Any finish that forms on wood can be used as a sealer. Hence, some coatings are so good in this task by themselves, that they are called "self-sealing" finishes. Other finishes are not, and benefit from special sealants.

Consequently, shellac and oil-based finishes work so well on their own, that they don't require any special sealant under them. Some finishers prefer to dilute the first layer of these materials to make them dry faster or sand more easily, but that is strictly a personal choice.

It is very important to highlight that, wood also plays an important role. With very dense woods, such as boxwood, the sealant can usually be omitted.

For this reason, spongy or absorbent woods, such as poplar and most softwoods, can benefit greatly from the sealant, especially under the lacquer. The sealant layer wraps the porous wood, preventing the first layers of lacquer from being absorbed excessively.

How to apply wood sealer

You can apply the sealer as you would with any coating, with a brush, gun or pad, but that is not always the best. After a layer, the final grain and spongy areas may still be "hungry" and not sufficiently sealed, while denser flat-grain areas are beginning to accumulate too much coating.

The more and less absorbent areas would be satiated, but the excess finish on the top would not pile up.

Although it is not always practical to immerse the pieces in a sealant bowl, you can approach that by flooding the sealant by hand and then cleaning it. I use a nylon abrasive pad as an applicator and then clean it with stationery towels while it is still wet. Wear gloves and work in small areas at a time so that the sealant does not dry before cleaning.

Clarification on sanding wood sealer

Many people assume that they should use sanding wood sealer under all finishes, that is not true.

In fact, the sealant for sanding wood with stearate is not compatible with some finishes. Fortunately, distinguishing between sanding wood sealant and simple wood sealant is quite easy. Open the can and look inside.