Streak Spray Problem in The Wood Finishing.

Streak spray is the uneven spray on the finishing surface. In the case of thin spray streaks and for the low gloss finish, this problem may not be as visible. However, in severe streaks, it will appear as a zebra-like striped appearance at the finishing surface. It will make the finishing look bad, especially for the high gloss finish and the dark or black color. In the top coat layer, this streak will greatly disturb the look since the uneven gloss of the top coat layer. This problem will be more disruptive to finishing with high gloss and a big, wide, flat surface. In the objects with a small surface and low gloss finish, the vague streak might not be too visible.

Streak is not a real problem at the sealer application. Uneven surfaces on the sealer can be cleaned up with a good sanding process and recoated with a good layer coating on it. 

While in the stain application, the streak spray will result in uneven staining and appear as color-striped. It will be a problem finishing because it will produce stripped and uneven finishing color.

streak problem

The causes of streak spray and how to solve problems

Streak spray is the result of the uneven finishing material application. There are some things that can cause the uneven material finishing, and we need to parse them one by one to overcome this problem more precisely.

• Improper spray technique.

The correct spray technique could produce a finishing layer with an even and smooth all-over surface. The spray technique involves two things: the techniques of setting the spray gun and the techniques of moving the spray gun. Both must be done properly to produce the even and smooth coating materials. You can read about the technique in our previous article: how to use the spray gun correctly

•  Improper spray equipment.
  

To produce a perfect coating, good and proper tools are needed. Spray gun with small size (cup gun) is not suitable to do spray on the wide and big surface. You need the spray gun with a large nozzle to spray the surface with a wide and spacious field. The spray gun with the small spreading spray width will require too many strokes to spray the big and wide surface panel. The small-size-width spray will also make the perfect spray; overlapping is difficult to obtain.

To spray on the wide and spacious surfaces, the spray gun with a pump or pressure ports is recommended since it will make the job easier. The pumps or pressure ports will make the movement of the spray gun more freely than the cup gun that has a cup stuck on the gun.

• The imperfect material atomization

Perfect material atomization is the main requirement to produce the even and smooth coating layer. Make sure that the material can be perfectly atomized in the spray application. Check the condition of the spray equipment; make sure that the nozzle, needle, and cap are clean and in good condition.

Check the viscosity of the finishing material and adjust according to the spray equipment specifications. Finishing materials with too high viscosity will result in imperfect atomization. Add some thinner if necessary to reduce the viscosity; make sure that the viscosity of the material fulfills the spray equipment specification.

• The finishing material that is dry too fast.

Coating materials need to dry together to produce an even and smooth surface. Each next spray gun stroke has to be done when the previous stroke layer is still wet to make each layer blend well. Therefore, the finishing material should not dry too fast.

Make sure that the layer of finishing material is still quite wet when the spraying process on a certain object is done. Adjust the finishing material according to the spray application. Add some thinner retarder to the mixture if necessary.

How to revise the results of the spray streak problem.

Steak spray will become a finishing problem only when it disturbs the finishing look. At the top coat layer, the streak appearance can be cleaned by sanding the top coat layer well and then re-coat the top coat with good technique.

Streak spray on the stain will produce an uneven color in the finishing. It should be corrected. The uneven stain should be removed by washing off with thinner. Washed off the uneven stain and cleaned off with paint thinner until an even color and clean surface are obtained. We may need to resand the wood surface. Then we need to reapply the stain to make the color.