Stain for solid color in wood finishing

Solid color finish (opaque color) requires a different finishing system with the transparent color. The stain for solid color is designed to cover the underneath surface and forming the desired color. Since that a solid color stain has different properties with a wood stain that is used for transparent color. The solid color stain is made from pigments to form the color and mixed with the kind of clear coating material as a binder. Pigment used is usually an inorganic pigment that has covering properties better than an organic pigment. The type of clear coating that is used can be various kinds such as PU, NC, AC, Water based, UV, etc. The type of clear coating in the mixture will determine the basic properties and characters of the stain.
According to his function, the solid color stain could be classified into three types:  base coat, enamel and toner. 
 Base coat stain. 

Base coat or primer color stain is a stain that is made by mixing pigments with a kind of sealer as a binder. Base coat has particularly similar properties with a sealer, but it has color in it. Base coats are usually applied directly on raw wood as the first color on the finishing system. Base coat containing a sanding agent that makes it easy to be sanded, but can not form a smooth surface and good flow film layer. There are many types of base coat depend on the clear coating in the mixture such as: UV base coat, PU base coat, NC base coat etc. The application of base coat is always in need of good sanding and followed by the application of other clear coatings thereon. Sometime base coat is also applied on the sealer, but the base coat layer always need a clear coating applications on the top of it. For finishing looked that require flat surface, the application of base coat to the raw wood would be an advantage because it can help to detect the defect an imperfectly preparation in he  wood surface. Uneven wood surface and small holes or dents will be more obvious with a colored layer of a base coat application than the no color clear sealer coat application. By this way the sanding and the touch up to fix the problem can be done more accurately. 

Enamel 

Enamel is slightly different solid color stain with the base coat; enamel is made from a mixture of pigments with a kind of top coat clear coating. Enamel is not equipped with a sanding agent but it is made to flow more evenly and more subtle. This enamel is relatively difficult to be sanded, but can be applied as a last layer on a finishing process. Enamel stain is usually applied over a sealer or base coat or surface that is already flat and smooth. Application of enamel on the rough surface will result an uneven coloration, while the sanding process for enamel is rather difficult.

The enamel is also equipped with matting agent to form the finishing gloss of the coating produced, but usually the resulting gloss of the enamel can not be highly precised. To obtain a more precise gloss in the finishing result is better done with clear top coat application in the last layer.

step panel for transparent solid color finish

Toner 

The toner is a stain that can also be used to create a solid color on the finishing process, but actually toner is more similar to the wood stain than the base coat or the enamel. The enamel or base coat is a pigment mixed with a clear coating in big percentage of a clear coating, while the toner is a kind of a wood stain which contains a small amount of clear coating. In enamel or base coat (this stain is also well known as a paint) the amount of pigment in the mixture is less than the amount of clear coating within the mixture. The number of pigment on a base coat or enamel is usually about half or less than the amount of the clear coating in the mixture. While the toner is of a stain with a little clear coating within the mixture. The number of clear coating in a toner is usually about 5% of the total mix of stain. Base coat and enamel is relatively thick layers of finishing like a top coat or a sealer, but the toner is a thin mixture as well as wood stain.

In a finishing process the toner is frequently used for finishing with a solid color that is still showing the character of wood such as the grain, pore and wood base color underneath. This toner has covering properties less than the base coat and enamel. Even toner can also be used for make a fully closed solid color, but it not effective since it need to do with combination with sealer or top coat and need many times application.
The selection of base coat stain, enamel or toner on a finishing process must be done accordingly with the clear coating used on the entire finishing system. The use of solid color stains that does not fit with the clear coating on it can cause problems in the finishing. When we have to use the base coat, enamel or toner different with the different type with the clear coating, the appropriate combination it should be chosen ( you can view it in my previous article the clear coating application in the wood furniture finishing). The simple rule is we consider the base coat, enamel and toner as a clear coating.


  
Paint Technology Handbook