3D Illusion Slate Coasters: Tips for Preparing, Processing, and Engraving

Back on slate for a change of pace. Slate coasters 3D illusion images. Sanded smooth / satin black acrylic prep. Engraved with OMG 60W MOPA fiber / 150mm lens.
— Engraved by Ritty Geary.

Image Preparation Tips

Always invert raster images (PNG or JPEG). Inverting is not necessary for text fill or line SVGs. Begin with a negative to engrave a positive image on any material that lightens as it engraves (slate, white tile painted black, alloy card/dog tags, etc).

Image processing is key: Sometimes a straight invert might work, but adding brightness, contrast, levels, shadows, and highlight adjustments can improve results. The laser engraves the darkest areas hardest and brightest, while ignoring white spaces.

For more detailed guidance on laser settings and optimization tips, check out our Laser Settings & Tips article.

Coatings and Surface Prep

Pre-coating is personal preference. I use satin black acrylic spray paint—it darkens the surface and allows the laser to create deeper grayscale shades, improving detail.

Sealing or clearcoating is optional; I usually skip it because it can dull the image. Properly engraved slate already has a permanent image as the laser changes the molecular structure of the stone.

Sanding smooth is optional. Raw surfaces are fine, but ultra-detail work benefits from a smooth prep. Failed attempts can be sanded down and reused.

DPI, Focus, and Engraving Parameters

• DPI: Slate doesn’t overburn like wood. Use your machine’s maximum DPI within your focal dot specs. For example, a 0.06mm x 0.08mm dot equals ~423 DPI.
• Focus: Focal cards are approximate; ramp tests determine optimal focal height. Different machines may vary slightly even with the same model.
• Engraving Parameters: Slate engraves easily with low power and moderate speed. Overpowering or moving too slowly can create a bumpy gold effect—aim for bright white to grey.

If you’re interested in exploring more fiber laser projects and tutorials, visit our Fiber Laser Projects section for inspiration.

Testing and Fine-Tuning

Perform small-scale test grids before full projects. Parameters from other users with the same machine are a helpful starting point, but no two lasers perform exactly the same. Fine-tune to your machine for best results.