Spray Stain in the Wood Furniture Finishing

Stain is a finishing material that is used to make the color of the finishing. Failure in the stain application will affect the resulting color of the finishing. The uneven stain will produce an uneven color, while the wrong stain will make the wrong color. In the modern finishing industry, most of the stain is applied by spray. With the right technique, the application stain by spray will produce the best coloring results. The spray application will give an even color stain with high speed and high flexibility adjustment. By spraying, you can control the thickness of the stain layer. Nevertheless, the proper technique and good preparation are needed to produce good results.

spray stain

The things that must be considered in spraying stain.

• The sanding at the unfinished wood.

Sanding the wood is an important factor that will greatly affect the staining result. The purpose of sanding is to produce a clean, even, and smooth wood surface. The sanding process should be started with the coarse grade followed by finer grade sandpaper until a smooth surface is obtained. The final sanding for the unfinished wood should end up with 180 or 240 grade sandpaper. The sanding with coarser-grade sandpaper will leave scratch marks that will appear in the finished look. While the sanding with finer grade is also not recommended since it will tend to polish the wood surface and produce a too smooth but uneven surface that would interfere with the absorption of stains. Too smooth sandpaper sanding will make the wood too slick and make the stain not well absorbed by the wood. Finally, the uneven coloration or blotchy stain resulted.
The stain absorption by the wood will be highly affected by the porosity of the wood surface, since that needs to make the wood surface have uniform porosity. The porosity problem rarely happens at hardwoods such as oak, mahogany, teak, etc.  With the proper sanding process, a uniform, even, smooth wood surface will easily be obtained. But for some soft woods, such as sengon, maple, or pine, porosity could be a problem, and more intention should be done at the sanding process. You may need to do "glue sizing" to produce the even and smooth wood surface.

More about wood sanding can be viewed in our previous article: how to sand the wood  furniture

• The basic color of the wood

In wood finish, the final color is always determined by two things: the color of the stain and the color of the wood base. The final finishing color is the combination of the wood base color and the color of the stain layered on. The color of wood already exists and cannot be changed. The stain color is the adjustable tool to produce the desired color finishing. To get the required color, then you have to find the right stain color to obtain the final color. The proper stain color is the key to getting the right finishing color. To find the right stain color, you can use the "color wheel diagram."
But usually the wood for the furniture product has an uneven base color. Wood is a natural substrate from the live creature; its character highly depends on how the condition was when he was alive. The most common problem with the wood is the color base variation. Its color may vary from the sap wood to the heartwood, or there may be some red part or blue stain partly at the wood surface. The uneven wood base color will result in the uneven color of the finishing. To overcome this problem, you need to do some treatment to the wood. If the variation is not too contrasty, you can adjust the wood base color with sap stains and equalizer stains. The wood with a light color is darkened with sap stain, whereas some small disturbing colors, such as a light red or blue stain, are covered with equalizer stain. The adjustment wood base color with sap stain equalizer stain works when the color variation is not too contrasty. If the difference is too much contrast, then you may need to bleach the wood to get the even color.
See our previous article:  how to match color in the wood finishing

• Preparation of stain.

The right stain color is essential. Make sure you use the correct stain color to match the final finishing color. You can use the triangular color diagram theory to find the right stain color. Check the physical properties of the wood stain and make sure it is in good condition.
If there is any slurry, then you need to stir the stain to let all the pigments in it perfectly is mixed. View and check the appearance of the stain; make sure that the stain is in the uniform liquid mixture. If there is dirt or sediment, then it should be filtered.

• The spray equipment

The proper spray equipment is needed to get the optimum result. There are many types of spray guns, and not every type is suitable to spray the stain. The air spray gun is the most appropriate equipment for the stain application. The air spray gun can produce stain layering with the perfect atomization and has the most flexibility at the adjustment. The HVLP spray gun can also be used; it can produce good atomization stain with higher efficiency, but it has a lower flexibility. The airless is not recommended to spray stain; the L.V.L.P. spray gun could be okay, but the best choice is the air spray gun.
Make sure that the equipment functions properly.  Choose the nozzle size that suits your needs. Nozzle size varies from each brand, but essentially you need to choose the nozzle size that is big enough to produce a sufficient spray width according to the product.

• Spray techniques

The stain should coat the wood evenly. To do that, you need a proper spray technique. A skilled operator is needed to do the proper spraying technique. Set the spray gun correctly; the volume of material, the air pressure, and the width of spray should be adjusted according to the wood surface. Make sure that a perfect material atomization is obtained. 
Then the correct movement of the spray gun is needed to get the even and wet spray coat of the stain. The spray technique should also be conducted with due regard to the form of the furniture product. The complicated form product, such as chair, leg, and carved form product, is quite difficult to be sprayed, but the form will hide some imperfect staining. While the flat panels let the spray gun be moved more freely, if there is some unevenness at the stain layering, then it will obviously appear. 
To see more about spraying technique, you can go to this link: How to use spray gun correctly 1 and : how to use spray gun 2

• Layering with clear coating 

The wood stain layer is always followed by clear coating application. Some layer of sealer and top coat is needed to protect the stain and produce the smooth finish. Before it is coated with a clear coating, the stain is still very easily wiped off. The removal of the stain that has been coated with a clear coating will be more difficult. Since that, it is better to check the stain before it is layered with a clear coating. Check the staining result; make sure the stain is even with the right color before applying a clear coat to it.
For small color problems, you can remove the stain with steel wool or sandpaper. If the problem is too big, then you may need to wash the stain layer with  thinner to clean up the whole surface.
If the staining is properly done and the even stain layer with the right color is obtained, then you can continue the process with the clear coating application. 
Make sure that the stain is dry before layered with a clear coating. Usually the wood stain is a thin material that will be dry within a few minutes. But there could be some special stains that require longer drying time. Read the specification of the stain and make sure that you follow the stain specification.