CORE-BOND / Reflow Core

Tone loss is when the wrap and core coupling is compromised either through mechanical degradation from the vibration of the string or galvanic corrosion due to the dissimilar metals used in the manufacturing. Core-Bond ™️ addresses this issue by effectively "locking" the relationship of the core and wrap wire as "one".
The buildup of dirt, skin cells and acidic content in your hands get down between the windings and effectively dampens string tone as well as starts the corrosion process of the core wire. The string isn't mechanically dead, however, the tone is compromised until the strings are cleaned which can be a difficult process to complete.
Some string companies coat the wrap wire and sometimes coat the whole string to address this issue. However, a string with an outside coating may also dampen the true tone of the string as well as eventually frey off from normal playing. Coated strings will not prevent galvanic corrosion.

With a coated wrap wire or even a completely coated string, your guitar pick, as well as your frets, act like a file and eat into the coating which then exposes the wrap and core wire to corrosive elements. In addition, covers and coatings may dampen tone as well as string output.
In most cases, many recording artists may use uncoated strings in recording sessions to maximize the full tone potential of the strings and the guitar, but opt for a coated string on stage due to touring and climate changes. A guitar tech for a touring artist will purchase dozens of sets for the tour. It is not uncommon for a tech to change strings at every location stop, the main reason is to assure the artist has a fresh set on the guitar.
However, with Core-Bond ™️ Technology, which is uncoated on the outside, they will not frey, will retain its tone longer, eliminate galvanic corrosion and increase the integrity of the string for a very long time. In some cases, our beta testers claimed that the wound strings lasted up to 1 year with no tone loss. Although it is uncommon for a guitarist to have a string on for a year, this was one beta testers result.
WHAT IS GALVANIC CORROSION?
Galvanic corrosion (also called bimetallic corrosion), is an electrochemical process in which one metal corrodes preferentially when it is in contact with another in the presence of an electrolyte. Galvanic corrosion in a wound string starts immediately after it is manufactured and even more so as it's transported and stored.
The difference in the core and the wrap metal alloy causes galvanic corrosion to occur. The same is said for the acidic content in a player's hands which seeps between the winding onto the core wire causing the core to corrode onto the wrap wire from the inside out. With Core-Bond ™️ this does not happen. Some discoloration on the outside of a string is normal over time, however, Core-Bond ™️ Technology dramatically reduces the chance of loss of tone due to the breakdown of the core to wrap coupling.
A string that may start to look bad due to tarnishing, does not necessarily mean the string is bad. It is the core to wrap coupling breakdown that is the cause for tone loss and ultimately a dead string. A brand new string can also be a dead string if the manufacturer's core to wrap ratio and coupling was not made correctly from the beginning.
With Core-Bond ™️ it is virtually impossible to manufacture a new dead string due to our bonding activation process. So you can be assured each and every set of strings has the integrity you need and want.
IF I CLEAN MY STRINGS AFTER EACH PLAY, DOES THIS SOLVE THE CORROSION PROBLEM?
No, it does not. Moisture in the air, as well as elevated temperature changes and the acidic content in your hands, attack the strings integrity. When a guitar is transported in a guitar case, there would be no way to eliminate these threats unless the guitar is in a constantly humidity controlled environment every day.
Core-Bond ™️ PROVIDES ADDITIONAL TONE AND LIFESPAN
Core-Bond ™️ Technology increases strength, eliminates the chance of core to wrap slippage and makes for a revolutionary new string design!
As a wound string is tuned to key, the core wire stretches and thins slightly, while the wrap wire does not. For this reason, most string manufacturers spin the wrap around the core under core tensions similar to pitch. As the string vibrates during use, the core wire can also thin slightly, allowing movement of the outside wrap wire to slip, which over time, will cause the coupling to become compromised and therefore the string effectively starts going dead.
Corrosion over time has the same effect. The Core-Bond ™️ process ensures the integrity of the coupling over a much longer period of time, if not for an unprecedented period of time by "bonding" the relationship of the wrap wire to the core wire.
