Again about the "innocence" of finishing materials

When furniture is finalized, defects are identified which are often blamed on the finishing materials used or their application. This is not the first time I have written about factors influencing the quality of the finish. Read more about the influence of environmental factors here. This time I want to draw your attention to some defects that appear long before the wood is colored and varnished and go unnoticed until the finishing.

Defects from mechanical woodworking

Defects can appear as early as the cutting, machining, assembly and blank preparation stages, but go unnoticed until they are highlighted by color, primer or varnish. And if the lacquer applied is high gloss, any defect, however small, is magnified.

Let's take the example of veneer flow. This is done with knives. If the knives are not sharp enough, fiber pull-outs occur, which later lead to glue penetration during veneering. In this area, stains will appear when the veneer is tacked and adhesion to the substrate will decrease. This is why, in addition to constant knife checks, the veneers must be sorted according to quality.

The quality of the knives and changing them when problems arise or when recommended by the supplier also applies to sawing timber. They should also be chosen according to the operation being performed. Defective or unsuitable knives will result in defective cutters that will cause problems later.

Assembly of wooden elements

After making the parts, the next stage in production is assembly. This is where easily overlooked defects can occur. Adhesive stains, small dents from tools (especially in less hard woods), fine scratches, caulking with materials incompatible with the finishing products, greasy hand marks, etc. may not seem so important during assembly, but they are important in the finishing.

Sanding wood before finishing

Assembly faults can be rectified when white grinding. This is the key to a quality finish. Careful sanding will remove fine, superficial scratches. Sanding can also remove traces of glue, excess putty or handling stains.

Unfortunately, this is also where new defects can occur. Sanding with too fine-grained paper can compromise coloring. When sanding perpendicularly between elements, if the sanding is not done along the grain on both elements, the one sanded perpendicular to the grain will show scratches when staining.

Defects occurring during assembly of finished elements

Sometimes defects can appear during the final inspection, even if everything looked fine after finishing. There are cases where the furniture is not assembled before, but after the parts have been finished. If they have not been left to dry for the recommended time, impressions and scratches may appear on the varnish film from the tools used for assembly.

In general, for products with normal drying, a time of 24 hours before assembly and packaging is recommended. During this time, the film formation process is finalized and the film hardens not only superficially but also in depth. Time is also needed to remove the solvent that remains in the film. If it is not completely removed, and the furniture is wrapped in plastic film, the removed solvent may soften the film again and prints may appear on the film.

My advice is to check the wood carefully before finishing. Discovering these little "accidents" before you start staining and varnishing will save you extra work and wasted money. Because the finish will make the little "accidents" big enough to matter where it hurts - money.