Base Coat, the Finishing Material for Paint FInish

According to its name, the base coat is paint or coating that is used as the base layer in the first step in the finishing process. However, in wood finishing, base coat is usually referring to the finishing material that is used as a color-forming material for solid colors or paint finishes. A base coat is applied at the beginning of the finishing process to make color,  even though also has other functions such as: closing the pores and grain to make an even and smooth surface, or some other functions according to the type of the base coat. Base coat is one of the finishing materials that is widely used in wood finishing and furniture finishing and is also available in various types with their respective properties.

Base coat formulation

Base coat is made from pigments that is mixed with binder, a thick resin mixture as sealer or coating which is a material that forms a film layer. Thus, the coating results from the base coat will also produce a thick film layer like a sealer or coat instead of forming the color. 

base coat for golden white paint finish

Types of base coat

According to the type of resin, there are several types of base coats, such as : NC, PU, AC, Vinyl, water base, etc. Each type of base coat has different properties according to the type of resin used. In principle, the properties of the base coat will depend on the type of resin used. There are some types of base coat that are most used in the wood finishing process. 

• NC base coat

Is a base coat made of pigment material with a binder of NC resin as the main resin. NC base coat physically has properties like NC coating. It is 1 component material that dries with evaporation of its thinner, dries quickly, and is easy to be used and handled like NC coating.

• Waterbase base coat

Waterbase base coat is a paint with water as its main thinner. Like other waterbase paints, this paint is also available in various types, such as:  1 component waterbase base coat, 2 component waterbase base coat, oven dry waterbase base coat, etc. This waterbase base coat is the paint that is now widely developed by the paint industry to meet the desires of the community who want environmentally friendly finishing materials.

• PU base coat

It is a base coat with PU coating as binder. Because there are many types of PU, then there are also many types of PU base coats available in the finishing industry, such as PU exterior base coat, PU interior base coat, PU acrylic base coat, etc. This PU base coat has properties like PU coating; it is a two-component material that can provide a strong, thick, and hard film layer.

• Vinyl base coat

Vinyl base coat is base coat paint with a vinyl base. This paint is a finishing material provided to complement vinyl coating to build finishing on substrates that require a full vinyl system finishing system such as:  finishing on moving substrates or the special materials that need good adhesion properties.

Base coat colors

In the base coat formulation, pigment is added to make color of the base coat. Basically, all kinds of colors of base coat can be made to meet the needs of the finishing industry, but in general, the base coat colors available in the wood industry are not too many. The most common base coats are: white base coat, black base coat, and the basic colors. If needed, finishing industry players can mix to make colors according to the desired color needs.

Beside of the standard pigments, some special materials can also be added to the base coat to produce certain colors or effects, such as: gold powder, silver powder, aluminum paste, metallic color, etc.

Function of base coat

The function of the base coat is to form color and, at the same time, form a film layer on the wood surface. The application of the base coat will provide a film layer with specific color. The base coat layer needs to be dried and then sanded properly to make an even color and smooth surface. The application of the base coat also work to close the pores of the wood and produce a flat surface. The application of the base coat also raise and make the wood fibers hard and stiff. With good sanding, the wood fibers will be cut and result to a flat and smooth wood surface.

The base coat will also build color in the finishing process according to the color of the base coat. The base coat can be made in various colors according to needs by adjusting the pigment mixture in it. The coloring of the base coat will fully cover its substrate, meaning that the resulting color will not mix with the color below it but depends entirely on the color of the base coat applied on.

Base coats with special formulations can also be made for some specific purposes, such as increasing adhesion, anti-rust material (for metal materials), closing wood grain and pores, etc.

Application of the base coat

The application of base coat basically depends on the appearance and color of the finishing desired. Usually, base coat is applied by spraying to the entire surface evenly, although other ways of application can be used, such as: by rolling, brushing, sponging, etc. In most finishing processes, the application of base coat is continued with a sanding process to produce a flat and smooth surface. However, there are several variations of application that can be done to produce the required coloring and appearance.

• Base coat for solid colors

The base coat to build solid colors must be able to cover its substrate completely. A fairly thick base application is needed to cover the base color of the substrate underneath so that the resulting coloring can be stable. For this reason, a minimum of 2 layers of base coat application is needed, followed by good sanding for each layer to ensure that the base coat can cover the color of its underneath perfectly.

• Base coat for antique colors

For antique finishing, the base coat can be the object of the antique process. The application of the base coat can be followed by an antique process such as physical distress, sanded trough, washed off, and other antique processes. The base coat for this process may not have to be totally covering and thick but can be a thin layer, semitransparent according to the needs of the finishing process. The base coat can also be overlaid with special paints such as crackle paint, texture paint, etc. In addition, the base coat can also be made specifically to produce special effects such as cracked paint, textured paint, broken, etc.

• Base coat with thin coloring (semi-transparent)

In some cases, the base coat can also be made with coloring that does not totally cover its underneath. The base coat can be thinned so that when applied it does not completely cover the surface underneath but produces semi-transparent coloring. The resulting color is a combination of the substrate color and the base coat color.

Things to consider when applying the base coat.

• Layer thickness

The thickness of the base coat layer will determine the coloring resulted by this base coat. A thin base coat layer will allow the color of the substrate to appear and mix with the color of the base coat. In some cases, this will cause color problems. When you choose to use a base coat and form a solid color, of course you expect to get the same color in every part of the product and in every product you do. However, if the base coat application is not thick enough, and the color of the base coat cannot completely cover the entire substrate below it, then your color will affected by the substrate. When there is color variations at the substrates (which is often found in the wood industry), the color of the finishing will also vary. To overcome this, make sure that the base coat coating is done with sufficient thickness. To get sufficient thickness, at least 2 of base coat by spray wet coat applications are needed with a good sanding process on each layer.

• Base coat type

There are various types of base coats, and each type has different properties. Therefore, make sure you know the type of base coat you are using and recognize its properties. Thus, you will be able to use it with the most optimal results.

• Substrate type

There are many materials used in the wood and furniture industry. There are various types of wood, which has its own unique and distinctive properties. The wood and engineering wood has its character that may need different treatment. Make sure you know clearly the type of substrate and material you do, and make sure you recognize its properties and choose the type of base coat that is most appropriate for your needs. 

• Finishing step

Step panel is the important tool in the finishing process. For more information about the step panel, you can view our previous post: Step panel for wood finishing. Make sure you make a step panel first at the beginning of the finishing process to be able to determine the finishing processes needed with all its materials.