" " wisno wood furniture finishing: Top coat for furniture finishing

Thursday, October 1, 2009

Top coat for furniture finishing

Top coat is finishing materials that applied as the last layer in the finishing process. Top coat is usually applied over the sealer. Together with sealer the top coat forms the film layer in the finishing to cover and protect the finishing color. Top coat is usually applied in a clear state (no color), but it is also possible to applied in a mix with pigment so he has a specific color. The top coat that is mixed with pigment is called enamel or toner. The enamel and is usually used to make the solid color (opaque color) finish or paint finish. In the solid color finish, the enamel help to make the final color with shorter finishing step. The enamel can be applied as the final coating and he work to form the color and build the film coat in the same time. However the uses of clear top coat is highly recommended to make the good quality finish. The pigment in the top coat will affect the gloss and make the control to the gloss of the finish become more difficult. If we use the clear top coat then we can assign the top coat  just to make the smooth surface film and the right sheen.
In transparent color, top coat should stay clear without any colors. The colored top coat in transparent finishes will make difficulty in controlling the final color resulted. The colored top coat means that the top coat is wished to fulfill 2 functions in the same time, to form the color and to build a film layer.  It makes difficulty to control the result; if we want to get the right color, then we may spray too much or too less top coat which could make the uneven surface, gloss or rough film surface. While if we want the smooth surface, we may won,t get the right color.  For transparent color, the color should be built and controlled by stain application, and the clear coating is applied only to form film layer, then we can get better control for the flow, sheen and the feel.
Some peoples call the top coat with lacquer. Lacquer is actually the paint or resin solution that will dry and make a hard film by evaporation of his solvent. Lacquer is a material that was used as a top coat at the beginning when peoples started using coating to do the finishing. The lacquer was the first coating that replaced the shellac in the early 20th century. With the development of finishing materials and technology now there are lot of materials for top coat. The top coat now is available in many type, made of various resin that dry and cured by chemical reaction that cannot be named as lacquer.
As the final coat, top coat also designed to make gloss of the finishing. Gloss is one of the finishing look that is very important. Gloss is the measurement of the light reflected by the surface. The surface is called high gloss or sheen when the surface reflects large percentage of light that goes to him. A glass or mirror is the example of high gloss surface. While the surface is called low gloss is when the surface reflects small percentage of light that goes to him. Gloss or sheen is measured with gloss meter and usually scale from 0 for the lowest sheen to 90 for the highest. In furniture finishing the sheen of the surface sometime is also called in different way: high gloss, gloss, semi gloss, and semi doff and doff. High gloss is highest and doff is the lowest. There are also some peoples that call the sheen with %, the highest sheen (sheen 90) is called as 100%, while the lowest sheen (sheen 0) is called as 0%.
Lacquer or top coat is made of a mixture of resin with one or more dominant primary resin. The primer resin will determine the type of top coat and form the main character of the top coat. This resin mixture is then solved in his solvent to make fluid form. There is some additive materials are added to mixture to make some special properties that needed. Some additive materials for top coat are: surfactant, plasticizers and bubble breaker. Surfactant is a substance that makes the mixture becomes more homogeneous and will reduce the surface tension, it makes the resulting coating film becomes more even and smooth. Bubble breaker is material affecting the surface tension so that the surface is wet or open longer so make the air trapped in the coating film can be released into the air. Plasticizers is a material that makes the film formed to be more flexible and plastic. It used to make the finishing film is more elastic to prevent cracked in the finishing layer. To make and adjust the gloss of finishing then the top coat is added with matting agent or flattening paste. Flattening powder is made from an inert material such as silica dust that will spread the light in the film layer so that it will decrease the gloss of the resulting film layer. The amount of flattening powder in the top coat will determined the gloss of film formed with the top coat.

0 comments:

Post a Comment