This is the first of several reports on the basic information, the basic knowledge, of minting coins and medals. These facts are so important they should be embedded in the repertoire of everyone associated with the medallic field and, certainly, everyone within the firms which make these.
EVERY coin and medal struck for the last 2,650 years – since the first coin was struck in 640 BC – exists because of one technique: engraving. Creating the lines and cavities in a die to reproduce a design in objects struck from that die is the result of engraving.
The surface containing the relief design rises and falls from a background is a special form of three dimensions called bas-relief (the “s” is silent, its pronounced baa-relief). I prefer the term modulated relief for the images of devices and lettering of varying height shown on that surface.
Die engraving over time has evolved through three stages. For the first 2500 years the only method to create those dies was for a skilled craftsman to hand engrave them — to carve away little portions of the surface of iron to form a completed die. By the use of hand tools he crafted a die with cavities the exact size of the object to be struck from that die.
Because this work was tedious, mechanically inclined craftsmen sought a method to mechanize the hand work. A progression of instruments were developed, the most successful were those that cut a die from an oversize pattern, in effect a die-engraving pantograph which cut the surface of the die from a much larger pattern.
The large pattern from which the die is engraved was created by a sculptor, who in effect, replaced the hand engraver. The pattern was mounted in a reducing pantograph by a craftsman who set the machine to operate. With an electric motor it operated unattended cutting a die any size desired. Also the pattern could be used again so several size dies could be made from a single pattern. Or it could cut a hub or master die from which many dies could be made.
At first it was the central design, the device alone, which was modeled as the pattern to cut into a die. Lettering and stars or ornamentation was added later, by hand punches. It was not until 1899 that a French inventor, Victor Janvier, patented his die-engravng pantograph that could cut the die entire, lettering and all. His “Janvier” machine dominated die engraving for the entire 20th century.
With the 21st century we see the rise of computer engraving. The image is entered in a computer as X and Y coordinates for height by width. The depth of the image is the Z factor. Three factors at each point of the image, and as many points as the resolution of the image requires. This data is then fed into a controlled milling machine which cuts the entire surface image into the die in the size die required.
- Hand Engraving Only method of engraving for 2500 years, still used infrequently at present.
- Die-engraving Dominated all die making 1900-2000; cutting Pantograph devices alone at first, then entire sides, everything at once.
- Computer Engraving Increasingly used to cut dies to be major technique following year 2000.
Cutting a die by hand is called hand engraving. Engraving dies to be used in striking is called diesinking. Engraving dies by use of master punches is called hubbing. Engraving by various mechanical implements is called machine engraving. And now we have COMPUTER ENGRAVING.
Engraving an existing item – a medal say – to personalize it after it is struck or cast (as name of a recipient) is called inscribing. One “engraves” a die, but “inscribes” a medal.
Die engraving is different from “engraving” found in most reference works, which refer to the preparation of printing plates for prints or paper money; we call this flat engraving (as for line or surface engraving). This engraving has no relief. It creates two levels of surface: one surface that prints and one that does not.
During the 19th century “engraving of dies” and “diesinking” were considered the same, synonymous (and listed as such in trade directories). Later in that century diesinking came to mean hubbing of dies. These terms now all have more explicit meanings, all within the required duties of the engraver and the overall concept of die-making.
Die Engraving Overview.
Engraving of dies was always done in iron before the development of steel (and always in steel afterwards). Iron and steel have the amazing property of being hardened and softened at will by heat treating. Thus the engraver can cut the design in soft iron, it can then be hardened and thousands of impressions can be made from that iron die.
Engraving of dies is considered a form of carving, cutting away small bits of metal to form the relief design. More often than not, this is negative carving to strike positive objects. But some hand engravers are so skilled they can carve positive – called CAMEO ENRAVING – or negative with incised cavities.
The engraver must know his tools (see list). These implements are also made of steel, but obviously are harder than the iron DIE BLANK the engraver is cutting. These tools create the lines and cavities that reproduce the relief design and lettering by creating modulated relief surface.
Burin. An engraving tool with a diamond or lozenge shaped cutting edge, often used for engraving lines, lettering or fine detail in dies.
Burnisher. The tool for polishing the surface of metal; made of metal or stone, a burnisher smooths a metallic surface to effect its polish.
