The Etching Process

Rembrandt, Picasso, Goya, and other masters, used etching to express their artistic vision. This historical art form is used by printmakers today. The etcher uses not only her artistic talent, but also must balance the delicate chemistry involved in developing the image on the plate.

The traditional etching method is unique in that it allows the artist to produce a limited number of almost identical images. Sculptors have a similar process, using one mold and casting it multiple times. Etchings are not simply reproductions, however, as the artist is involved in every step of the printmaking process: drawing, etching the plate, pulling each print, hand-coloring the etching, and finally numbering the edition. Thus, each etching is an original work of art.

The etching process begins in the artist’s imagination, expressed as a drawing. The artist then uses a copper or zinc plate, coated with an acid resistant wax. Her drawing is scratched on the surface of the plate, cutting through the wax, and exposing the metal beneath.

This plate is then immersed into an acid bath. The wax protects most of the plate from the effects of the acid. However, the acid bites away at the bare metal, ‘etching’ or producing grooves in, the surface of the plate. Variations in shading are determined by the length of time that portion of the plate remains in the acid bath. For a single line, the deeper the line the more ink it will hold, and, the darker it will print.

When the acid process is complete, the wax is removed and the plate coated, by hand, with an etching ink. The ink is carefully wiped off the plate surface, leaving the bitten lines full of ink. This wiping determines the appearance of the background of the finished etching. The inking process is repeated for each print in the edition.

Next, a dampened piece of acid-free paper is placed over the etched and inked plate. The plate and paper are then run, by hand, through a flatbed press under very heavy pressure. This process forces the paper into the recesses of the plate, picking up the ink, resulting in a reversed, but exact reproduction of the plate. This reproduction is called an intaglio etching.

Some etchings are composed of only this inked print. Some artists use multiple plates to produce colored etchings. Other etchings are finished with a variety of media. Once the etching is dry, the artist can embellish the etching using watercolors, pastels, etc.

One of the factors that make etchings more valuable is the fact that the plate will wear down with use. Therefore, hand-pulled etchings are limited to a certain number of impressions for each edition. This maintains the highest intaglio print quality, as well as giving the artwork enduring value.

Each etching is then signed and numbered by the artist. This numbering tells the art owner both, the total number of etchings in the edition, and, the number of this particular etching in that edition. For example, an etching might read 24/70, meaning that this is the 24th impression in the edition of 70. Many artists designate a small portion of the edition to Artist Proofs, or AP’s. Artist Proofs are the impressions used to ensure the quality of the numbered pieces.

Today's fine art printmaker can choose from several methods to produce an etching plate. Many artists are now using an alternative method to create an etching plate without the use of acids and toxic chemicals. The process of solar etching has evolved using an aluminum plate covered with a layer of photo emulsion. The plate is created by placing a transparency made from the original drawing over the UV sensitive surface, exposing it to the sun, and then developing it in water. Once the plate is created, the steps of inking, wiping, hand-pulling and hand-coloring the etching is the same as in the traditional method described above.

Etching is a unique art form providing the collector with a beautiful, original work of art.

© 2006 Melanie Fain - All Rights Reserved Worldwide.

Melanie Fain is an artist and naturalist, famous for her beautiful watercolors and hand-pulled etchings. Melanie loves to bring the natural world to her collectors and specializes in birds, insects, and botanicals. Melanie's art has been exhibited throughout the United States in select exhibitions and art shows. Visit Melanie Fain's website to view and purchase her etchings and watrcolors: http://MelanieFain.com/

Laser Marking and Laser Etching on Glass for Industrial Applications

The marking of glass for industrial use has been done for hundreds of years. In the past the methods used have included ink stamp marking, sand blasting, air grit, acid etching, scribing etc.

Industrial applications of glass marking include:

1. Marking of safety information on safety glass used in commercial and residential construction. This includes glass areas around doors and/or entrance and exit locations.

2. Marking of glass for commercial and residential construction to identify the glass or door manufacturer [for product identification and marketing/sales activity]

3. Marking of headlamp or tail light lens in automotive applications for manufactures name, year of manufacture and/or part number. Also used in the manufacture of televisions for marking mirrors and lens.

4. Marking of serial number, product identification, or other manufacturing information for the prevention of theft and validation of warranty claims

5. Marking serial numbers, part numbers, text, or bar codes allowing for parts to be tracked though the production process until final assembly and shipment

The traditional methods of glass marking all involve contact with the surface of the glass product which exposes the product to stress and potential damage. Co2 lasers offer significant advantages for marking glass products. The RF excited sealed beam Co2 laser coupled with a galvo head and software offers the fastest, cleanest, most reliable method for marking and etching glass.

A Co2 laser can laser mark glass with bar codes, especially 2-D or data matrix bar codes, which can easily be coupled with vision systems for reading the data contained in the bar code. The use of bar codes on glass allows for the product to be tracked all the way through the production process until final assembly. This helps assure a continuous uninterrupted supply of product. The laser marked or laser etched bar code can also be used after the sale of the product for identification purposes and validation. This helps to eliminate warranty costs related to counterfeit or unauthorized products.

A Co2 laser marked or laser etched bar code can also be read by vision systems in the manufacturing process to determine the identity of the part. Examples include prescription strength of eye glass lens, or the type of front headlamp lens used in a Honda Civic. This ensures that the part is sorted and used properly throughout the manufacturing process and that the correct number of parts is produced based on anticipated sales for final assembled components.

