greatly enhances the watch’s overall appearance.
With that final flourish, I declared the project done. I’m rather proud of it. It went from a clean and shiny clone to Chuthu’s dream timer. Even with a few hiccups along the way, the bronze tuna shipwreck patina was my vision, and I made it real, right down to the last detail.
Of course, now the dial looks a little too clean, too new. I’ve got some ideas about how I might handle that. A heat gun and some of strong tea might be involved… But that is a project for another day.
