-Making Mokume-

Knife with Sterling and Copper Mokume, J. Loose, '00.


-Mokume-

Mokume is a natural extension of an interest in damascus. Both are fusion-layered patterned laminates. 'Mokume,' translates from the Japanese as '...wood grain,' and is the same word used to describe pattern-welded steel. It is made in a similar fashion; alternating layers of differing non-ferrous metals are laminated and manipulated to reveal the underlying structure. This versatile material can be utilized in many ways as any non-ferrous metal: it can be cut, soldered, raised, formed and carved. It cannot be cast, as melting would destroy the inherent separations of differing metals.

-Introduction-

This article is intended as an introduction to making Mokume. It is geared toward the Blacksmith / Bladesmith and their tools & equipment, rather than the Jeweler, in whose studio the Ironworker finds a number of unfamiliar contraptions...

I strongly recommend Steve Midgett's book / video available at Mokume.com
Mr. Midgett's book includes an excellent Mokume kiln that is easily constructed. It also features an excellent section geared toward the bladesmith's shop. GET IT.



The method described below is one of the least controlled processes for making Mokume. A forge with accurate temperature controls is essential. I have an upright forced air D.Fogg style forge with a hole in the top for a thermocouple. I can control my temps from 1400 F to 2200 F. The thermocouple and display came from Grainger, or you can use 'Tempil-sticks,' available from MSC. Tempil sticks are basically crayons that melt at specific temperatures.

An addition to the process described below is the use of stainless steel tool wrap. I recommend this step when using precious metals. Enclose the bound billet in the tool wrap filled with clean charcoal powder. This will facilitate a very reducing atmosphere but requires a longer soaking time in the heat source environment.

A forge with good temperature control can work with the following information, but a heat treat or burnout kiln will work better.

-Materials-

Almost any non-ferrous metal can be used to make Mokume. Some work better than others and some are affected by close proximity to other metals- for example silver and brass do not fuse well but may be separated by a layer of copper and the whole billet fused quite successfully. Copper and high copper alloys add malleability. Metals with low melting points such as bronze create difficulties in uniform fusion with high melting point metals. Silver and gold both work well in addition to several Japanese alloys to be discussed below.

Mokume Compatible Alloys
(In order of melting points.)
Alloy Melting Point Composition
Copper 1981 F / 1083 C 99.9 Cu
Shakudo 1952 F / 1066 C 75 Cu / 25 Au
24K Gold 1945 F / 1063 C 99.9 Au
Fine Silver 1761 F / 960 C 99.9 Ag
Shibuichi 1720 F / 937 C 75 Cu / 25 Ag
Brass 1710 F / 930 C 65 Cu / 35 Zn
Sterling Silver 1640 F / 893 C 92.5 Ag / 7.5 Cu
14K Gold 1615 F / 879 C 58.5 AU / 41.5 CU

Untracht, p. 373, abridged.


Shakudo and Shabuichi are two Japanese alloys used in Mokume, among other things. Shakudo is a mixture of 75% copper ( Cu ) and 25% gold ( Au ). It can be depletion gilded, a process wherein the surface copper is removed by chemical means, leaving a thin layer of pure gold. It also has unique patination properties. Shibuichi ('misty-silver') is a mixture of 75% copper and 25% silver ( Ag ). Shibuichi, like Shakudo, also has unique patination properties.

-Methods of Fusion-

There are two methods of fusing the layers that make up Mokume: wet-bonding, or sweat soldering and diffusion weld bonding, or a fusion process much the same as ferrous forge welding. Most Black / Bladesmiths will probably find the diffusion process more familiar although it is slightly more difficult than wet-bonding. Diffusion also offers a stronger and more malleable Mokume capable of greater manipulation and hence, greater pattern and form possibilities.

-Making the Billet-

First select the various alloys you wish to use in your Mokume billet. There are several considerations to take into account. Firstly make sure that your alloys fall within a relatively close range of melting points; if you are wet-bonding make certain that your solder falls below the melting point of all the alloys in use. The secondary consideration is the order of the alloys in question... this is primarily an aesthetic decision but you may also wish to take into account placing together metals that will fuse / solder easier. Lastly, a similar thickness of each layer is traditional and easier to work with, though not absolutely necessary.


Alternating layers of Silver and Shibuichi- very subtle Mokume.

