" " wisno wood furniture finishing: Brushing the varnish in the wood finishing

Wednesday, November 24, 2010

Brushing the varnish in the wood finishing

The varnish as finishing materials is already well known. The varnish  as a clear coating can be applied by brushed. It makes the varnish is more flexible, it can be applied in a condition where there is no facility for spray application. But however, although the brush application is considered a simple process, it has to be done with the correct procedure to obtain good results. To master the skill of brushing the varnish, we need do lot of exercising and practicing.
 
Following are the things to be considered in the varnish application by brush.
 
The preparations.

  •  Preparation of materials.
Prepare the varnish as well as possible, choose a type of varnish that best suits to the finishing requirement. Now there are currently available varieties of varnish, each has advantages and disadvantages. Each type of varnish has different specifications and we have to choose the proper varnish according to the quality and requirement of the finishing layer. Consult with varnish suppliers about the specifications that we want so we can obtain the proper varnish.
Always check the condition of varnish before use. Read technical data; the expired date, the mixing method, the viscosity, drying time, and other technical data. Do a good stirring, and thin it with mineral spirit or turpentine if necessary.

  •  Preparation of the tools.
The brush is the main tool we need. This time there are also available brush in a variety of types and sizes. Choose a brush that is best suited for the application of the varnish. The lacquer or paint brush, a brush type with the flat and thick tip is the suitable brush for varnish application.
Make sure the brush is used in good condition and has the size matches with the surfaces that will be varnished. The brush that is too wide or too small will make the varnish application becomes more difficult.

  •  Check the condition of the environment.
An environmental condition is one factor that will affect the coating result. The ideal condition for the application of varnish is at a temperature between 70-80 degrees Fahrenheit. Varnish can be applied in the higher temperature but the temperature that is too hot it may cause some problem. Too low temperature will make the drying varnish will be slower.
The humidity is also the environmental factor that must be considered. Too high humidity will make the evaporation becomes slower happened, while the low humidity will make the varnish drying faster. The extreme conditions sometimes cause problems in the application varnish. We may need to adjust the varnish by adding some more solvent of additive to adjust with the environment condition. If it happens then we need to discuss with the varnish supplier to find the best adjustment.
To obtain good results then varnish applications also require a clean environment and free of dust room. The existence of dust and dirt in the air will stick to the wet varnish and produce a rough or dirty surface.
Although it must be free of dust, but the room for the varnish application should not be fully closed. The drying process of varnish always needs good air circulation. The drying is the release of varnish solvents into the air environment. The air that is already saturated with the solvent vapor cannot receive solvent vapor anymore so it need to be flowed and replaced with new fresh air.
  •  Preparation of the unfinished goods.
A proper checking should be done to the unfinished good accordance with the desired quality. Is the shape and size are correct? Are the doors and drawers already fit? Are the  leg are already flat? Etc.
Check also the sanding, make sure the surface has sanded and well prepared. Make sure that the surface is already clean, even and smooth. Do touch ups such as filling with putty or wood insertion in the dent, gap or crack.

 
Brushing the varnish.

 
After all the preparation is well done, then we can begin to do the process of brushing the varnish.

Dip the tip of a brush on varnish mixture. Brush must be dip until the whole tip is wet and load  enough amount of varnish. The load of varnish need be able to produce the wet and average coat. But the dipping a brush also can not be too deep because of too much varnish on the brush will cause the varnish to flow and drip.
Then brush the varnish to the surface evenly. First time stroke the wet brush in direction along the grain to the whole surface, and then follow with brushing in opposite direction (stroke the brush across the grain direction). Then use a dry brush to smooth the wet varnish with the brush stroke along with the wood grain direction.
Wait until the varnish coating is dry. Usually it takes 1 hour to 2 hours. The drying time of the varnish may vary depends on the type of varnish and environmental conditions.
The first application of varnish usually produces a film layer with uneven thickness and rough surface. This is very normal since the wood surface usually has variety porosity. The more porous surface will absorb more varnish and leave thinner film. Rough surface is due to the raising up and harden of the wood fiber with dry varnish.
Several coat of varnish is required to obtain a smooth and even film. Sand the dry varnish with #360 or #280 grade sandpaper to cut the stiff wood fibers and get the smooth surface. Then re apply the varnish with the same method as the first application.
Two or 3 times varnish applications is usually needed to produce a smooth and even surface, but it also depend on the quality of varnish and the porosity of the wood surface.



 

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