Cracking of the paint film means that the paint film is cracked due to various reasons, and the causes may be as follows:
01 One-time painting is too thick
One-time brushing is too thick, which directly causes the outside to dry, and the surface is blown by the wind, which dries quickly. If the surface dries too fast, it will easily cause the surface layer of the paint film to shrink too quickly, and the surface layer will shrink easily when it dries.
02 Artificial cracking of the topcoat
Strictly speaking, the wooden substrate itself cracked due to improper construction. Problems are common in furniture assembly, such as sticking solid wood to plywood. On both sides, it is okay to say that the problem is the frame part. The standard method of sticking wood strips at this position is to first apply white glue and then use an air gun to shoot. After drying, there is no problem.
However, there are individual workers who are lazy and do not use white glue to deal with the frame part, or just hit a few places symbolically. The wooden strips of the frame part and the plywood are equivalent to be alive, and they will definitely crack after a long time. It is a typical crack caused by laziness.
03High moisture content of substrate
Cracking caused by excessively high moisture content of the substrate is generally due to cracking caused by the transition of the moisture content of the wood substrate from high to low. This kind of problem is common when the wood in the south (the moisture content is generally 20%) is pulled to the north. Because the dry matter in the north is dry, the moisture content of the wood will be reduced to zero in a short time, and it will crack when it is dry. And it's not very easy to remedy. If wood construction is used, the best moisture content is between 8% and 12%. It is not too wet or too dry.
04The temperature difference between day and night is too large
When the temperature is high, the paint film dries quickly, and when the temperature is low, the paint film dries slowly.
When the temperature difference is large and the paint film is tempered by cold and hot, the paint film will pick up and dry, and demonstrate in a cracking manner.
05Poor paint quality
The quality of the lacquer is not good and lacks stretchability. If you choose some large-scale water-based wood paint, the general problem will not be too big.
06 Improper repair of putty used by woodworkers
Carpenters cut corners to save time and use putty to scrape the wall putty to fill the joints of the wood directly with water. Although the putty can be filled flat, it has no stretchability and lays hidden dangers for cracking.
If you want to fill in the seam, the regular construction process is to choose the two-component seam king. The seam king has two functions, one is filling and the other is bonding, and it has a certain elasticity. Therefore, if there are holes in the surface of the wooden substrate, ordinary putty can be mixed with a little sealing agent, and the seam king not only easily copes with the seam, plays a bonding role, but also fills the holes.
07 The temperature is too low and the humidity is too high
If the temperature is too low and the humidity is too high, it will directly cause the paint to be unable to form a film. Once the film formability of the paint film is poor, cracking is inevitable.
08 MDF did not do a good sealant
Why doesn't a good sealant cause cracking? Because the process of MDF is formed by pressing, it is very absorbent. Get some water on the density board, it will be sucked in directly, and it will swell when it absorbs water. If the white primer is sprayed directly on the MDF, the MDF will directly absorb the water in the white primer, and the water in the white primer is used to help the paint form a paint film to ensure its stretch and stretchability of.
Under normal circumstances, after the paint film is formed, this part of the water will evaporate outwards, but now the water that undertakes this part of the function is absorbed, and only some of the filling ingredients in the white primer are left on the surface of the substrate, even the emulsion Part of it will be absorbed by the MDF, and the formation of the paint film will naturally be greatly affected, so the paint film will crack. Conversely, if a layer of sealing agent is sprayed before painting, the problem can be effectively avoided, because the principle of the sealing agent is permeable film formation, which can form a barrier between the wooden substrate and the next paint.
So, how to deal with cracked paint film? It may be recommended to use 320-mesh sandpaper to remove the problematic paint film and redo it, and then perform the construction in accordance with the construction sequence of one side and two sides.