What Does Grain Raising Mean?
Grain raising refers to a coating failure that especially occurs in the coating of wood. When a water-based coating is used on the coating of wood surfaces, fibers stick up from the wood, causing a dull appearance and rough surfaces of the paint finish. This is known as grain raising.
The water in the paint or even moisture from the atmosphere makes the wood fibers swell and lifts them up. Grain raising leads to the failure of the coating, which ultimately leads to corrosion.
Corrosionpedia Explains Grain Raising
The water contained in a water-based latex paint will raise the grain. The magnitude of grain raising on wood surfaces will vary depending on the nature of the wood (for example, southern yellow pine raises more grain than other kinds of woods). It is better to switch to an oil-based paint and use a good primer to decrease the chances of grain raising.
Since water-based paints produce more grain raising than oil-based finishes, they require a different finishing procedure. For example:
- First spray the wooden object to be coated with water or rub down with a damp cloth.
- Allow some time for the wood to dry and then sand lightly to remove the raised grain (sanding is only done in the direction of the grain of the wood).
This procedure makes the wood suitable for accepting water-based finishes and decreases the chances of grain raising after applications of coatings.
Sanding not only removes raised grain from the surface but also reduces the consumption of coating materials. The quality of the surface depends on the grain size of the sanded paper or abrasive. When the grain size of the sandpaper is 180-grit instead of 120-grit, it gives a heavy grain raising. An improperly sanded wooden surface absorbs more coating materials and causes intense grain raising.