Get Rid of Laser Burn Marks: How to Laser Engrave Wood Without Burning

From time immemorial, wood has always been man’s favorite material for production and construction. The natural abundance of timber, as well as its simple workability and longevity, have proven it extremely advantageous in many applications. Wood is also convenient to mark with desired patterns, text, logos, etc. While hand carving, painting, and burn marking have been used throughout history, in recent times, laser engraving wood projects are gaining prominence. In fact, wood is a staple material among the laser engraving community.

Nowadays, engraving wood is a lucrative venture for businesses and a leisure act for hobbyists. In fact, many CO2 laser machines have been specially made to carry out wood engraving. Despite the suitability of CO2 laser machines for engraving wood, lasers can sometimes leave behind burn marks as collateral damage. Burn marks can leave an unsightly stain around your otherwise beautiful wood engravings, and give your job a poor finish. Learning how to laser engrave wood without burning is a skill any laser woodworker must acquire.

In this article, the causes, preventions, and corrections of burn marks will be discussed to educate you appropriately. Keep in mind there any many several ways to engrave wood, and there are various types of wood that absorb laser energy differently. You should always expect some trial and error when it comes to laser burn marks on wood—especially when using a new type of wood. OMTech laser specialists will provide some key tips and tricks on how to get rid of laser burn marks, so you end up with a block of clean, engraved wood without the extra hassle. Now, let's dive in.

Causes of Laser Burn Marks on Wood

There are two main causes of burn marks while engraving wood, and they are:

EXCESSIVE HEAT AND DEBRIS

Out of the many ways to engrave wood with a laser, all of them require heat generation by laser energy. Nonetheless, excessive heat application with the intent of quickly finishing the job will mostly turn out detrimental.

It is more dangerous when debris on the wood's surface combines with the laser beam's excessive heat. Therefore, these two complementing factors must be looked out for before commencing wood engraving.

CONTACT WITH THE LASER BED

The CO2 laser machine structure could affect the occurrence of burn marks, most especially on the reverse side of the wood. Specifically, thin woods are the most prone to burn marks due to contact with a laser bed. Hence, the laser bed must be such that it allows for easy dissipation of heat/fumes generated while engraving wood. There are four forms of laser beds which are:

1. Honeycomb Cells
2. Aluminum Lamella
3. Aluminum Engraving Table
4. Aluminum Knife

Generally, you must understand the nature of the wood you are working on to decide which laser bed is best for you. Testing our multiple workbed styles could teach you how to laser engrave wood without burning. The standard honeycomb beds on most OMTech CO2 laser machines offer good heat dissipation and should work well with most woods.

Prevention: How to Laser Engrave Wood Without Burning

As they say, "prevention is better than cure.” Similarly, it’s better to learn how to laser engrave wood without burning, rather than focusing on how to get rid of laser burn marks after engraving. Most laser burn marks can be avoided while engraving wood by any of the following methods:

USING LASER ENGRAVING MASKING TAPE FOR WOOD

Applying laser engraving tape for wood prevents fumes from leaving smut on the wood by masking the wood surface throughout the engraving process. Also, any air bubble must be smoothened using a plastic piece to prevent even worse burn marks. Once the wood engraving is done, you can remove the transfer tape using a plastic razor blade to make the process easier and faster. Apparently, the stains are peeled off the wood with the tape and the wood surface is left clean from burn marks.

Lastly, try to find a laser engraving tape for wood with the right amount of tackiness. For example, birch plywood has such a high moisture content and uneven grain structure that after a few minutes, and even during the engraving process, the backing can peel off, making it look much more burnt than if it was not used at all.

Since there are many ways to engrave wood, you might benefit from buying a few different types of laser engraving tape for wood in low quantities to test them out.

ADJUSTING THE LASER ENGRAVER SETTINGS

It is only imperative to make small changes to the speed and power settings of CO2 laser engravers. There is a top range, which, when applied, can greatly reduce laser burn marks on wood. This is usually discerned from adjusting the settings from time to time to get the optimal range. The best way to engrave wood and prevent burn marks is to use the fastest speed setting in the optimal power range for a given type of wood.

First, increase the speed. Then, increase the power until you find the perfect settings.

An important parameter that can be adjusted to give optimal results is laser focal distance. If the best distance of laser focus can be determined, this will greatly reduce the burn marks while allowing for smooth results. Trying out various focus settings would help you achieve this.

USING COMPRESSIVE AIR ASSIST

Air assist does not always get rid of laser burn marks completely, but it definitely helps. This involves applying compressed air at the engraving spot as the laser fires. The optimal usage of air assist is quite difficult for beginners and can be pretty expensive. Apart from the setup being expensive, using gases other than air can be risky. The optimal air assist usage helps get rid of laser burn marks. While engraving wood involves a ton of trial and error, but utilizing a proper air assist system is one of the best ways to engrave wood (and cut wood) more effectively.

COMPARING DIFFERENT WOODS IN ADVANCE 

Learning how to laser engrave wood without burning could be as simple as trying a different type of wood. Some woods are much more susceptible to getting laser burn marks than others. This difference is not a result of any inherent property of woods but due to glue binders rooted in these woods. The glue binders aid burning and create more fumes and burn marks while engraving wood.

Therefore, it is imperative to test different woods for speed and power to reduce burn marks on woods. Examples of wood with glue binders rooted in them are Plywood and MDF. Other woods such as Basswood, Cherry, and Alder are great woods for laser engraving.

DAMPENING THE WOOD BEFORE LASER CUTTING

This simply involves briefly soaking the wood in water before laser engraving commences. This does not inhibit the laser's performance; instead, it can hinder or even completely get rid of laser burn marks. Burn marks are caused by excessive heat, and moisture helps the wood remain cool while absorbing the laser energy. Soaking your wood in water is just another method to laser engrave wood without burning.

Correction: How to Get Rid of Laser Burn Marks

If you’ve already processed your wood and are still left with burn marks, you can still remove the burns. Learning how to get rid of laser burn marks post-engraving can sometimes be just as important as taking preventive measures.

SANDING

Sanding can be done using sheet sanders. These are fast and easy to control. Medium grit sandpaper can sufficiently remove all the burn marks, but it is important to use higher grit sandpaper afterward to leave a nice, smooth finish.

If you’re dealing with finely detailed engravings with minimal depth, it’s important to sand very lightly. Removing too much of the wood can undermine the distinctive beauty of your engraving. It is also important to blow off all the dust before finishing to get a smooth and clean final product.

APPLICATION OF COATING

This method works best with finished woods. It involves coating the wood with a color different from the wood's so that the engraved area has more contrast. Applying the coat before engraving may not get rid of laser burn marks completely, but it helps prevents burn marks from getting stuck to the wood. The marks can be easily cleaned off using denatured alcohol or furniture polish to rid the wood off of burn marks completely.

SLIGHT SCRUBBING

You can generally use a toothbrush or fabric brush alongside liquid soap to scrub the burn marks mildly.

Conclusion

By now, we believe you should have a clearer picture and broader knowledge of how to laser engrave wood without burning. It’s always best to take preventive measures before engraving, rather than having to get rid of laser burn marks after engraving. Here at OMTech, we offer the best desktop and cabinet CO2 laser machines suitable for engraving all kinds of wood species. If you also desire to test the machines before purchasing, our Southern California showroom is always open during work hours. Do well to partner with us on your next engraving project to make it a success.