" " wisno wood furniture finishing: Chemically stain in the wood finishing.

Wednesday, February 2, 2011

Chemically stain in the wood finishing.


Chemical staining that is also called mordanting is coloring the wood by application a chemical solution on the wood surface. The coloring occurs because of a chemical reaction between the wood with the chemical. Tannin a chemical ingredient in the wood will react with certain chemicals and establish certain colors. The color change is highly dependent on the intensity of the reaction that occurs in the wood. Due to the different tannin content in the wood, the color results obtained can vary depend on the wood type. The resulting color is also depending on the chemical used.
For example, mahogany wood that contains high concentrate of tannin will turn reddish brown when react with potassium bisulfate. However, this chemical application will not produce a big color change on mahogany sap wood that does not contain much tannin. These chemicals will also produce different color changes when it applied on other type wood. This may be give advantages in the wood finishing. The chemically stain can be exploited to produce a color contrast on a veneer inlay or slice wood inlay with various kinds of on a panel. Every  type of wood will react differently and result different color with the chemical application. And a contrasting color which is very difficult to be made by stain application can obtained.
There are many chemicals that can be used to coloring the wood, and they will result different color. Ferrous sulfate (iron sulfate or copperas) will change the wood color to a light weathered gray. Sodium carbonate will form the wood color to yellowish brown to duplicating the brown photo-oxidation patina caused by sun and water exposure. Hydrochloric acid produces dark stain. There are many other chemicals that could produce a different coloration. The more information about the chemical to staining the wood can be viewed by go to this link: chemical dyes and mordants
The coloration produced by the chemical reaction will produce different  looked and effect with staining obtained by stain application. The resulting color will be more natural and durable. After the chemical staining, the finishing process can be continued with the application of other finishing materials such as: stain, sealer or top coat or even glaze to produce the desired appearance.
However, staining
chemically is relatively difficult process and should be done carefully since the chemical are mostly harmful material. The chemical staining is also very difficult to to be controlled in the result.

Here are the things that must be considered
in the chemical coloring
  • The process should be done with extreme caution.
Chemicals used for staining this wood are the chemicals that can react with wood. Mostly they are hazardous materials, therefore this process should be done carefully. These chemicals can result injury or irritation when they contact to the skin or human body. This material also interfere the respiration health if inhaled through breathing.
We have to wear the body protective such as: gloves, goggles and respirators when we applying the material. The chemical coloring process should also be done in a open place or a room with good air circulation.
Chemicals applied
by rag or brushed to the surface evenly and then wait until the reaction is complete. The time required can vary depending on the type of chemicals used. Spray gun is not recommended to be used in this process. Spray process will generate lot of dust spray and excessive waste material that would endanger the environment. The chemicals can also react with the spray gun to corrode and damage the spray gun quickly.
  • The resulting color is varying and unpredictable.
Color changes that occur will greatly depend on the chemical and the content of tannins and other chemicals in the wood. We may can control the chemical solution, but the wood may contain chemicals will vary from place to place. Therefore, the color results can be varied and hard to be controlled. The staining on  panels with a large size, the color obtained can be uneven.
  •  Color choice is relatively limited.
Staining produced by chemicals of course has limited color choices. Although there are many chemicals can be used but it still cannot produce many color as the stain. The stain coloration with many pigment and dye can almost make any color. But the chemicals stained is very limited. Only few color with some wood type are available with this method.


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