Stonewash – what is it and what is it for

Stonewash – one of the most popular modern methods of processing the blade. It is used everywhere, by almost all major global manufacturers, and is popular among knife enthusiasts, as one of the available ways to independently customize knives. The term stonewash itself is synonymous with tumbling. Tumbling is the hardening of the surface layer of metal by its point deformation in the environment of various granular materials. It is a mechanical treatment of the surface by mixing with a special tumbling filler containing abrasive material. Tumbling can be used both for grinding and for polishing surfaces made of a wide variety of materials: metals, glass, ceramics, natural stones, wood, etc. With this technology, it is possible to clean the workpieces from sinter, burrs, rust, carbon deposits, and to improve the surface quality.

Industrial stonewash

Surface treatment can be carried out on various equipment, the most common are tumbling barrels and special vibration machines. In rotating barrels, the processed part is located among the tumbling bodies, and due to the rotation, they cause micro-impacts on the surface of the workpiece. When vibrotembling, the movement of the workpiece and the tumbling bodies is created by vibration, which mixes the entire contents of the barrel at a certain speed.

Tumbling barrels are the simplest type of tumbling equipment. The barrel can have a cylindrical or polyhedral shape and be positioned horizontally, vertically, or obliquely relative to the axis of rotation and is driven by an electric motor. Tumbling processing is carried out due to the free mixing of products and tumbling bodies at rotation of the barrel. This is the most inexpensive and widespread method of tumbling. It has a number of disadvantages: low processing speed in comparison with vibro and rotary tumbling machines, too rough processing of thin delicate blades, high noise of the tumbler machine.

The tumbler vibrating machine is by far the most popular type of this type of equipment. Inside the machine, there is a working area in the form of a barrel, bath, or pipe with an attached vibration drive. Parts and tumbling bodies are mixed into the working area. With the help of an electric motor, oscillatory movements are applied to the working area of the machine. Currently, a huge number of vibro-tumbling machines of various sizes and designs are produced. They are characterized by high speed and the ability to handle knives with a thin blade more delicately than in tumbling barrels.

In addition to the barrels and the vibrating machine, the tumbling can also be carried out by a rotary machine with a fixed working chamber and a rotating plate with blades. As well as a machine with a rotating spindle, or a special belt machine. But these methods are by far the most expensive and rarely used in the manufacture of knives.   

According to the method of processing parts, the tumbling is divided into dry and wet. When dry tumbling inside the barrel is not added liquid and used dry tumbling bodies. When wet tumbling in the barrel enters the buffer solution or working fluid. When processing metal parts, mainly wet tumbling is used. In it, the key role is played by the so-called "compound" (technical shampoo) - a chemical composition consisting of inhibitors, coagulants, and stearin. These chemicals affect the cleanliness of the surface after tumbling. The compound is selected individually, for each type of workpiece. A liquid compound made on a soap base is used for tipping the blades of knives. Compounds for stainless and carbon steels differ in their composition.

The most important role in the process of work is played by the tumbling bodies, the so-called "chips". Different materials can act as such bodies. Most often they are divided into ceramic, porcelain, and plastic. The shape of tumbling bodies also differs in variety: they can have the shape of a prism, pyramid, cone, cylinder, or ball. When processing metal, materials can be used as tumbling bodies and without a bond: natural stones, walnut shell crumbs, wood, and others. When choosing a filler, it is necessary that it penetrates into the most inaccessible parts of the blade (inside the groove, in the sub-finger "choil", the place of transition of the blade to the ricasso, etc.). Therefore, when tumbling the blades, bodies of different sizes and shapes are used.

DIY stonewash on the blade

In addition to tumbling blades at enterprises, stonewash is widely used when creating your own custom blades at home. Most often, this applies to the blades of folding knives, which can be processed by separating them from the handle. In manual tumbling at home, as tumbling bodies, natural stones are used (pebbles), expanded clay for flowers, stones for aquariums, walnut shells, etc. The blade for tumbling is placed in a metal or plastic container filled with tumbling bodies, as a compound is often used WD-40 (contains the white spirit and mineral oil).  A closed container with such a composition is simply shaken by hand for 20-30 minutes. In this way, you can achieve a light stonewash effect. To obtain stronger traces on the surface of the blade, such a container can be placed in a closed-form in a washing machine and scroll the container at low speed for the required time. A more rigid version of home stonewash is the use of hardened metal balls from the bearing. Tumbling by this method gives the coarsest coating and can lead to deformation of the blade, but at the same time due to the uniformity of the shape of the tumbling bodies and the possibility of having a very different dimension, it is in this way that you can get the most uniform surface.

For manual home tumbling, it is also possible to use a small rotary tumbler machine. They allow you to change the speed of rotation of the barrel, but they have a very limited internal volume. And most often they are suitable for processing only a few small blades at a time.

Tumbling of the blade improves its appearance, gives the knife a certain "brutality" and charisma.  And most importantly, this method of processing the blade is affordable for every knife enthusiast, allowing you to customize any knife with minimal time and money.