How to Prevent Burning When Laser Cutting Wood

One of the most difficult things to deal with when laser cutting or laser engraving is trying not to leave burn marks around the laser’s path. Luckily, there is an easy solution to prevent burning when laser cutting wood with the right tools and a bit of patience.

When done just right, the results can look amazing! Let’s find out how.

Since the wood isn’t actually burning, you can use paper transfer tape or wood coating to prevent the surface from showing burn marks. Other methods include: sanding the wood after engraving, using air assist or adjusting the laser cutter settings.

What causes the burn marks?

Imagine an old brick fireplace in a cozy cabin that’s been around for decades. When you look inside, what do you see? Is it clean and polished? Or is it blackened and stained? Now imagine grilling a chicken in that fire, does it come out perfectly white and clean? Probably not. I’d say it would come out looking nicely grilled and a little charred (depending on your cooking skills).

So what causes the blackened bricks or the charred grill marks on the chicken? The bricks haven’t actually been burned and neither has the chicken so if you tried hard enough, you could actually wipe the stains off of the bricks.

Most charring isn’t actually from the material being burned but from the re-deposition of soot. Soot appears when burning anything organic. They are small carbon compounds that stick to surfaces that we don’t want them too.

That means that if we had covered the chicken in foil, it wouldn’t darken. Putting something between the brick and the fire would also stop the detritus from sticking on everything. This is pretty important to know because it actually gives us the information we need to get rid of the soot on wood when laser cutting.

Methods to prevent burn marks

Method 1: Use paper transfer tape

Although a lot of folks initially try to use masking tape to solve their problem (which can work), paper transfer tape (also known as application tape) works much better and you can get wide rolls of it.

This method stops the fumes from depositing soot on the surface of the wood and it is fairly easy to prepare.

If you want to keep the other side of the wood clean, you’ll want to apply transfer tape to the other side as well.

Check out Trotec’s video on how to use paper transfer tape:

Using a piece of plastic to flatten the tape works just fine but if you want to get really pro, then a small plastic squeegee works even better. Using a plastic squeegee makes it easy to evenly distribute the tape while making sure there aren’t any air bubbles, which can make the cutting results even worse.

One of the downsides to this method is that you would need to peel all of the tape off afterward which can be time-consuming if there are a lot of centers to pull off. Plus, all of the tape may not come off in one smooth stroke.

To deal with this, you can use a plastic razor blade to get under all of the tape quickly and easily, which would have saved me a lot of time had I discovered them earlier!

Another disadvantage some may experience with this method is that it takes longer to engrave or cut with lower wattage machines; so make sure you compensate or do more runs.

Method 2: Apply coating to the wood, then polish it

Another method I like to use is applying the coating before I laser cut or engrave to completely prevent burn marks from sticking to the wood, then wiping the burned residue off afterward.

Finishing the wood beforehand seals the wood and prevents the burnt waste from getting in the wood grains. Cleaning the mucky stuff off after is also way easier and smoother since it just slides off the coating.

Using a stain/coating that’s a different colour from the wood can also result in the engraved area having more contrast. Using this method can make your projects look even better!

After applying the finish and laser cutting/engraving, use furniture polish or some denatured alcohol to get rid of the burn marks effectively.

This method can be more time-consuming and more expensive than simply applying tape, but you could always buy finished wood to make the job quicker.

Method 3: Play with the laser cutter settings

Sometimes, all you have to do is make little changes to the speed and power settings. The laser cutting/engraving matrix that we use to find the perfect settings does a good job of showing us that there is an optimal range where there are fewer burn marks on the wood.

It almost seems too good to be true and that’s because it is. Finding the right setting to prevent burn marks when laser cutting can take ages. Using other methods may be more worthwhile.

However, If you can find the perfect settings and remember them, you have the quickest and easiest solution for future cuts!

Method 4: Sand the wood to remove the burn marks

Sometimes you gotta do what you gotta do. If there’s debris all over your project, then sanding it away is an easy fix.

I’ve always had a good experience using sheet sanders on my laser engraved projects (especially large ones) because it’s easy to add your own sanding paper and they’re fast and easy to control.

Using medium grit sandpaper should be enough to remove all signs of burning from the wood, and it’s important to make sure to follow up with higher grit sandpaper to leave a beautiful, smooth finish.

After sanding, make sure to blow out all of the dust, especially before finishing to get a clean final product. If it’s hard to get all of the debris out, then vacuuming works very well as well.

Method 5: Use air assist to blow away waste and fumes.

Air assist isn’t always guaranteed to prevent burning when laser cutting, but it definitely helps.

Since we should already be using air assist, it can help us prevent burn marks from appearing.

On the other hand, due to small differences in setup and air, sometimes it works for people and sometimes it doesn’t. For example, some makers will recommend that you use your air assist no further than 1mm over the wood with a large, pricey nozzle and others will say it’s not needed.

However, maximizing the use of the air assist is pretty difficult for beginners and can end up being pretty costly. Not only can the set up be expensive, but using specific gasses other than air can be dangerous.

Overall, using air assist effectively to prevent burning takes a lot of trial and error and practice, but you might as well use it because it will make a positive difference.

Other tips to prevent burning when laser cutting wood:

• Combine multiple methods for the best results!
• Pledge furniture polish before laser, then spray some on a rag to use for cleaning up. A coat of wax can definitely help with cleanup time.
• Use a cloth dampened with mineral spirits to clean wood surfaces.
• Some makers have gotten by with dampening their wood before laser cutting.
• Dish soap works well to clean for plastic and mineral spirits for acrylic.
• Black acrylic doesn’t show discolor.

Conclusion

Once we understand what our solutions are and practice a little bit of patience, we can easily prevent burning when we’re laser cutting/engraving on wood. If you use any one of the methods above or a combination of them, I can guarantee that your results will look amazing!

There are also different methods that other Makers are using right now, so if you are one of them, be sure to let us know what it is!