Chisel. A tool, flat and pointed at the end, used by engravers to handcut a die, or by chasers in their work.
Engravers’ Ball, Engravers’ Block. A vise to hold a die or medallic item while some form of hand work is performed on it – engraving, chasing, inscribing, proof polishing or such.
Graver. A cutting or shaving tool used by an engraver to handcut metal (as a die or flat engraving).
Milgrain Tool. A beading tool with a wheel of hemispherical cavities that leaves a trail of precisely and uniformly formed beads.
Oil Stone. An abrasive stone for sharpening engraving tools, a whetstone.
Punch, Puncheon. A tool made of steel containing a letter, figure, dentile, ornament or a part of a coin or medal design used to press into softer steel to make a die, or to counterstamp a numismatic item.
Spitz, Spitzstick. A pointed graver; an engraving tool with a long sharp pointed end.
Transfer Wax. Wax in ball or sheet form used by engravers to transfer a drawing, design or lettering to the surface of a die to be hand or machine engraved, or to the surface of a medal to be inscribed.
Basic die engraving techniques.
The engraver is responsible for the steel he must use and the preparation of a blank die he must make into a suitable die. The choice of the steel is most critical. The best iron or steel available must be employed, otherwise in use the image will sink during prolonged striking, or worse of all break, starting at an edge.
Prior to 1756 all dies were made of iron; in that year an English manufacturer, Benjamin Huntsman (1704-1776), invented a method of making crucible steel that proved most useful for dies. Matthew Boulton used Huntsman’s steel for the dies at his 1790 Soho Mint and the mints throughout the world used Huntsman steel for a century and a half – until 1950!
Steel for dies is ordered from steel manufacturers by type of steel, diameter, hardness, and whether oil or water hardened. It usually is supplied in long rods called bar stock, although other shaped stock has been used for dies, as square or hexagonal. (Round is ideal for many steps in making and using a die, turning on a lathe, locking in the press, and as a final point, orientation of the obverse and reverse properly.)
The bar stock is cut on a band saw to approximate height of the finished die. Next it is milled smoothed and both ends made exactly parallel. The working end where the design is to be cut is polished. If the engraver does not do this, then it is done by a tool and die worker, a separate person in a large mint or medal plant. At this point it is a die blank, ready to be engraved by any method, hand or machine engraved.
Laying out the design for hand engraving.
The surface of the polished die blank is next coated with Chinese white, a watercolor paint. An engraver will wet the tip of his finger and spread an even coat over the entire surface to be engraved. It dries quickly and the design can be drawn with a pencil right on this white surface. (Or the engraver may use dye blue if he wishes, but in this case he must inscribe the design with a sharp pointed spitzstick or scriber.)
What the engraver draws is an outline of the intended design. This is called a cartoon. (One might think this word was named after comic cartoons but it’s the other way round – die engraving cartoons came first.)
The engraver can actually draw an original design right on the die. He will include lettering in its proper place in addition to the main device and all subsidiary devices – stars, dentiles and whatever else. Including too much detail at this point is not necessary as this surface will be removed for the most part before he gets to these.
Or, if the engraver has an exact size cartoon on paper, he can transfer this pencil drawing to the white coated die surface, called design transfer. This is accomplished by coating the back of the paper with graphite, laying this on the coated die and tracing the design. (This technology was used before carbon paper was invented, which, of course, could be used.)
If the engraver wishes to transfer an incuse image, say from another die, to an uncoated fresh die he fills all cavities with precipitated chalk, wipes off the excess, lays on this a thin sheet of transfer wax, places this on the bare die, and burnishes the back of the wax sheet with a burnisher.
At this stage occurs what everyone typically attributes to an engraver – removing tiny bits of metal to form the design in modulated relief. The cartoon indicates where most of the unwanted dead metal is to be removed, mostly background cutaway. Formerly this was done with hammer and chisel, modern engravers now have pneumatic gravers that remove gross metal from the die surface in quick time with less muscle power.
At this point the engraver does not worry about the ridges left from the chisel or graver, however it is quite critical how deep he carves. The depth of this cutting will ultimately be the background or field of the piece struck from this die. The tool marks are removed by later lapping or stoning.
