Laser Engraving Stone Products

Copyright © 2003 by Davis Multimedia, Intl. All Rights Reserved.
As Printed in April 2003, Volume 28, No. 10 of The Engravers Journal.
 

    Some things really are meant to be engraved in stone, just as the old saying goes. Offering laser engraved stone products to your customers opens a wide range of markets such as memorials, desk accessories or decorative tiles. What makes this form of personalization have such a high perceived value to a customer? On the top of the list is the permanence of the engraving. Dating back to ancient times, important documents were engraved into stone tablets for posterity. The longevity of the engraving was considered crucial in days of old, and is still thought of in the same way today.
    Customers also view stone items as timeless and make purchases due to the solid feel and weight of the material. Stone is heavy and has a feeling of quality, elegance and durability — and these features mean value. In our society of plastic “throw-away” products, the durability of an engraved piece of stone has worth and appeal for many years to come.
Stone Varieties
    Stone materials that are suitable for laser engraving vary in quality, color and texture. Many produce brilliant results. Marble is a common stone variety that can produce highly detailed results. Marble generally has a very fine texture and is suitable for engraving photos or detailed text. The color range of marble is one of its benefits. Beautiful and rich colors like Jet Black, Green, Rose and White make marble popular with many customers. Hewn from quarries around the world, better engraving-quality marble comes from India and Pakistan where the marble trade has existed for hundreds of years.
    Slate is another type of natural material that can produce good laser engraving results. Slate is relatively soft and sometimes has a very uneven surface. It’s a fine-grained, metamorphic stone derived from sedimentary rock shale. It is uniform in color, and available in shades such as dark to light green, mottled purple, black, gray or dark red. Veined patterns from overseas have also recently been introduced. Unless its surface has been honed smooth, slate can be recognized by its distinct cleft pattern. Slate tiles are commonly available in several sizes and are frequently used on walls and floors.
    Granite is a stone variety that is dense-grained and possesses excellent hardness and durability. For this reason, it’s very popular for memorial and architectural applications. It is an igneous rock, which means it was once molten, and formed as it cooled deep within the earth. Minerals within granite typically appear as small flecks throughout the stone, creating a “salt and pepper” look. Other types have veining similar to marble.
    Granite can be highly polished or finished in a variety of ways. Comprised of feldspar and quartz, granite is available in a range of common colors including black and red, which are the most common for engraving applications. The consistency of granite can sometimes be rather coarse or crystalline and may best lend itself to engraving applications involving text and graphic designs.
    Travertine marble is a variety of limestone formed in pools by the slow precipitation of hot, mineral-rich spring water. The “holes” that are characteristic of travertine are created when carbon dioxide bubbles are trapped during the stone’s formation. Although classic travertine is recognizable by its homogenous ecru or dark colors, other shades such as dark reds with dark brown veining are available. Travertine is available in cut and polished standard tile sizes and is commonly used for flooring and countertops.


Laser engraving on stone materials usually provides a white cut. Figure 1: A laser engraved marble nameplate creates an elegant piece that customers love.

    Sandstone, as the name implies, is comprised of fine sand particles bound together by nature’s own concrete-like glue to form this uniform stone product. The color of the sandstone is created over the course of time by minerals being washed through hardened stone. Sandstone is somewhat brittle and has a coarse quality due to the embedded sand mixture. Laser engraving results can be very good as the stone can be very flat and is relatively soft in density.
    River rock is another stone type to consider for laser engraving. Engraved river rock has found its way into markets such as corporate gifts, gardening and even as pets for some folks. When referring to river rock, we’re talking about actual stones from river beds that have spent centuries becoming smooth, rounded and polished by flowing water. These sedimentary stones are comprised mostly of sand and will engrave with a medium to coarse quality. The more ideal types of river rock are those that are darker in color with a highly polished, flat surface. A sprayed-on clear coat can also help to create a smooth surface for laser engraving.
Shallow Engraving
    Several options are available for laser engraving on stone, and all can achieve very good to excellent results. While considering each of the processes to work with, keep in mind that the base material is stone. While not trying to overstate the obvious, stone varieties are natural materials and can vary greatly from one example to the next. These materials were created by heat and pressure over millions of years and no two pieces are the same. Our goal in this article is to educate you on the materials and processes so that you can make knowledgeable adjustments to achieve professional results.
    The best you can ask for with most stone products is to have a level of consistency from a supplier that reduces the variables slightly. Many suppliers can presort the finished goods into similar or like product groups to achieve a level of consistency in the products they ship you. Even with the presorting of finished products, color and size will vary and should be considered in the engraving process.
    The easiest process for laser engraving stone is to simply focus the laser beam on the top of the stone and engrave as you would on acrylic or wood. This style of direct engraving can best be described as a bleaching process where the laser energy whitens the stone during engraving. During laser engraving, the color embedded in the stone will be removed to reveal a white color. The laser engraving system will effectively remove the color of the stone that took millions of years to filter in. The depth of engraving from the laser will not be deep; in fact, it is often barely perceptible. That does not mean the engraving will look poor, though. Highly detailed photos and text can be laser engraved onto stone for truly professional looking results.
    One of the keys to achieving crisp, clear engraving quality is to find the correct power and speed settings for your laser system. Keep in mind that the recommended power settings in your laser system manual are just a basic starting point. Optimize your settings by test engraving on a similar sample of stone and examine the results. One common error is using too much power for engraving on stone. This results in engravings that look unclear or blurry. The laser can develop enough heat energy to start to crystallize the stone and fuse particles together. Conversely, using too little power will yield results that are gray instead of the desired white. Running the same job a second time may clear up the engraving quality to a whiter shade. However, adding more power in increments of 5% until the ideal setting is found is a more permanent solution.


