Whether You Call It Copper San-Mai, Cu-Mai, Or Anything Else, Copper Damascus Is One The Trendiest Ways To Forge Knives Today.
By now most knife enthusiasts are familiar with pattern-welded steel, commonly called damascus, whose re-invention for use in knife blades is attributed to BLADE Magazine Cutlery Hall-Of-Fame® member Bill Moran.
The damascus world has since exploded with complicated mosaics, exotic-tiled canister billets, and, more recently, even some interaction between pattern welding and 3-D printing. These new techniques are mind-blowing for sure.
Copper San-Mai
One of the hottest new trends in damascus is the inclusion of copper into pattern-welded billets. Commonly called copper-mai, copper san-mai or cu-mai, the technique has been brought to near perfection by Coy Baker at Baker Forge & Tool.
In 2019 at the request of a customer, Baker created his first copper damascus billet. Starting with Baker as a one-at-a-time weekend garage craftsman, the business exploded. Baker Forge & Tool now has a 3,000-square-foot shop and 10 employees, and they can’t keep up with demand.
Baker says the welding of copper in stacked configurations has been around for centuries in the form of mokumé gané, aka mokumé. While he’s the first to blow up Instagram with welded copper damascus, he is certainly not the first to attempt the cu-mai technique.
He primarily uses 80CrV2 carbon steel for the cores of his billets, and also various patterns of a damascus of 1080 carbon and 15N20 nickel-alloy steels. ABS master smiths Steve Schwarzer and Jason Knight helped him along in his early damascus-making journey.
How To Forge Copper Damascus
To forge a copper damascus billet, Baker typically uses a core of 80CrV2, a layer of 20-gauge pure copper shim stock, and a cladding of 1080/15N20 damascus.
“It’s important that the core and cladding stay in a 1-to-1-to-1 thickness ratio,” he said. “The copper doesn’t harden, and it’s critical to keep the core centered so that the cutting edge of the knife will be hardenable steel.”
He hasn’t experimented with copper alloys other than pure copper, though he has used some bronze and nickel with good results.
It’s no surprise that there are trade secrets that Baker didn’t volunteer, and I was polite enough not to ask. Copper stacked in a billet oxidizes quickly, similar to stainless, and so the welding must be done very precisely. For the welds to stick, the surfaces being welded also must be exquisitely clean, with not even a trace of oils or fingerprints.
The Different Types Of Copper Damascus
Baker did reveal that there are two basic versions of the process. In one, the layers are welded around the perimeter as in canister or stainless welding, and then the entire billet is welded at once. In this method, the temperatures are enough to liquefy the copper, and the perimeter welding keeps the liquid in.
In the other version, the billet components of core, copper and clad are stacked together and held at brazing temperature. This is Baker’s preferred method, as the copper doesn’t liquefy and so performs more consistently when it comes to thickness. Such exact brazing requires precise temperature control, as a 10-degree variation in either direction from the proper brazing temperature can produce failure.
While there are no doubt smiths who have attempted and maybe even successfully welded copper damascus by hand, Baker acknowledges that the aspiring smith is much more likely to be successful using a press or power hammer to set the weld. Precision temperature control also gives increased chances of success.
Dion Damascus
While Baker is the best known and most common source for copper damascus, another variation is available from Dion Damascus. Florida knifemaker Andrew Mochado recently made a knife from a bar of Dion Damascus that included brass, copper, and nickel clad over a core of 52100 carbon steel.
“It is my take on a gyuto-style chef’s knife,” he said. It has a box elder burl handle with an ebony bolster. Mochado heat treated the blade in a gas forge. “The outside layer of the billet was nickel, so it was very difficult to get it all up to temperature,” he explained. “The nickel buckled up a bit and I thought I had a failure. I was able to successfully grind off all the buckling, and the blade was still perfectly forged together.”
Baker pointed out that the melting points of copper and nickel are above the heat-treating temperature of carbon steel. However, in a forge, the outside layers come in contact with a forge atmosphere that’s well above the desired hardening temperature, thus causing problems with the non-ferrous layers.