Then he turns his full attention to the main device. Here is where he cuts the modulated relief of the design with burin or graver. Each tiny bit of metal removed is called a bite. His skill and talent come into play in carving the portrait or feature of the design. The engraver must be an artist at this stage employing all his artistic ability. He is creating a miniature relief by sculptural carving, often in the negative.
He holds the burin or graver in the palm of his hand with his index finger lying along the shank of the tool. He points with this finger to where he wants to cut. He pushes with his hand down into the metal and scoops out a tiny bit of metal. This action is called palm push because the palm of the hand pushes on the handle forcing the point of the tool into and up out of the metal die surface.
We have assumed here the artist is cutting intaglio, carving the relief design in the negative for all the above. However, the artist can cut cameo, in the positive. Cutting a positive cameo die eliminates the need for frequent proving. The image is always in view. The cameo die has another advantage, it can serve as a device punch to hub into the working die.
Carving and using punches.
Before 1950 there were commercial punches of letters and figures engravers could obtain from typographic houses (which made type for letterpress printers – the rise of lithographic printing however made all letterpress obsolete and type houses went out of business). For most engravers the desired type, style and size, it seemed, was never available. Thus the engraver had to carve new punches for the correct lettering style and size he was seeking.
Imagine a letter on the end of a pencil point. In a sense, this is what the engraver must carve, exact size, and a different one for each different letter. (Thank goodness he can use the same “E” punch or any other repeated letter over and over – he only needs one for each letter.) It is “carve away” engraving to make a letter or figure punch and the final punch must have a sloping contour with a proper bevel, often turned on a lathe.
The layout for lettering will have a guide line or base line drawn or lightly inscribed on the face of the die where the bottom of each letter must appear. He may also inscribe a second guideline for the top of the letters. He does not punch the letters in order they appear on the die; instead the engraver most likely will choose a letter with a flat base, as an “E” to start (where top and bottom must line up with the two guide lines). Each letter is punched into the die individually.
When punching the lettering the engraver must be aware of four things at once: (1) the letter must rest on that base line, or fit precisely between the two if there are two guide lines, (2) he must not tilt the letter, it must be upright, exactly perpendicular to the base line, (3) he must be aware of interletter spacing [“IE” should be further apart than say “OO”], (4) he must sink the punch to the same depth as all other letters. The last is most important because an “M” requires more pressure to sink than an “I” for example.
To insure correct positioning the engraver lightly taps the letter punch to get a faint image on the surface of the die. If it is correct in all respects, he replaces the punch – it must “seat” in that same impression – and taps the punch to the proper depth. If it doesn’t seat properly, or he moves the punch between blows, he will create a double image for that letter. Punching letters and figures requires experience; lettering by an amateur engraver, who perhaps cannot control all four requirements at once, is very obvious on the struck piece.
Diesinking and hubbing.
The engraver does not have to engrave every element on the face of that one die blank (although he can if he so desires). He can carve separate elements and bring them together by sinking them into that master die blank. He can engrave the device separately (even in cameo) making it a device punch. By diesinking he can get that image into that die; obviously it is too much to sink it by hammer blow, he must hub it by using a press, a screw press – or for even greater pressure a hydraulic powered hubbing press – to impress the device punch into the die.
The device punch must be hard and the die blank must be soft, thus heat treating is important at this stage. The two – punch and die – are positioned in the press and are squeezed to drive the punch into the die. Often a retaining ring is necessary to hold the punch in position during hubbing (creating this tube-like collar is the responsibility of the engraver or tool and diemaker). This is the hubbing function of diesinkning.
Hubbing always changes polarity. A positive punch creates a negative element in the die. The device punch carved cameo is ideal for pressing into the negative die. The negative die, then, can be used for striking. Or, instead it can become the master die and a hub can be sunk from it. Then working dies can be made from that hub. By the process of hubbing the engraver can go back and forth with a change of polarity each time. Multiple working dies are necessary for long production runs. A master die is “insurance” that another die can be easily sunk if the one in use breaks or deteriorates.
At any step along this process the engraver can examine the state of his work by proving. He can push soft material, clay or wax, into the die cavity or the surface of the die to give a quick look. For more detail, which is usually the case because the engraver is working on tiny areas of carving, he will want to make a metal proof. These can be a hot tin impression, called a splasher, which he can do right at his workbench; or a lead proof if he places the die in a press and softly impresses the lead.
