How to prepare an image to laser engrave on slate?

Normally, an image with a high contrast ratio would look good after engraving on the slate.

However, other image-processing tips will help you to visualize the engraved image vibrantly.

Apart from the high contrast, there are technical issues such as dithering, inversion, and grayscale conversion to make the perfect image for slate engraving.

This article will focus on all of these steps to prepare the best image for your slate engraving project.

So, let’s begin.

Your first task is to get a powerful laser machine for slate. Then follow our image processing guidelines.

Choose the right image

Images with a lot of details do not look good when engraved on slate. Especially, if the subject and the background are similar colors then the engraved result would look messy.

Imagine you’ve got a photo of a pet, a bright-eyed dog with a dark coat. This is perfect for slate engraving because the contrast is naturally high. You want images where the subject pops against the background.

Another example could be a single-colored image without a background. See the below slate engraving.

The beer barrel and the writtings are in the same color tone which made an amazing contrast with the black slate.

Slate-engraving-tests-using-xTool-S1

To adjust the contrast of your image using Photoshop, follow the steps below:

  • Using photoshop, open the image you want to engrave by going to ‘File’ > ‘Open’.
  • Go to the ‘Layers’ panel, right-click on the background layer, and select ‘Duplicate Layer’. Name it if you want, and click ‘OK’.
  • With your duplicate layer selected, go to ‘Image’ in the top menu, hover over ‘Adjustments’, and then click on ‘Brightness/Contrast…’.
  • From the Brightness/Contrast panel, you’ll see two sliders. Ignore ‘Brightness’ for now and focus on the ‘Contrast’ slider. Slide it to the right to increase the contrast. 
  • Preview the changes and apply them.

Remember, there’s no one-size-fits-all setting for contrast as it greatly depends on the original image.

It’s always best to eye it and adjust accordingly. That means you need to develop of sense to adjust these image settings to get a proper engraving result.

If you find that you’ve overdone it, you can always step back by pressing ‘Ctrl+Z’ (Cmd+Z on a Mac) to undo it.

Make a grayscale version

Since color won’t be reproduced in the engraving process, convert your image to grayscale. This step simplifies the image and allows you to focus on contrast and detail.

In the same app, go back to ‘Image’, then ‘Adjustments’, and select ‘Black & White’. This strips away color, leaving you with shades of gray. It’s like prepping your photo to think in slate – no colors, just light and dark.

Here’s a detailed guide about the considerable issues on stone laser engraving.

Sharpening the detail

Apply a sharpening filter to your image to enhance the edges and details. This step will help in preserving the details when the image is engraved.

To do this, find the ‘Sharpen’ tool, or go to ‘Filter’ and select ‘Sharpen’. Use it sparingly; think of it as adding a pinch of salt to bring out the flavors in a dish.

Apply dithering effect

Dithering is a technique used to create the illusion of depth and shading by varying the density of dots. Most engraving software has a dithering option, which is preferred over grayscale for translating shades into engraving patterns.

You can apply dithering using a laser engraving workspace like Lightburn.

When saving your image, look for a ‘Dithering’ option, usually in the advanced settings of your engraving software. It’s a bit like turning a smooth gradient into a pattern of dots for the laser to follow.

Try removing the background

If the image has a complex background, consider removing it. The focus should be on the subject that you want to engrave.

To remove the background using Photoshop. click on the ‘Magic Wand’ tool or ‘Quick Selection’ tool. Click on the parts of the background you don’t want, and press ‘Delete’. It’s like clearing away clutter to showcase your main object.

There might be other ways of removing the background. However, we included only the Photoshop option.

Try an image inversion

Depending on the type of slate and the effect you want to achieve, you might need to invert the image so that it is engraved correctly. In some cases, what is dark in the image needs to be light on the slate, and vice versa.

For example, we inverted the following image before engraving it on the slate.

Slate-engraving-in-OMTech-Polar

If your engraving comes out too light, you may need to invert the colors. Click on ‘Image’, select ‘Adjustments’, and then ‘Invert’. Your image will now look like a photo negative, which can be engraved more clearly on dark slate.

What Lightburn settings would you set for slate engraving?

Preparing an image will not give you the best engraving result unless you set the right parameters in your workspace.

Below is a standard Lightburn setting for slate we found best. However, you may try the default slate engraving if it is available at your laser machine. We saw the XCS’s default slate engraving works great for the S1.

Here’s the optimum Lightburn settings for slate engraving:

Power: At or above 60%

Speed: 250 mm/second

DPI: High (at least 300 DPI)

Pro tip: Apply machine oil on the surface of the slate after finishing the engraving. It will give you a high-contrast visual of the engraved slate.

Remember, you cannot apply the same settings for any laser. Depending on your laser machine, you need to tweak it a little bit.

Conclusion

Slate engraving is the easiest laser work I’ve ever seen. The main art here is to prepare the image. If your image is properly adjusted per our guidelines, you will surely have an excellent result at the end. But, do not forget to apply machine oil to bring more contrast.

Ethan Robert
Ethan Robert

Hi, I'm Ethan.

After graduating from the University of North Dakota, I started knowing the CNC and that becomes my passion.

Earlier, I had fascination of 3d printers, Laser cutters and other CNC machines. Later on, I started analyzing those machine and started blogging on my known things by a different way.

I aim to assist you with the insights of 3d printer, laser engravers and computer printers with the help that you save your money and take the right decision before you purchase any machine.

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