Wiping Filler for Wood finishing

Wiping filler is a type of filler that is applied by wiping. Wiping filler does not require a sanding process in its application. The process of cleaning the filler on the surface is not done by sanding but by wiping. This filler is very helpful to make a close-pore finish on wood, which has many pores and grain. Wiping filler is filling the grain and pores of the wood and coloring them at one time. This wiping filler is one of the modern finishing materials that is used, together with coating, to produce a beautiful, close-pore finish that still displays the beauty of the grain and pores of the wood.

Wiping Filler Function

• Cut process in finishing for close-pore finish

Wiping filler functions to fill the grains and pores of the wood. Wiping filler application will reduce the application of coating in the finishing process to a close-pore finish. The use of filler to fill the pores and grain of wood is highly recommended, since the coating material cannot be applied too much. Too much coating layer is costly and risky and can lead to crack problem.

• Coloring pores and grain

Wiping filler is available in a variety of color choices. When this filler fills the pores and grain, it will color the grain and pores of the wood. Wiping filler left in the pores and fibers of the wood can function like a glaze. Filler with a color that matches the color of the wood will create a natural wood-finishing appearance. Filler with a darker color will enhance the beauty of the pores and grain pattern of the wood. Filler can also be made with that contrasting color to produce a contrasting effect on the finishing.

• Reduces the risk of bubbles and pinholes

Finishing on wood with deep grain often causes problems off bubbles or pinholes. This bubble problem can be caused by the presence of air that is trapped in the wood pores or holes in wood. When a thick layer of finishing is applied to the wood, the air from inside the small holes rises and appears as bubbles in the finishing layer. When the bubbles are sanded and cut, then the result is pinholes at the finish layer. 

Wiping filler is one of the materials that can be used to reduce the risk of bubbles and pinholes. Wiping filler is a material with a fine bulking agent so that it can enter and fill small holes and pores in the wood so that there is no more air in the holes and pores of the wood that will cause bubbles.

 wiping filler application

This filler has physical properties like glaze but with a higher solid content. This wiping filler is thicker and more difficult to be wiped and cleaned than glaze. The application of wood filler is done by pouring it onto the surface, then spreading it with a cloth over the entire surface evenly. Make sure the filler has filled and covered the entire surface, then clean the filler with a dry cloth. Make sure the filler is only left in the pores and grain; excess filler on the surface needs to be cleaned since it triggers other finishing problems. Use steel wool or Scotch-Brite to clean the excess filler that has dried and cannot be cleaned with a cloth.

This wiping filler application can be done directly on the raw wood, but it is better done after the application of a wash coat (thin sealer). A wash coat is a thin sealer that is applied over wood or wood stain. The wash coat will raise and harden the wood fibers so that they can be cut by sanding to produce a smooth and clean surface. The smooth surface makes the wood filler can be wiped and cleaned easily and results in an even color. The application of wiping filler to raw wood directly risks getting uneven absorption of the filler due to the rough wood surface.

Make sure the filler is completely dry before continuing with the application of the sealer or top coat on top. Wiping filler is generally made as a complement of the NC system or PU system; therefore, it is made with a slow-drying oil thinner and does not dissolve the NC or PU layer. Wiping filler for the water-based system is made with a water solvent but is designed to dry slowly so that it can be applied easily. Therefore, it must be understood that this filler requires a longer drying time and must be fulfilled to avoid other finishing problems.

Actually, this wiping filler can be applied with a cloth with good results as long as the application technique is done correctly. However, for applications on wide and large areas, a special tool, a paddle wheel, can be used to apply the filler. This tool can help apply wiping filler for production with big volume. You can find more explanation about it in our previous post : Pedal wheel for wood filler application.

wiping filler application

Things to considered in the wiping filler application

• Filler cleaning

This filler must be cleaned properly so that it only fills the wood grains and pores. There should be no excessive filler and smearing on the surface because it will interfere with the appearance of the finishing and risk coming off the surface.

• Filler drying

The filler must be completely dry before being layered with a layer of coating on it. Fillers are generally made with oil-type solvents that dry slowly because of application concerns.  Therefore, this material will require a longer drying time. Check the drying time in the product data sheet and make sure you follow the instructions. The presence of oil solvents left in the filler and trapped by the coating layer will cause many problems, such as bubbles adhesion, and can even ruin the color and appearance of the finish

• Filler coverage

Wiping filler does not have as strong a coverage as “sanded filler” (regular filler that needs a sanding process). Wiping filler is designed with a finer material so that it can enter the pores and be wiped without having to be sanded. This filler is more suitable for handling small, deep pores but is not very suitable for filling big and shallow pores. Wood with small but deep pores, such as mahogany, sungkai, nyatoh, okumee, etc., often causes bubble problems. For that type of wood, the wiping filler works better because it can fill in and go inside of the small and deep pores. 

However, the wiping filler cannot perfectly fill wood with big and shallow pores and grain. The fine particles of the wiping filler cannot fully fill the pores and grain. The combination of "sanding filler" and wiping filler may be a good choice to make a close-pore finish. The sanded filler is applied to raw wood, while the wiping filler is applied after the wash coat to fill and handle the wood pores that are not completely filled by the first filler application. 

• Wood surface preparation

This filler application should be done on a wood surface that is smooth and sanded. The application of wiping filler on an uneven wood surface will potentially make the uneven coloring and blotchy look. The application of wiping filler is generally carried out after the wash coat as a substitute for the glaze application. 

• The color of the filler

This filler will color the wood fibers and pores and will eventually form the color of the finishing. Make sure the wiping filler you use can provide coloring according to the finishing color you want. The wrong filler color can ruin the appearance of the finishing you produce