The closer the engraver gets to the finished die, the more proofs he will make. He seldom makes any proof until well into the process. He usually does extensive carving in the die, then he makes a proof to check on his progress. This continues until he is completely satisfied with the total image. He will then harden the die and it will be ready to be placed into production.
Use of Sculptured Patterns in Engraving.
In an attempt to relieve the tedium of hand engraving, engravers and mint workers looked to the pantograph, the die-engraving pantograph, to aid in cutting dies. In constant development from its early crude form for nearly 150 years, these machines were in use at mints in Belgium, France and England. It required, however, a pattern in hard material to reduce the image while it cut the relief.
Engravers and mint officials turned to sculptors and wax modelers to create these patterns. It was not, as some believe, a model for the engraver to handcut the image in reduced size, but rather a three-dimensional surface that could be reduced by stylus tracing and mechanical pantographic reduction.
What the sculptor created was a bas-relief – a design of modulated relief attached to a solid background. Sculpture in wax was ideal, as well as those in clay and other media (the use of plaster of Paris came later). However, this had to be converted to a hard surface of the image for the stylus to trace over. These were cast in metal, iron was the first to be used, later copper was found to be more ideal for the stylus to ride over.
The first sculptor to prepare a bas-relief for medals in America was Ferdinand Pettrich (1798-1872). In 1841 he created a relief portrait of President John Tyler in wax for the Indian Peace Medal Series. At the U.S. Mint Franklin Peale (1795-1870) cast this in iron and used it to cut three size DEVICE PUNCHES of the 1842 Indian Peace Medal (on the Philadelphia Mint’s newly acquired Contamin pantograph, well suited for cutting multiple size hubs from the same pattern). Each of these device punches was sunk into an appropriate size die blank and lettering added by punches.
Sculptor Pettrich’s presidential portrait was followed by John Gadsby Chapman (1808-1889) who furnished President James K. Polk’s portrait in 1846 for the same series. In 1849 Henry Kirke Brown (1814-1886) created Zachary Taylor’s portrait, but these portraits were surpassed by Millard Fillmore’s, Franklin Pierce’s and Abraham Lincoln’s portraits by Salathiel Ellis (1803-1879) both in quantity and quality. It is believed the Philadelphia Mint replaced iron cast patterns with copper ELECTROFORMED patterns (GALVANOS) from Ellis’ models.
Rise of electroformed patterns.
Using iron patterns proved unsatisfactory, not only for the stylus drag, but also for the lack of finite detail. Models cast in iron could not reproduce the fine detail in the sculptor’s models. Reason for this was the meniscus formed at the juncture of all angular corners and, on coin and medal models in particular, where relief meets the field (called corner radius). This rounding of angles and corners occurs in all metal casting. It cannot reproduce sharp detail, notably the pointed junctures at the edges of relief and corner radii.
Fortunately an event occurred in 1837 to affect this. A German physicist and engineer, Moritz Herman Jacobi (1801-1874), developed an electro chemicalprocess he called “galvanoplasty” which today is known as electrolysis. This is the process by which electroplating takes place. But it can also be employed for forming objects from a mantel, core or pattern.
The technology was rapidly employed in England, for the silverware industry, but in France it was employed in the art field. Before long it was in use at the Paris Mint for making patterns for use on the die-engraving pantograph from sculptors’ models. Here it was ideal because all the detail in the sculptors’ models were reproduced in a copper pattern in far greater fidelity (in micron width!).
The metal pattern was called a galvano (from Jacobi’s “electrogalvanic” process). If the newly created pattern was positive to cut a die, it was also called a dieshell, if it was negative to cut a hub, it was a hubshell. (Electroforming changes polarity.)
This technology was in use for cutting dies on the die-engraving panotograph for the remainder of the 19th century and all the 20th century. It was replaced, only partially at first, by the use of epoxy for creating coin and medal patterns following World War II when it was developed.
Engraver’s use of engraving machines.
Because sculptors were asked to furnish relief models of portraits, more than any other subject to be made into patterns for dies, the first die-engraving pantographs were called portrait lathes.The engraver would make a hard surface cast of the sculptor’s portrait model and place this on the reducing machine.