Figure 2: Paint filling allows you to add practically any color to the cut. Figure 3: A sandblasting stencil is easily created by lasering through pressure-sensitive polyester.

    Direct laser engraving will create a white engraving color in contrast to the base color of the stone. The natural stone may have some white veins or streaks that run through it, causing some readability problems. Since the vein color is usually white and the engraving is white, the effect of engraving over the top of one of these veins will look like the engraving has a lightning bolt running through it as the vein blends into the engraving. Positioning the engraving so as to not interfere with the vein is the best solution in this case.
    Need to add some color to the engraving on the stone? Consider a color fill process that is made easy using the laser. When working with highly polished stone materials, the color fill process starts with the direct engraving of the stone. The direct engraving of the laser has broken the top, polished surface of the stone and left an engraved area that is now porous and will soak up the color fill material. Recommended color fill products are ones that are lacquer based, not acrylic based. The acrylic-based color will float on top and not soak into the stone like the lacquer-based materials. Typical colors for adding to laser engraved stone are gold, silver and copper. The ideal product would be an ink-like product.
    Using a small paint brush, dab the color on to the engraved area, allowing it to soak into the engraving. While the color is still wet, wipe the area with a soft, clean cloth. Any residual color can be wiped clean with a soft cloth and mineral spirits. The results of adding color can be outstanding. It can add the brilliance and clarity to engraved stone products that customers are willing to pay for.
    Note: This description of color filling is greatly oversimplified, and color filling is also useful for many other materials besides stone. For these reasons, I’ll be taking a more in-depth look at color filling in one of my upcoming articles.
Deep Engraving
    Creating deep engraved areas in stone can be accomplished using a laser system, polyester sandblast masking and a sandblasting system. Start by applying a laser-safe, polyester mask to the stone. Now you can use your laser to engrave through the mask and into the stone, creating a stencil or mask for sandblasting. After laser engraving the stone piece, you are ready to sandblast to the desired depth. Most of the stone types we have discussed in this article are relatively soft and can easily be sandblasted to a depth of 1/4" or more using a quality polyester mask.
    Ready to add color to your sandblasted product? After sandblasting, clean off the stone with some compressed air. It is now ready to be spray painted. Apply a smooth, even coat of high-quality spray paint to the clean area and let it dry. Be sure to leave the mask in place to make cleaning up after painting a breeze. Simply remove the mask and clean up any excess paint.


Figure 4: Lasering a photograph onto black marble is easily accomplished.

Engraving Photos on Stone
    Photo engraving is one of the fastest growing segments of the laser engraving industry. The ability to put a treasured photo onto stone using a laser is a proven process. Proven to generate more sales, that is!
    Like any digital process, laser engraving photos should start with a decent quality photo to scan. The process begins by scanning the photo at the dpi that you intend to engrave with. Typical engraving dpi settings are 500 or 600, depending on the laser system you have. Scan the photo as a grayscale bitmap format in the correct dpi resolution. Using Photoshop, a program developed specifically for lasering photos, or Corel’s PhotoPaint, scale the photo to the final engraving size using the “resample” tool. To add some professionalism to the engraving job, add a featheredged vignette or drop out the background behind the subject using some of the basic tools in the program.
    The image is now ready to import into PhotoGrav software for processing. PhotoGrav software offers many advantages for laser engraving photos on to all sorts of materials, including stone. PhotoGrav can compensate for marginal-quality photos by automatically creating a histogram, which it uses to compensate for contrast and density failures in the original photo.
    Another automatic feature of the software is called edge enhancement. This is particularly helpful with materials like stone when the subject has a tendency to blend into the background. The automatic edge enhancement feature provides a little more contrast around the edges to make the subject more pronounced.
    Using the PhotoGrav software is easy. It’s just a matter of opening the grayscale bitmap scanned image and selecting the material to engrave on. A dropdown menu lists dozens of commonly found engraving materials and each one has unique settings to make the engraving process more accurate. Select the “Black Marble” setting for engraving on stone products. Click the “AutoProcess” button and let PhotoGrav do its magic.
    When the process is complete, save the “Engraved Image” in a folder on your computer. I keep a folder on my desktop called Engraved Images to make the files easier to find. The Engraved Image is what will be imported into CorelDRAW or your current layout software and then printed to the laser, along with any text or other graphics that will be incorporated into your layout.
Multiple Markets for Stone
    Laser engraved stone products cross over into many different markets. Flooring is certainly one market. The ability to create custom floor designs is one that many distributors of floor products would like to know about. Gaining in popularity today are the so-called “donor floors” or “walks of fame,” used to recognize or commemorate people or organizations.
    Commercial and residential designers and builders also need to create custom products for their customers and could be a market for laser engraved stone. Memorials for people and pets continue to be a growing market and one that is neither price sensitive or subject to consumer market swings. Many corporate premiums and desk accessories are made from marble and fit the corporate customer need of looking “different” or “upscale” to impress customers.
    Of course, these are just a few marketing applications for engraving stone products. With your laser engraving machine, some stone and a little imagination, the sky is the limit!

 

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