Swirl Marks Problem in Wood Finishing.

Swirl marks are the problems in the wood finishing process. Swirl mark appears as the swirl or spiral on the wood surface. It will appear more clearly when we apply wood stain to the wood surface. The more stained wet wood, the more swirl marks will be apparent. Swirl marks will also be very visible when the glaze is used at the finishing system; the glaze will fill and color the swirl and be clearly visible at the finishing result.

Swirl mark problem is caused by the improper sanding process by the hand sander. The palm sander and rotary disc sander, if not properly used, will cause the swirl mark. Swirl marks won’t happen when we sand using the big sanding machine, such as a stroke sander or wide belt sander. The swirl mark is mainly happens when we press the sanding machine too strongly on the wood surface in the sanding operation. It often happens when we use the blunt sandpaper or too fine sandpaper to sand the rough and wood surface. 

lamp for sanding check

 
Here are some tips to handle the swirl marks problem.

• Make sure the sanding machine is in good condition.

The palm sander works by vibrating the sandpaper, while the disc sander works by rotating the sandpaper. Both movements are causing friction with the sandpaper on the surface of the wood. To produce a good sanding result, we need stable movement. The unstable movement will cause problems in the sanding result. Put the sandpaper at the pad and run the machine and feel the movement. The sanding machine must be able to move and run stable and controllable easily. Stop using sanding machines when we feel the movement is “wild” and unstable. Fix the sanding machine first and make sure the machine is in good condition when we run the machine.

The second problem that is often found is the pad. The pad is used as a place to attach the sandpaper that is moved by the machine. The pad needs to be thick and “elastic” enough to reduce the excessive pressure during the sanding process. Check the pad condition and make sure it is flat and thick (elastic) enough. The thin and uneven pad tends to produce excessive pressure on the sanding process, which is the main cause of swirl marks.

• The proper sanding technique.

Hand sander machine is small machine but effective and helpful to do sanding for small stuff or small area. It is portable, handy, and flexible, with good results. However, this tool will only work well if we use it properly. The key is: don't press the machine too strongly. Let the sandpaper do its job to sand and scrape the wood surface. Just make sure we use the right grade of sandpaper and use the sharp sandpaper. The sandpaper that has been blunt must be replaced because it does not work well. Do the sanding process patiently, little by little, and use the sandpaper grade by grade from the coarse to the finer; never skip the grade sandpaper. If we push the machine too much, then we tend to press the machine to hard, and it will create the swirl mark. (See our previous article : pad sanding machine.)

• Checks the sanding before starting the finishing process.

Swirl marks should be addressed and corrected before the finishing process is done. The revisions and repairs after finishing the process will be a hard and costly process. We had to remove the finishing layer, resand, and do the refinishing, which is difficult, expensive, and never gives a perfect result. Use the light or thin stain to help check the sanding quality at the beginning of the finishing process. (See our previous article : the wood sanding.)

• Selection of the finishing color and appearance.

Swirl marks will be apparent in a transparent wood finish. Swirl marks may not be visible for finish without wood stain or glaze application. We may obey the swirl mark for paint finish or natural finish, especially when the finishing quality requirement is not too high. Although the swirl mark is considered an indication of the wrong wood sanding process, for some finishes we may continue to do the finishing.