Stabilization of tuning, the strength of the string and the loosening at the twist ending by the ball are all obstacles that need to be addressed and eliminated when manufacturing a wound string. It is virtually impossible for the ball at the end of a Core-Bond ™️ wound string to unravel. The twist lock at the ball on the wound strings become "BONDED" together once the final activation process has completed.
ASSEMBLY BONDING AND THE BLACK DIAMOND #BD6900 WINDING MACHINE
BD6900 CUSTOM MACHINES
We start out with U.S.A. high-grade metal alloy. The assembly of the string begins with the application of core wire placement and pulled to a specific tension. The outer winding material is then applied by Black Diamonds most advanced string winders in the industry. Named the BD6900, these winders are one-off specialized made machines built by Black Diamond. The BD6900 assists Black Diamond production operators to produce with precision, a Core-Bond ™️ string every 20 seconds resulting in an unparalleled and consistent product.
The BD6900 winder's computer-controlled technology allows production operators to input and monitor pull tension, speed, braking, and pitch angle to name a few of the variables available to the operator. The objective is to achieve our proprietary calculations for core-to-wrap coupling. This completes the first phase of a Core-Bond ™️ strings.
Phase-two is the most important process. The Core-Bond ™️ activation phase is to submerge the string in our proprietary treatment bath that activates the inner bonding and "bonds" the core to the wrap wire. The result is longer life, lasting tone, more strength, projection, and output. These are the highest attributes that most guitar players are looking for in a great string.
WE HAVE CHANGED THE GAME FROM THE INSIDE OUT
COATED VS. NON COATED Core-Bond ™️ TESTING IN OCEAN WATER
We took a very extreme approach to our testing. By submerging Core-Bond ™️ treated strings in a 5% Saline bath to replicate ocean water, the image below shows results after 96 hours. Keeping in mind, Core-Bond ™️ strings DO NOT have an outer coating to protect the strings. The result is amazing.
Now, we realize a player is not going to put their string in ocean water, but this does validate the protection characteristics of Core-Bond ™️
The strings were clipped at each end to show the acceleration of corrosion at the ends of the exposed steel plated core wire. Notice seepage of corroded core coming through the center of the coated string on the right, compared to the non outer coated Core-Bond ™️ treated string left .STANDARD HEX CORE vs HEX CORE with Core-Bond ™️
Above - Natural core without Core-Bond ™️
Magnification image below shows a Black Diamond's high carbon steel core and the valleys Core-Bond ™️ create. Our secondary Upflow process reflows and upFlows to locks in the wrap wire.
With the wrap wire disassembled from the core, the valleys remain. The core wire is surrounded and protected by Core-Bond ™️ . The Tips of the valleys you see show how Core-Bond ™️ , our Secondary Stage Upflow Submersion process allows the Core-Bond ™️ to up-flow into the wrap wire spaces and secures the wrap to core bonding we need to achieve.
Above - Black Diamond's high carbon steel core and the valleys Core-Bond ™️ creates
Below - Competitors less than robust attempt at core to wrap bonding.
Black Diamond Strings with Core-Bond ™️ FACTORY WARRANTY United States
Strings are subjective, we understand that players have their own view of when a string has lost its tone. At Black Diamond Strings, we are so confident in Core-Bond ™️ technology, we offer free replacements within 60 days of purchase for any string you feel tone loss is experienced. Just present us with a proof of purchase. (At this time, replacements are available to USA customers only)
PATENT - US9424819B1 - Corrosion-resistant wound musical string. Abstract - The method improves the core wire-to-wrap wire bond by using a bond coating between the core and wrap wires that preferably also minimizes the galvanic activity between them. The bondable coating is applied to the core or wrap wires, or both. In one embodiment the method entails creating a coated core wire by annealing bare core wire, bathing the bare core wire in a bondable coating material and removing any excess, drying the bondable coating, making the string using the bondable-coated core wire, and reflowing the bondable coating. In another embodiment the method entails additionally coating the wrap wire with a coating that does not reflow under the same conditions as the bondable coating on the core wire, and winding the coated wrap wire around the bondable-coated core wire before reflowing the bondable coating.
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