The advances of Co2 laser marking of glass over traditional methods are extensive. These include:

• No contact with the part as in scribing methods thereby reducing the possibility of breakage to and damage of the part, as well as elimination of the maintenance required for the scribe unit

• No solvents, thinning, or cleaning agents to purchase and keep in stock as in the case of ink marking or ink printing systems, thereby significantly reducing costs of operation and eliminating the need for continuous maintenance associated with these various ink printing technologies

• No pads for ink printing to maintain as they can fall to an angle or become turned sideways causing the printed image on the glass to appear sideways or not square

• No need to stop the glass in place and make sure a secure fit with the rubber mask is formed as in the case of Airgrit marking

• With Co2 laser marking for industrial glass applications the product can be marked on the fly [while moving]. If stopped or 'squared' for marking, five to eight lines of text plus logo's can be laser etched in less than 0.5 of a second

• With Co2 laser marking no supplies are necessary and no secondary process exists for cleaning or maintenance

• With Co2 laser marking changes to the mark [different text, different logo, difference shape, etc] can be accomplished with a simple click and drag command of the mouse

Co2 laser marking for glass in industrial applications is the fastest, most effective, least costly method in which to mark the product.

Jim Morin writes for Worldwide Laser Service Corporation a company that specializes in T.E.A. Co2 lasers. For more information visit http://www.wlsc.com

Understanding Laser Marking and Laser Etching Systems

Laser marking and laser etching are becoming more and more important in a growing number of industries. The basic reasons to laser marking or laser etch your products include:

• The mark is extremely durable, permanent and in most cases cannot be removed without destroying the product itself, this is true for laser marking, laser etching, or laser annealing.

• The laser marking process is accurate, 100% repeatable, fast, with very clear sharp results.

• The laser mark or laser etch can quickly and easily be changed without any machine change over, and, without replacing any tools. The changing of a laser marking or laser etch is a simple drag and click computer operation.

• The laser requires no consumables and no additional purchases of added materials or supplies. Therefore the operating and maintenance costs of owning and running the laser marking or laser etching system are virtually non existent.

Laser Basics

The word laser is an acronym for light amplification by simulated emission of radiation. The laser beam is formed in a sealed tube with an electrode set, laser gas, and electrical discharge. The beam is emitted into a telescope which expands the laser beam from a size of approximately 2mm as the beam exits the laser tube up to 7mm to 14 mm for most laser marking or laser etching operations. The expanded beam is directed into a laser head containing two mirrors located on high speed galvo motors. The laser beam is directed off the mirrors though a single element flat field lens to the product being laser marked or etched.

Typically the laser marking or laser etching fields created range in size from 65mm x 65mm [2.5” x 2.5”] at the smallest size to 356mm x 356mm [14.0” x14.0”] square at the largest. The next consideration is the laser beam spot size. This is the size of the focused laser light energy at the laser marking or laser etching point on the product and can vary from approximately 200 micron [micrometers] or .0078” at the smallest to approximately 540 microns or .021” for Co2 lasers. The laser beam spot size ranges from approximately 20 microns or .0007” at the smallest to approximately 70 microns or .0027” at the largest for Nd:YAG lasers. These small spot sizes and highly focused laser light energy create the detailed, clear, permanent marking that is typical of the laser marking or laser etching process.

Controlling Lasers and Laser Marking Options

Laser markers and laser etchers are controlled via software. Several variables need to be controlled:

1. Laser power as measured in watts

2. Frequency, meaning the pulse frequency of the laser beam

3. Inches per second, meaning the speed that the beam steering mirrors are moving

Determining the correct setting for the laser is the single most important and critical element in the success or failure of the laser marking process. Once the proper settings have been determined and demonstrated a 100% repeatable laser mark can be achieved.

Laser controller software is accessed via a PCI interface card. This sends the digital signals of the computer based marking or etching files to the motors and directs the laser beam to the product being laser marked or laser etched.

There are several different types of laser marking and laser etching and several different considerations in terms of visual results for the laser mark or laser etch.

1. Laser etching produces a visible etching or depression into the material. Laser etching replaces traditional process like mechanical press or pin scribing. Laser etching can be done with either a Co2 or YAG laser on virtually any material surface and to any depth from very light etching to very deep etching. For example, laser etching is used to engrave serial numbers into metal gun frames. Generally speaking with laser etching the material being laser etched is vaporized at the laser etching point due to the typically high power densities of the laser beam at the point of laser etching.

2. Laser marking produces a surface mark with very little engraving and very little disruption of the material surface. This is especially useful in certain industries such as discrete electric components, semi-conductor, electrical fuse, and ceramics where laser etching can actually damage part or change the conductive qualities of the part. Generally in order to produce the laser mark without deep engraving a high speed per inch setting for the galvo head is used.

3. Laser etching and laser marking generally do not produce any color changes and create a colorless impression. There are exceptions as certain plastics will sometimes react to and change color under either Co2 or YAG laser light. Also, in some cases, additives can be incorporate into the materials being laser marked or laser etched in order to produce a color change. Another exception occurs when the wavelength of either the Co2 or YAG laser is changed from those typically used in laser etching and laser marking. This can produce a color change after laser etching on some materials.

4. Laser annealing is another popular form of laser marking. This type of laser marking is generally undertaken with a YAG laser on metal surfaces using lower power, high frequency and slow writing speeds to produce heat on the surface of the product. Laser annealing can be used to replace electro chemical etching and ink marking as the laser annealing process creates a black mark with no etching. Care must be used, as the heat generated can cause iron in some metals to be pulled to the surface, and rust can result if the parts are subjected to sterilization after laser annealing. This can be an especially difficult issue for medical devices

5. Laser ablation is also a popular use for laser marking systems. In this case the laser is used to remove a layer of paint, anodized or some other material covering the surface of the part. For example this process is used to create bear metal contact points on a painted part, to allow battery connection as in cell phones, or to remove paint for identification of parts and manufacturer details.

Jim Morin writes for Worldwide Laser a company that specializes in Co2 and YAG marking systems used in a wide range of applications. For more information visit http://www.wlsc.com