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Laser Engraving Granite: Expert Guide

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John Abraham
Hey I'm John. I write about Manufacturing, Metalworking, CNCs and Lasers at Mellowpine. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com

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Laser engraving granite

Laser engraving can be used to customize granite with designs, text, or images that can last a lifetime.

But if you are planning to laser engrave granite, you must be aware of the challenges it can put forth and how to tackle them.

This article discusses the process of laser engraving granite and its applications.

I also discuss the factors that affect the engraving quality.

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Laser Engraving Granite- The Process

Laser engraving on granite can be performed by using a moderately powerful CO2 laser (above 60W).

Generally, polished granites are used for laser engraving because the laser removes their shiny-polished surface, revealing the dull layer underneath.

Furthermore, black granites produce the ideal results with high contrast gray-white engravings.

The process of laser engraving granite consists of a few basic steps.

ParameterRecommendation
Type of laserCO2
Laser power40W and above
Engraving SpeedHigh-speed multi-layer engraving
Spot size0.25mm – 0.5 mm diameter
Air assistA low-pressure air assist is recommended
Exhaust systemRequired to effectively remove the dust

Recommended parameters for laser engraving Granite

If you are looking for laser engraving granites using a diode laser, watch our detailed video for valuable insights to get the best results.

YouTube video
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Step 1: Optimize the Design

The first step in laser engraving a photo on granite is to prepare the design. You can use any standard CAD software like Adobe Illustrator, Inkscape, CorelDRAW, etc.

For granite engraving applications, it is recommended to limit the image data to the important parts. It can be a person in the image or any other object.

This can be achieved by following the below-given steps to customize the design.

Steps:

  1. Remove the unnecessary background
  2. Increase the image contrast
  3. Covert the image to grayscale
  4. Invert color to make it a negative image
  5. Adjust the contrast
  6. Make final adjustments
  7. Export the final image
CAD process in engraving granite - Grayscaled image (left), Backgrounds removed (middle), Negative image (right)
CAD process in engraving granite – Grayscaled image (left), Backgrounds removed (middle), Negative image (right)

Inverting the color to produce a negative image is generally used when engraving dark granites.

Laser engraving on black granites produces a high-contrast white mark with a black background, which resembles closely a negative image.

In most other laser engraving applications, like laser engraving wood, we work on light-colored objects where black engravings are produced. In such applications, inverted images are not needed.

Step 2: Prepare the Workpiece

Before executing the process, make sure the work area of your laser machine can handle the weight of the granite slab before placing it.

If you are working on large blocks of granite thicker than 2″, it is advised to use an independent leveling system that can carry large weights and level the workpiece perpendicular to the laser beam path.

Clean the granite surface to remove any pre-existing stone dust, as it can reduce the intensity of the laser beam reaching the granite surface.

Step 3: Execute the Engraving Process

Once you prepare the design, set the optimal parameters and execute the process.

Multi-layer engraving gives better details on granite as you can engrave important texts and shapes comparatively deeper than the rest of the engraving, by using the multi-pass technique.

A laser spot size between 0.25mm to 0.5 mm in diameter is a good option for performing engraving operations on granite.

Also, a low-pressure air assist with the support of an exhaust can help effectively remove the generated dust from the workpiece surface during the job.

Laser Power
(Watt)
Output Power
(Percentage)
Speed
(ipm)
No. of Passes
40W85%238.5 ipm1
60W85%283.4 ipm1
65W40%649 ipm1
80W85%354.3 ipm1
100W25%649 ipm1
150W18%649 ipm1

Speeds and Feeds chart of engraving granite using a CO2 laser

Step 4: Post-Processing

After completing the engraving process, the granite slab will be covered in dust, and you have to clean it off first.

Then you can give it a chemical wash using denatured alcohol to remove fine dust particles trapped inside the engraved trench.

After cleaning the surface, you can apply a layer of paint all over the engraved part to highlight your engraving.

The rough, porous nature of the engraved granite surface facilitates the bonding of paint to the granite surface.

