The painted plywood method uses one base color and one top color. The concept is to burn the top color just enough to reveal the base color, but not enough to burn through the base color.
- Cover the entire plywood sheet with a very fine layer of dry wall compound. Scrape as much as possible, such that only the cracks are being filled.
- Sand the plywood sheet using a hand belt sander. Try to get the sheet as smooth and uniform as possible.
- Choose a base color. This is the color you will be revealing when engraving. For instance, if you would like to print a black logo on a white background, your base color would be black.
- Any paint can be used. I personally use basic Latex water paint. For the base layer, you can brush it on the wood or spray it. If spraying, ensure it is tick enough so the laser doesn’t easily burn through it.
- Apply a minimum of two coats, with a quick sanding between the coats. The objective is to have a smooth finish.
EDITED 25 Nov 2019: It is extremely difficult to use a dark base color, as a light color will not cover it well. For instance airbrushing a white paint over a black base required a high number of layers to lighten it. First few layers had no impact whatsoever (this might be due to the quality of the top layer paint, and how thinned it is).
- Cut the sheet of plywood to appropriate size. Good size is 4×4 inches for small photo engraving, and 12×18 inches for bigger signs. Keep in mind that a photo will take approximately 1hr for a 4×4. The bigger sizes should be used with vector drawings only.
- Cutting on the saw should be done with painting facing downward to prevent painted face from chipping.
- Using a router table, create an edge to each tile.
- Sand the bottom and side of each tile using a belt sander until smooth.
- Choose a top color. This top color will consist of the background color of your engraving.
- Water based paint is the best for this stage, and makes cleaning easier. At this stage, it needs to be sprayed in order to have a very thin and uniform layer. It can be either from a spray paint canister, or airbrushed.
- If using an airbrush, thin the paint with water or adequate solvant until it has a milky consistent. See my post on airbrush thinner.
- Ensure you paint the sides as well.
- Image prep can be done in any image processing software (GIMP, Paintshop Pro, Photoshop), or can be used within Lightburn directly.
- The goal is to have increase the sharpness (unsharped mask) and adjust the brightness. Although it might not look good on the computer, it will have a different result once engraved.
- The dithering can be either done in the image processing software, or within lightburn. If done ahead of time, ensure the image is resized to the appropriate dimension and dpi. Then in lightburn, you will need not to resize the image, and engrave using the “passthrough” option. Jarvis dithering seems to give best results.
- Before engraving, look at the preview, and ensure the black area is burned completely and the white is not.
- Ensure laser is cleaned and focus appropriately.
- Use “frame” option to ensure the engraving area is adequate and centered.
- For a photo image, engrave at 1500 mm / min, 25% power, 254 dpi, Jarvis dithered.
- For a vector image, engrave at 1500 mm/ min, 25% power, 127 dpi, fill shapes individually and flood fill. Due to the high speed, do not use “line” to trace the contour, as the entry and exit point will result in overburnt in these area.