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Technology Focus

Making That Engraving Choice

by Jeff Peterson

February-March, 1999
The question is constantly asked throughout the foil stamping and embossing industry on a daily basis. What is the best type of engraving metal to use? The answer is definitely not cut and dry, and many factors must be considered. We have summoned the advice and recommendations of several experts in the field to help analyze the different metals and provide guidelines for choosing each.

Brass

Brass is the most versatile of all engraving metals. It is also extremely durable and is generally used when the highest quality die is required. It is most commonly used for hand tooled and machined embossing engravings (Multi-level or sculptured), but is also useful for long-run flat stamping jobs. Because it is easily tooled, it is an ideal metal choice when an image needs to be "opened" up so that the foil stamps clean without the image filling in.

Brass engravings are the industry standard for combination (foil and embossing) dies as well. When an image can be foil stamped and embossed in one pass, brass is the best choice because it can be easily machined to create the needed relief to apply foil and emboss the image simultaneously. Brass is more expensive than copper and magnesium, so you must analyze your application carefully before choosing it.

Copper

Copper is a common metal for flat stamping and single level embossing dies. It is an extremely hard metal with good etching attributes, which makes it an excellent choice for medium to long foil stamping runs. If run length exceeds somewhere between 20,000 to 30,000 impressions (depending on other factors such as image size and stock), than you should consider choosing copper for a flat stamping or single-level embossing application. You may also want to consider ordering a copper engraving if you know the job you are stamping will run again in the future. This will help eliminate the need to re-order dies each time you run the job. In addition, copper engravings are an excellent heat conductor and maintain their heat very well. This is especially important when foil stamping on high speed equipment where the speed and action of the press is more likely to cool the die temperature.

The surface area and design of your foil stamped image can also help you determine if copper is the best choice. A medium to large solid area of foil requires much more tonnage and pressure than smaller images or type. A copper die is recommended for these types of applications to ensure the die does not begin to crash under the pressure of the stamping press. In addition, very fine detail images may require a copper engraving because of the crisp edges that an etched copper die has. Lastly, if you are using a textured or recycled stock for a foil stamped image, copper is most likely the metal to use. Again, because of the extreme hardness of copper, a copper engraving is less likely to become crashed or worn than softer metals when foil stamping textured or recycled stocks.

Copper is usually priced slightly higher than magnesium, but is less expensive than brass or steel engravings. Copper takes somewhat longer to etch than magnesium, although turnaround times are still relatively quick.

Magnesium

Magnesium dies are a fast, cost-effective, versatile choice for foil stamping and some embossing applications. They are ideal for short runs (somewhere between 10,000 and 40,000 impressions), depending on the size of the image and type of stock.

If the surface area of the foil stamped image is relatively small to medium in size, magnesium will yield excellent results. In addition. fine detail and unevenly distributed artwork designs require relatively less pressure and can be readily achieved with magnesium. The paper stock should also be smooth or coated when foil stamping with magnesium. As stated earlier, recycled or textured stocks can cause problems and could cause a magnesium die to become damaged during the press run.

Magnesium is also used by some engravers to produce sculptured embossing engravings because of the softness of the metal. When used for this purpose, it is recommended that duplicates be made for use in a production run. The magnesium die becomes the master that can be used to make more duplicates in the future (duplicates will be discussed later in this article). This is an option for large applications where a sculptured image is being run several up on a sheet. If the job requires a one-up sculptured embossing die, brass is the best choice because of its strength.

If cost is a factor, magnesium is generally the least expensive metal. In addition, magnesium dies are the fastest to produce. The "etch rate" of a magnesium plate is approximately .007" per minute, so a photographic image can be chemically etched to .100" depth in less than 15 minutes. This rapid, deep etch capability eliminates the need for hand or machine routing of background open areas. Because of this, magnesium dies are usually available for same-day or one-day turnarounds

Steel

Steel engravings for foil stamping and embossing applications are not widely used in the industry, but are recommended for some applications. Steel is primarily used for flat stamping jobs requiring extremely long runs (usually over one million impressions) on thick paperboard material. A foil stamped carton for a consumer product such as a cereal box or toothpaste carton is a circumstance where a steel die might be used, especially if the job will most likely run over and over again. Steel dies are also a good choice for thick, hard-to-stamp materials such as leather and vinyl.

Steel is very difficult to machine and is the most expensive type of engraving to manufacture. Unless you are involved with a very long run on difficult stock, you would most likely not choose steel as your engraving option.

Duplicates

Duplicates are manufactured by many engravers for use on multiple-up embossing jobs. An original embossing engraving is created from brass or magnesium and then duplicates are molded from the original which are exact copies in depth and detail. The material used for duplicates is usually made of a fiberglass-like material or a hard plastic called Bakelite. This is the most cost effective way to emboss multi-level or sculptured images that are more than one-up on a sheet.

If you are using duplicate engravings, it is recommended that you use all duplicates on the job, especially if you are embossing with heat. Do not use the original engraving at the same time with duplicates because the heat transmission of the original embossing engraving is much different than the duplicate. This will help assure that you do not scorch or burn the embossed image during the run.

The number of impressions that you can expect to achieve with different types of engravings is difficult to judge. We have provided estimates in this article, but there are many factors which will determine how long a die will last:

  • Type of stock (smooth or textured)
  • Thickness of stock
  • Amount of tonnage used on your press
  • The press operator's care when handling dies
  • The press operator's makeready technique
  • How many "up" the job is running
As you can see, there are many factors involved when choosing the right type of engraving. Hopefully, this will help you with your choice, but the best advice is to establish a good relationship with your engraver and trust his or her judgment based on the type of job you are running. Of course, like everything else with foil stamping and embossing, there is some trial and error on what will work for a specific job. Everyone has their own comfort levels with what works best for them. As a foil stamper once told me, "It's a jungle out there, and we're right smack in the middle of it"'

InsideFinishing would like to thank Ben Greenspan of Greenspan & Kushlin (800‑2EMBOSS), David Juillerat of Spectrulite Consortium Inc. (800-851-3145), Rudy Henn of Owosso Graphic Arts, Inc. (800-444-5552), Tina Schad of Clodfelter Engraving, Inc. (314-968-8418), and Joe McDonald of Adolph Bauer Inc. (781-767-4350) for their assistance with this article.