This Appendix consists of
Engraving "tips" which should assist you when you are ready to actually engrave
the photographs that you have processed in PhotoGrav. The tips are provided for
a variety of the most common engraving materials that are suitable for engraving
photographs. The tips are primarily "finishing tips" that should enhance the
appearance of the engraved photos.
A1.1 Engraving Tips
Increasing the contrast on Cherry (or Maple) wood plaques.
After engraving, the use of liquid shoe polish will darken the engraved areas thus increasing the contrast. Care must be taken to prevent dye from bleeding under the plaque surface into the pores of the wood, permanently damaging the plaque. You will need the following supplies:
Brown & Neutral Kiwi brand liquid shoe polish with foam applicator top paper towels leather chamois water
Follow these steps for best results (first you seal it, then you dye it):
a. The cherry plaque should have a lacquered finish; it should NOT be raw wood. b. Laser engrave the plaque dry and unmasked. c. Wet the chamois and fold it to result in a pad that is several layers thick and about 4"x4" in size. Wring out the chamois so it is well soaked but not dripping. d. Smooth out the chamois so it is a nice flat pad. e. Seal the engraving by using the NEUTRAL polish. Using the foam applicator, liberally dab the polish on the engraving and brush around to cover all engraved areas. f. Immediately wipe off the excess polish with a clean pad of paper towel, quickly
followed by the wet chamois. Wipe lightly and briskly to clean the surface without pulling lots of dye from the engraved recesses. You may need to re-fold your chamois pad several times to maintain a clean wiping surface.
g. Let the neutral dye dry for 10 min. to seal the wood pores. h. Repeat the same procedure with the BROWN dye to darken the photo.
Shoe dye dries quickly and it is difficult or impossible to remove stains if you go too slowly and let it dry unevenly. Rubbing alcohol will clean some stains, but use sparingly as it can attack some wood finishes.
Walnut is a traditional wood in the industry but it surely does not work well for photo laser engraving since it tends to be quite dark and therefore results in very little contrast. If your customer insists on using walnut for a photo engraving, first try to convince him/her to let you put the photo on a separate plate like black brass or, better yet, the new Spectrum Lights ultra thin engraving material - it works fantastically well for photo engraving. If you do need to laser the photo into walnut, then use PhotoGrav settings for walnut that result in higher contrast and very little, or no, dot-dither shading so the processed image looks similar to a line drawing . Then, after engraving, use the dye procedure described in tip #1 above to attempt to get more contrast. However, use BLACK dye instead of the brown. Also, it is not necessary to seal the engraving first (with the neutral polish) because the walnut wood grain is tighter than cherry or maple so the polish won't bleed into the grain.
Don't even waste your time trying it. Oak is very porous and has an uneven grain hardness. These characteristics result in a very inconsistent and uneven engraving. Also, if you try to increase contrast using the dye technique of tip #1, then the dye bleeds like crazy under the plaque surface. Oak is light colored but the laser engraving is light also so your photo will not show up well at all.
Engraving on the back of the plaque, with the photo flipped left-to-right, always looks better than engraving on the face of the plaque. (PhotoGrav automatically processes photos for "back" engraving on acrylics unless you override the default).
Cast type acrylics produce a nice white frosty cut, but extruded acrylics (usually 1/4" and thinner) result in engravings that are mostly clear which is usually not very good for photos.
To engrave an acrylic plaque, use very low power settings - just enough to frost the surface on clear acrylic or remove the paint on painted acrylic (PhotoGrav automatically sets an appropriate power value when acrylic is the selected material). Engrave the plaque after removing the paper mask and let it dry. After it is dry, gently wipe any white dusty residue off with a clean, dry cloth. Then polish with a different clean, dry cloth using Novus #1 plastic polish. Spray the polish sparingly on the product and clean with the cloth. Use a dry spot on the cloth to buff dry.
Vector cut shapes or silhouettes from clear 1/8" acrylic and then engrave portraits, or other photographs, on the cutouts..
