Marring Problem at The Wood Finishing

Marring is fine surface scratches at the surface. Marring generally is distributed over a relatively large area that typically spoils the appearance of a surface coating. People are easily confused between mar and scratch. Both marring and scratch resistance are considered to express the strength of the finishing layer. When they find mar problem at the finishing layer, then they think that the finishing is not strong enough, and they ask for stronger finish. But actually, mar and scratch are two different things. Mar-resistant actually is not really related to the strength of the finish layer as the scratch-resistant. Marring is the fine scratching on the surface and only gives effect to the surface finishing layer without affecting the body of the finishing layer. The marring problem will not disrupt the protection function of the finishing layer but only ruin the appearance of finishing. While the scratch involves to the entire finishing body and damage to the whole body of the finishing layer. The scratch problem sometimes could make the substrate open and will affect the protection function of the finishing layer. Scratch resistance is highly dependent on the strength of the finishing, especially the adhesion and hardness of the coating film. While the mar resistance is still affected by the hardness of the finishing layer but actually is more dependent on the “slippery property” of the surface. 

mar at the black finish

Although it will not really affect the strength of the finishing layer, marring is still considered a problem in the finishing, especially when we deal with high-end products. The good finishing layer is always expected to have good mar resistance; any mar problem at the finishing will ruin the finishing appearance and then lower the finishing quality. 

Here are some things that we can do to avoid marring problem at wood finishing.

• Use the hard coating layer.

Marring resistance somehow is still related to the hardness of the coating layer of the finish. The hardest the coating, then the less risk to get a mar problem. The fact is the problem is often found at the finish that uses 1 component coating that is relatively "soft." With the pencil hardness test, the 1 component coating (NC, water-based, shellac) will give HB or B score that is relatively low.

To avoid the mar problem, we can apply the harder coating to the finishing. We can use the 2 component coatings, such as AC or PU coating, or UV coating. The PU or AC coating that dries with the chemical reaction will give 1H or 2H with the pencil hardness test will surely give harder film layer and will reduce the risk of mar problem at the finishing. The UV coating is even one component, but it is dry with chemical reactions and could give the harder coating layer; then the PU or AC coating will also give better mar resistance to the finish.

• Apply wax at the finish surface

Instead of the hardness, mar is highly dependent on the slippery property of the surface. The smooth and slippery surface will make any force received by the surface "slip” without leaving scratches. Some finishing material manufacturers have provided fluid lubricant that can be applied to the finishing surface. The material usually is liquid-contained wax that works as a "lubricant" to add "slippery" properties at the finish surface. The liquid can be applied to the top coat after the top coat is dry. The wax can integrate with the coating to increase the slippery property of the coating surface and help to minimize the risk of mar problems at the finish.

• The choice to the color and appearance of the finishing.

Marring is associated with finishing appearance. The fact is, mar problem usually appear at the finish with dark colors. The risk of getting a mar problem will be higher if we use the extremely gloss (very high gloss or very low sheen). The finishing with NC system may not get mar problem for the white or light brown color. But we will get the mar problem for the dark brown or black color, full gloss, or dead matte finish, even though we run the same material and the same system.

Actually, with the same system and same coating type, the finishing layer will have the same strength and hardness. At the light brown or white color, actually there is mar (fine scratches), but it is difficult to see and tends to be invisible. While at the same scratches at extremely dark color, high sheen or low sheen will obviously seem and then be detected as a problem. Based on this fact, every time we finish with dark color and an extremely high or low sheen, we must consider the mar problem risk. We may need to consider using the hard coating layer or doing special treatment to minimize the mar risk.

• Use standard testing to observe the mar resistant

Sometimes the mar is very easy to happen. The fact is we don’t need hard power to make mar. The hard material, such as nail tip or even dust at the surfaces, will easily create scratches to finish surfaces without any strong energy. Even the strongest coatings, such as PU or even the UV coating, are actually easily scratched, so when we observe the mar resistant to the finish, we should use the standard test (we can refer to http://www.astm.org/Standards/D5178.htm178 - 13). Any test with a nail, finger, or other method cannot be used since it won't give a measured result.

Then finally, we always need to refer the marring resistance of the finishing to the standard coating properties. We need to realize that every type of coating actually has limitations, and we should not expect the finish strength to exceed its natural properties.