Each layer must be of the same length and width- in the example above pieces are 3" x 1". Each piece must be as flat and as clean as possible. To flatten sheet metal place it on a polished steel surface and strike with a rawhide or high-density plastic mallet. The sheets should then be freshly sanded and wiped clean with acetone or denatured alcohol. You will need two steel plates at least 1/4" x the size of your layers- in this case 1/4" x 3" x 1". The surfaces of the plates contacting the billet should be coated with yellow ochre mixed with water and applied as a paste. Gently heat the plates to dry the yellow ochre. This is to prevent the Mokume material from fusing to the steel plates.

As a note: yellow ochre is commonly available through artist's paint supply houses. It is basically clay and quite safe to burn. A workable substitute is 'White- out,' or similar products, although the fumes are -dangerous-.


-Preparations for Diffusion Welding-

This process is very similar to making a steel Damascus billet. I am going to present the method most easily undertaken in a typical bladesmith's shop. A forge with accurate teperature / atmosphere controls will work but a heat-treating kiln or jeweler's burnout kiln will work better. See bibliography for further information.

Assemble the layers in the desired order, maintaining absolute cleanliness of the surfaces. Freshly sanded and cleaned with alcohol or acetone is sufficient. Place the Mokume layers in between the steel plates, with the ochre coated sides against the Mokume. These plates must be of the same dimension as the billet in length and width as their primary purposes are to prevent the layers from shifting during heating and fusion thus maintaining an oxide-free contact between the layers. Clamp the whole assembly in a strong vise and bind with heavy steel wire as shown below:


An airtight pressure upon the layers is critical as oxidation inhibits fusion.



-Welding the Billet-


The bound billet placed in a low-temperature reducing atmosphere.

When welding the main issues are the prevention of oxides and overheating. A Mokume made up of primarily copper-based alloys will fuse between 1400-1900 F. Silver, if present, will fuse at a much lower range: 1100-1400 F. You want to set your temperature to approximately 50 degress F below the -lowest- melting point in your billet. It is quite easy to melt and ruin the Mokume when heating in a forge. Maintaining a reducing atmosphere and proper temperature is critical in either a gas forge or a coal forge. A kiln with accurate temperature controls is the ideal heat source.

A further precaution is to enclose the billet in stainless steel tool wrap filled with clean charcoal powder. This creates a very reducing environment and will catch any material that melts in the event of over-heating. It requires a longer soak time and is better done in a kiln.

In the case of an un-enclosed billet, heat slowly to insure evenness and watch for a red-orange color- when this is achieved the layers are at the proper temperature. In the case of silver layers they will fuse when they 'sweat,' or appear on the verge of becoming fluid. Remove the billet and -gently- apply pressure by tapping with a light hammer. If the temperature is too high or the strike too hard you will squeeze near molten metal from between the layers.

When the billet has cooled to black, remove the binding wire and the plates.


The material may appear quite rough before filing the edges and forging/rolling flat.



-Manipulating the Layers-

At this stage the billet may be used or further manipulated to create more layers and affect surface patterns. First, the billet must be cleaned up- file the edges square and make sure you have a solid weld. If you notice any cold shuts you can coat the piece in a high temperature paste flux such as Prip's or Handy Flux and return to the fire; heat and forge again.

Those of you familiar with Damascus work will need no inspiration. Non-ferrous metal can be cold-forged, although some recommend forging Mokume at a very dull red or very hot black heat ( around 900 F). The primary concern when cold-forging is relieving the metal of internal stresses by annealing it. To anneal most non-ferrous metals heat them to a dull red and quench when the redness disappears... however, with Mokume quenching can cause weld-shear due to differing rates of expansion / contraction. Simply let the billet air cool in between courses of forging. I do a great deal of my cold-forging on a treadle hammer; treading very lightly as it were. A jeweler's rolling mill is a great boon in this endeavor, but hand forging will teach you patience, if nothing else.

You can increase the number of layers by forging out, cutting and restacking. Weld as before.

The traditional wood-grain patterns are what Bladesmiths call 'Pool and Eye,' but the method of producing the pattern is a little different. Rather than drilling holes and forging flat the Mokume is forged into a sheet and a ball-pien hammer is used to make dents on both sides. These dents should produce bumps on the reverse side. The whole sheet is then sanded smooth. But basically anything you can do with Damascus you can do with Mokume, including composite construction and mosaics.



-Bibliography-

Midgett, Steve. Mokume Gane Available at Mokume.com

Untract, Oppi. Jewelry Concepts and Technology. New York: Doubleday, 1985.
Very comprehensive and contains more controlled procedures for the more advanced artisan.

McCreight, Tim. The Complete Metalsmith. Worcester, Mass: Davis Publications, 1982.
Very good introduction to non-ferrous metalwork. Also very good with improvising tools and equipment.

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