Laser engrave the photo, wipe it clean, and color it with permanent markers or spray paint. Let the paint dry and then sand off the back, leaving a frosted looking background with a color filled photo. (Note: With this technique, you would PhotoGrav-process the image in positive polarity, not negative. PhotoGrav's default polarity for acrylic is negative so you must override this default)
Spray paint the back of an extruded acrylic plaque before engraving. (We recommend Krylon brand spray paint.) Laser engrave the photo through the paint. Since it is extruded acrylic the engraving should be fairly transparent, so paint it again with another color, or back up with a shiny piece of gold, silver, or colored metal to show through the photo.
If , after engraving, the engraved areas are not very white looking, you might be using too much power, not too little. Try a lower laser power setting. Aluminum tends to have a narrow power response band for which the material turns nice and white. Too much power turns the aluminum a light yellowish color. Too little power does not remove all of the black anodized coating.
No clean up is normally needed but window cleaner works well if any is needed.
Engraving photos on Corian brand solid surfacing materials.
This material engraves nicely and is easy to color fill.
a. Engrave your photo. b. Scrub out the engraving with hot soapy water and a toothbrush. Rinse thoroughly and blow out with compressed air. c. Let dry. d. Dab enamel paint into the engraved areas. e. Using a piece of card stock, squeegee the excess paint off. This action also forces paint into the little dots in the photo. f. Let the paint dry. g. Wet sand with a block using 220 grit wet-dry sandpaper to remove the rest of the paint from the face of the plaque. h. Buff with a very fine scotch brite pad. i. Rinse the plaque off and let it dry. j. Polish the plaque with automotive wax or a good counter top polish like Hope's brand polish.
This type of plaque holds up well outdoors. It provides a great alternative to cast bronze and works well with photos also!
Alternative, indoor use only:
a. Use solid white Corian and engrave a photo or clip art. b. Use Permanent Markers to color the engraving in a rainbow of colors. c. After the plaque is dry, it can be sanded. An easier method, however, is to wipe the surface with a block wrapped in a paper towel that has been dampened with rubbing alcohol.
This is a newer material, with a satin brass appearance, that works exceptionally well with PhotoGrav processed images. It is very thin, about .004", and comes with adhesive already on the back. Engrave the material dry and unmasked at very low power. (PhotoGrav defaults to a very low power setting for this material). No clean up is needed after engraving.
Then, using your laser vector cutting capability, cut out the picture as an oval frame or some other interesting shape. Then you just peel off the backing and stick it on your plaque or anywhere. Great stuff!
Only use brass that is specifically made for laser engraving. This brass is shiny under the coating unlike the traditional black brass that is dull gold under the surface. Engrave the material dry and unmasked at just enough power to cleanly remove the coating and expose the brass. A larger power setting will wash out the detail in your image because brass does not absorb CO2 laser energy and therefore the excess energy is simply "spread" out, blowing away the details. It is best to not polish the engraved plate very much. However, you might want to shine the plate up using a little Pledge furniture polish on a soft, clean cloth. Most paper towels can scratch brass plates, so it is best not to use them. If you do use paper towels, the only ones to use are Bounty brand towels since they tend to scratch less.
This "frosted" effect is caused by the laser not fully penetrating the clear finish on a plaque, especially in areas where there are few dithering dots. This effect can be reduced with a product know as "Almond Stick" which can be ordered from the Fuller Brush Company or can be found in some woodworking supply catalogs, furniture stores, or hardware stores. After engraving, you simply dab some of this product on the plaque surface and buff off with the palm of your hand. Most of the "white stuff" is subsequently hidden. Almond stick also hides small nicks and dings on wood plaques.
Most light colored plaques of this type are okay for engraving photos. After engraving, the "Black dye" procedure described in tip #1 works quite well.
The melamine type laminated plaques like PDU brand Spectra-Lights work exceptionally well for photo engraving. They accept dye and color fill readily and their surface is much more durable than most. Quail brand melamine plaques also work quite well.
One note of caution: Some of the cheaper plaques of this type may swell up around the engraved areas after you get them wet using the "Black dye" method. It is always wise to test your own suppliers' plaques before you commit to any job.