How The Copper Affects Knifemaking
Jordon Berthelot is a Texas maker known for kitchen knives and intricate carved and sculpted blade plunges. He’s also made dozens of blades with Baker’s cu-mai. He has been Coy’s “guinea pig” for testing new patterns for months. When Baker develops a new pattern, Jordon builds the prototype.
“I’m pleased with how the cu-mai grinds. You might expect the copper to be gummy or soft or to grind differently when you sculpt it, but it pretty much grinds the same as steel,” Berthelot observed. “You always have to pay attention to get the carving right, but the copper poses no problems.”
Makers will notice the copper being softer if they hand-sand it aggressively, but overall the copper layers are no more difficult to finish than regular steel.
When it comes to finish work, Berthelot recommends sanding to at least a clean 600 grit prior to etching. “Regular” ferric chloride doesn’t perform well, and etching copper in it will leave a copper tint on standard damascus steel blades later. Instead, Berthelot prefers a 20/20/60 mix of ferric chloride, muriatic acid and distilled water. The addition of the muriatic acid keeps the copper from looking blurry, and keeps the material out of the solution for future etching. After the etch, Berthelot buffs with “black magic” rouge so the copper will “pop” nicely.
Forged in Fire season 1 episode 2 “OG” winner Chris Farrell of Fearghal Forge in Austin, Texas, took advantage of the bold copper line in his piece of Baker Forge damascus. The copper makes a dramatic, bold statement, and so do the curves and lines of Farrell’s fancy faceted fighter.
“People see my faceted handles and think they’re kinda funny until they pick one up and realize how well it fits their hands,” Farrell said. He is fascinated by innovations in the knife industry and is always looking for his own ways to innovate. He’s experimented with forging Baker’s copper damascus bar stock: “It can be done, but you really have to be careful. It’s real easy to mess up!”
Copper Damascus Around The World
The cu-mai trend is not limited to the United States. Australian knifemaker Adam Fromholtz of Canberra crafted a cake knife of copper damascus from the Japanese steel company Takefu. Takefu steel can be a challenge to find in the USA, but there is a reliable Australian distributor.
Adam’s blade is copper, nickel and brass clad over a V-Toku-2 carbon core. Regarding the steel, Fromholtz noted that it was near impossible to forge due to the differences in ductility between the materials. Because of the softer cladding, he noted that the blade tends to gall a bit, so makers should take note of this when fitting a slotted guard on a blade of such a material. Overall, the steel is simple to finish but shows handling marks easily.
How Do Copper Damascus Knives Perform?
Is copper damascus all flash and bling or does it perform? Copper does not harden the way steel does, which makes you wonder how it impacts knife performance. First of all, copper damascus is used with a monosteel—that is, one layer of steel—or a regular carbon damascus core.
Using a steel core makes it where the copper has absolutely no impact on the blade’s cutting performance, edge stability or toughness. Baker said he knows of two makers who have used his cu-mai material to complete American Bladesmith Society-style performance tests of rope cut, 2×4 chop and 90-degree bend.
When it comes down to it, the copper layers are very thin. Considering that the final weld-up of clad/copper/core/copper/clad may be as much as 2 inches thick, and that the copper starts out roughly .03-inch thick, the overall final billet has very thin layers of copper. It’s enough for a dramatic pattern but not enough to impact knife performance in a negative way. “I made a knife with it then beat the hell out of it,” Farrell said. “So long as it’s heat treated properly, it’s good stuff.”
Availability Of Copper Damascus
If you’re a maker looking to capitalize on the copper damascus trend, get in line. Baker Forge releases approximately 70 billets a week to the public, in addition to what it produces for commercial use. The billets “drop” Saturdays on Instagram and are usually gone by the end of the day.
Most billets are 2-2.5 inches wide and come in thicknesses from ⅜ inch all the way down to 3/32 inch. Pricing currently runs up to $25 per linear inch, but as in all things post-pandemic manufacturing, the supply costs for raw materials keep increasing.
As for consumers, check knife shows, magazine stories such as this one, and Instagram and elsewhere on the Internet. Cu-mai knives are out there—you just might have to do some digging to find them.
Read More
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- The Many Moods Of Mosaic Damascus
- Feeling Good: 4 New Handle Materials