Laser Engraving Granite – Factors to Consider

1. Color – Black is Better

Black galaxy granite
Black galaxy granite (Source: International Granites)

Black granites are generally used for laser engraving because the engravings on them will have a highlighted look.

Special laser-grade super black tiles, which are generally priced a little higher compared to the regular black granite, are ideal for different types of laser engraving applications.

However, you can also use regular general-purpose granite, like black galaxy granite, that has a fine grain structure and produces high quality engraving outputs.

2. Grain (Fine grains = Great Details)

Granite grains
Granite grains (Source: Marble and Granite Connection)

When selecting granite for laser engraving applications, it is recommended to choose one with fine grains.

Rough grains of a granite interfere with the engraving design and reduce the detail in the engraving.

3. Fossils/Veins

Granite veins
Granite veins (Source: Texas Granite Group)

Fossil bugs and vein whites in granite can negatively influence the details in an engraving.

Some granite have hair-thin trails, while others have trails over a broader area.

These generally have an irregular appearance, and it is recommended to choose granite that does not have any visible fossils or veins.

4. Composition

Granite is mainly composed of quartz (10% to 60% by volume) and feldspar.

If you are engraving granite for outdoor applications, choose one with a higher quartz content as they are hard and durable.

5. Surface Finish

Black Zimbabwe polished granite
Black Zimbabwe polished granite (Source: Southland Stone)

As a general rule, stones with smooth or polished surfaces give good results when laser engraved.

When selecting the granite for your application, it is advised to look for granite with a smooth surface finish, as it produces high-quality engraving results and makes your post-processing process much more manageable.

Final Thoughts

With a good laser engraver and optimized design, you can produce high-quality engravings on granite.

Black fine-grained granites produce the best results for laser engraving, with no or minimal post-processing requirements.

Engravings performed on granite are wear-resistant and long-lasting, making them suitable for outdoor applications.

It must be noted that minerals like quarts and the polished surface of granites can reflect the laser beam which can be dangerous if comes in contact with the eyes.

Therefore, it is recommended to wear appropriate laser safety glasses and strictly follow the laser safety protocols when laser engraving granite.

Laser Cutting and Engraving Other Materials

Following are some detailed guides on laser cutting more materials.

MaterialLink to Guide
PaperLaser Cutting Paper
AcrylicLaser Cutting and Engraving Acrylic
AluminumLaser Cutting and Engraving Aluminum
LeatherLaser Cutting and Engraving Leather
PlasticLaser Cutting and Engraving Plastic
PolypropyleneLaser cutting polypropylene
BrassLaser Engraving Brass
FabricLaser Cutting Fabric
FeltLaser Cutting Felt
FoamLaser Cutting Foam
Wood (cutting)Laser Cutting Wood
Wood (engraving)Wood Laser Engraving
PlywoodLaser Cutting Plywood
Glass (cutting)Laser Cutting Glass
Glass (engraving)Laser Etching and Engraving Glass
GraniteLaser Engraving Granite
VinylLaser Cutting Vinyl

Laser Cutting Guides for other Materials

Frequently Asked Questions

What are the different types of stones a laser engraver can work on?

A laser engraver can work on stones like slate, basalt, pebbles, ceramic, sandstone, granite, limestone, marble, and similar stones. However, the stones which give good contrast when laser engraved are granite, marble, and slate.

Which laser machine can engrave granite?

Granite can be engraved using fiber, CO2, and even a diode laser. But for engraving with high quality and detail, a CO2 laser with powers ranging between 40W – 80W is the best option. Diode lasers are not that effective, and it takes more than five times the time taken by a CO2 laser to do the same job.

How long does laser engraving on granite last?

The engravings on granite can last for a long time, even until the granite completely weathers off. When kept in external climatic conditions, the engravings can fill up with dust, moss, etc., gradually covering the engravings. A single wash can easily recover such engravings if they are post-processed with sealant paints.

John Abraham
Hey I'm John. I write about Manufacturing, Metalworking, CNCs and Lasers at Mellowpine. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com