The Secrets to Preventing the Yellowing of Engraved Characters: A Guide to Regulating Frequency Parameters

Yellowing of engraved material is a common problem for laser engravers. In this issue we explain the causes of yellowing, provide detailed adjustment steps and practical optimization tips, and help you to quickly solve the problem of discoloration, improving the clarity and longevity of your work.

Why does the ink on a seal turn yellow?

Many people have discovered that the characters they have just cut out turn yellow after a certain period of time. In fact, this is directly related to the laser frequency parameter.If the frequency is too high, the surface of the material will be burned, and plastics or acrylics will easily discolor.On the other hand, if the frequency is too low, the grooves may be too shallow, and the oxidation will make them even more noticeable.

Three steps to the best frequency parameters.

First, do a small-scale trial.

When experimenting with different frequency combinations, it is suggested that you begin with the recommended baseline values from the material manufacturer.For example, acrylic is usually used in the range of 20-30 kHz, while wood is used at 15-25 kHz.Each time, adjust the frequency by no more than 5 kHz, and observe the color change.

Observe the color of the markings.

I used a macro lens on my cell phone to take pictures of the results under different conditions.Under normal conditions, the grooves should appear uniformly gray-white; if there is a yellowish tinge or blackened particles, it indicates that the frequency is too high.At this point, the frequency should be lowered 2-3kHz to test again.

Combining speed and fine-tuning power.

High power can also cause yellowing.For example, if the original settings were 80 % power and 25 kHz, one could try changing to 75 % power and 28 kHz, which would slightly increase the speed of the laser head and prevent excessive heat buildup.

Tips for daily care.

Regularly clean the lenses.

If the lens is dirty, the laser will be scattered, causing a local temperature anomaly.If you wipe the lens with an alcohol-soaked cotton swab once a week, you'll see that the edges of the inscription are much cleaner.

Environmental humidity control.

Moisture in the air will accelerate oxidation of the material, so it is suggested that the humidity in the workshop be kept between 40 and 60 percent.In the south, users can place dehumidifiers next to the machines. In the north, users should warm up the machines for 10 minutes before using them.

After completion, the surface is treated.

After the carving is finished, the surface is wiped with a soft cloth dipped in polishing wax. This removes any remaining fragments and forms a protective layer.This is especially true of metal signs, which this technique can help to keep from oxidizing.

Special handling.

If you are engraving light characters on a dark material, the characters may turn yellow. Try using a lower frequency to engrave the outline, then a higher frequency to fill in the inside.This way, we can ensure clarity and reduce the overall heat buildup.