Awards & Engraving

October '18

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22 • A&E OCTOBER 2018 a photograph, grayscale image, or other graphic where relative colors are important is engraved without inverting the image in the drawing, a negative image will be the result. To get a positive image, you must use a negative image. The exception is when the color of the tumbler is lighter than the exposed metal, as in some of the can coolers in the photo above left. You can see that the engravings appear dark on the light-col- ored coolers and light on the dark-colored coolers. It comes down to judgment when deciding what to do with these exceptions. While white text and other design ele- ments are perfectly acceptable, I can say without exception that any grayscale or photographic image must be inverted to make a positive image on glass and clear cast acrylic. Unless it will be color-filled, laser engraved marks on glass and clear acrylic are always white. Even though the material is clear, glass and clear acrylic can be considered dark materials. Put an engraved glass in front of a white back- ground and the engraving will disappear. It has to be seen against a dark background. Also remember that if engraving on the reverse side of glass or clear acrylic, the entire drawing needs to be mirrored. That way it will look normal when viewed from the front through the material. Glass seems to be the medium where most of the nega- tive image mistakes are made. Sadly, I've seen negative images on projects as large as church door windows. Slate, black granite, and black marble fall into the same category as glass and clear acrylic. They all engrave with a whitish mark, so inverting the graphics in the drawing is required to get a positive image. On most colored, opaque cast acrylic, the mark made by the laser is lighter than the original color, so an inverted image is usually required. If, however, the raster is to be filled with a color darker than the original color, the graphics in the drawing do not need to be inverted. What is done with graphics on wood depends on the final finish and the desired outcome. Always determine whether the final engraving will be darker or lighter than the final finish of the wood. Dark burn marks on lighter wood means a positive graphic is needed. Lighter marks, whether lighter than a stained wood or color-filled to be lighter than the wood, require a nega- tive or inverted image. There are a few ways to make marks on fabrics. The two most common methods are burning and fading the color. Burning is usually done on lighter colored material. While not recommended if the integrity of the material is to be preserved, it is accept- able for display pieces. In this case, a mark is made that is darker than the material being marked, so the graphics in the drawing do not need to be inverted. A positive image should be used. Fading the color on material is usually done with a low power, high speed raster on dark material, like blue jeans or cotton duck canvas. A lighter mark is being made, so the graphics — at least any grayscale or photographic images — in the drawing should be inverted. "Darker mark, let it be. Lighter mark, inversion is key." SUBJECT OF INVERSION I positively tried my best not to be too negative about the subject of inversion. It's not as clear-cut of an issue as first might be assumed. You may have to invert an entire graphic or just a part of a graphic. Adding backgrounds and borders may also be necessary. It takes some judgment and trial and error to get the best results. It will eventually become second nature when it comes to knowing what to do. There will still be mistakes but just own up to them and make the corrections. Be positive by going negative — invert! Laser Engraving Left: a clear bell — inverted and mirrored; no fill. Center: ivory ornament — not inverted; color-filled with black. Right: a black bell — only the church is inverted; color-filled with white. When working with color-coated tumblers, to get a positive image, you must use a negative image. The exception is when the color of a tumbler is lighter than the exposed metal, as in some of these can coolers. A&E

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