Material Testing

The first step of most laser cutting projects is material test.

If you’re new to laser cutting, you're probably wondering, What's that all about?

When I give workshops on laser cutting, the step I stress most is material testing. It's the step everyone wants to skip. We have this idea that because laser cutting is a mechanical process, we can simply enter in a factory setting, and—ta-da—amazing results. But would a painter use only paint out of the tube and never mix her own colors? Nope. Just like painting, laser cutting is an art, and creating the effect you envision requires experimentation.

This month I'm giving you a behind-the-scenes look at what goes into a material test. It's one of my favorite parts of the job, because it’s where new, innovative techniques come to light.

laser engraved whitewashed pine

Example 1: Who would have guessed?
One of the reasons to conduct material testing is that the heat of the laser can react with the material in unexpected ways.

Recently a client asked if he should whitewash his pine boards before or after engraving. Generally it’s better to apply the paint first, so it doesn't drip into the engraved area. And boy, am I glad we tested first. Who would have guessed the laser would turn the whitewash into black smoke that stained the board?

If the wood had been smooth, I could have applied a low-tack mask to protect the surface, but with the texture of the wood this wasn't an option.

laser engraved tests

Example 2: What effect are you looking for?
When it comes to engraving, a whole range of effects can be achieved, including different colors, depths, and edge qualities. Again, every material behaves differently. 

For this project, Paul Suntup of Suntup Editions was looking for laser-engraved belly bands for a limited edition of Stephen King's Misery. Here you can see the number of tests that went into the four samples he was sent to choose from. 

Example 3: Kerf
In the same way we account for the width of a saw blade when cutting wood, we have to account for kerf, or the amount of material the laser removes when cutting.

Kerf varies depending on the thickness and density of the material. It even varies depending on the size of the object! The kerf of a small cut circle can be different from a large circle. Yep, this is the craziness that goes into creating precision pieces.

Once the kerf is determined, the file is altered to reflect the loss. Even if your project doesn't require kerf adjustments, we still need to figure out the correct setting. We want a setting that will cut all the way through but isn't so powerful that it produces excess vapor residue or loss of detail.

adjusting for kerf creates a perfect fit for inlay

Laura Christensen - Regent's Park, 2018. Acrylic paint, vintage photographs, cherry wood, book cloth, and brass

FreeFall Artists in the World
Today we’re looking at a new work by Laura Christensen. By painting onto vintage photographs, Laura creates altered realities that are so seamless, it’s easy to believe they’re real. Material testing played an important role in Laura’s latest work, to create just the right ghostly effect she was looking for in the laser engraved panels.

She made this piece in response to Tears, Idle Tears, a 1940s short story by Elizabeth Bowen set in Regent's Park, London . The laser-cut design references a type of garden fence you might find in an urban community park. The design also echoes a motif in one of the photographs on the outside of the doors. 

Laura was looking to subtly engrave a garden fence into the cherry panels. The engraving is so subtle, in fact, that you can barely feel an indentation. Testing was done to find the precise setting that would give her an apparition-like look.

This is also a good example of how settings can even vary within the same species of wood. Laura's cherry was lighter than my shop sample. A very different setting was needed to achieve a similar result on the lighter wood.

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