In all instances these early engravers would utilize the sculptor’s bas-relief pattern to cut a positive image in steel. This reduction punch would then be hubbed into the master die. Lettering, subsidiary devices and rim elements would be added afterwards by punches and hand engraving.
In America, use of the die-engraving pantograph continued for 80 years to make reduction punches. This technique continued through the 19th century. It wasn’t until the invention of the Janvier pantograph that the entire die could be reduced and cut from the sculptor’s model of the entire design, lettering and all.
Tracer controlled pantographs.
In the last decade of the 19th century engravers and machinists devised pantographs to aid diesinking. One type of these was a tracer controlled pantograph where an oversize template model and template letters controlled a router that removed all the dead metal. It could carve out letters and leave the design as a flat undisturbed surface that required further diecutting.
The pantograph operator would have to manually control the router to mill away not only the background cutaway but also the surface metal to create the design. In effect this made this craftsman controlling this machine by hand as the engraver of the die. While this was quite satisfactory for letters, logos, architectural and other flat designs, it was left to the skill of the operator to create portraits, scenes and designs of highly modulated relief. Gorton was the major manufacturer of this style of pantograph.
Modern improvements of this machine, even computer control, have made this a quick and low-cost method of die engraving. Ideal for most dies, medal manufacturers use this in contrast to sculptured models. However, it produces less artistic, somewhat flat, mechanical images, particularly of portraits.
The computer will not design a coin or medal, but, like a burin in the hand of the engraver, it will aid the engraver to enter the design and determine the amount of depth each point should cut into the die or matrix.
Mints and medalmakers around the world were eager to accept the new technology, the most recent step in replacing the tedious act of hand engraving dies. The success of computer engraving may yet be proved to be limited, much like the use of the tracer-controlled pantograph introduced a century earlier. Both technologies have their place and will continue to be employed by the minting industry. They will not, however, replace the artist who must create the design nor the sculptor-medallist who creates more advanced designs.
The advantages of computer engraving is not only “fast and cheap” but also its versatility to alter a design, to modify it, to test a new concept, to hone the relief to a satisfactory image. As such it is ideal for simple images, as graphic designs, most trademarks and buildings. Where it falls short are very complex or highly detailed designs, but most notably, portraits!
One word describes what a sculptor working in clay or wax can accomplish that a computer cannot: vivify. In art it means “give life to.” A sculptor can give life to a portrait, make an image of a real person, so it seems the person is staring back at the viewer. He is alive in sight of the relief. In contrast, computer generated portraits are stiff, frozen and lifeless.
The computer engraver can start with a flat drawing, a cartoon, or create this on the screen. At each point on the design, called a pixol, X and Y coordinates are determined by the computer. The operator chooses the depth at this point, the Z coordinate, to fix the sculptural or dimensional effect, creating a bitmap. All these coordinates are stored in the software. A visual image is shown on the screen of the CPR. The operator moves through the design indicating the modulated relief.
When finished, the accepted digital design will then be transferred to a milling machine which does the cutting as controlled by the digital file. Afterwards, burrs and rough corners from the milling tool must be worked as with any other touchup of dies.
Is it possible to look at a coin or medal and tell how it was made, by hand engraving, die-engraved reduction, or by computer design?
Diagnostics: How A Coin or Medal Was Made
No hard and fast rules differentiate a hand engraved die from one made from sculptor’s models and dies cut on the die-engraving pantograph or by computer design by looking at any coin or medal. The difference, if any, is quite subtle and often difficult to detect.
Technically the only difference is where the rise of relief meets the background or field (called corner radius). and, perhaps, the crevices. Because of the rounded point of the stylus and cutting point on the pantograph and computer milling machine, which cannot enter these areas, these appear less distinct, less angular and more rounded. Also sculptors tend to fill up the model with detail more so than hand engravers, and occasionally vignette the surface (detail covers more of the model with less clean field) or with texture in the field.
- Generally, a hand engraved die will appear with sharper detail, steeper rise of relief, deeper crevices and a greater background area (smooth field).
- Generally, a die cut on a die-engraving reducing pantograph will appear with smoother, softer detail, slightly more sloping sides of relief, and less field area.
- Generally, a die cut on milling machine from a computer design will appear similar to that of a pantograph, depending upon the shape of the cutting tool.