Sand Down the Sealer: Once the sanding sealer has dried for at least an hour, sand it with a fine-grit (240 grit and up). Use the shop vacuum to remove the sanding sealer dust, followed by clean rags to clean up any remaining dirt. After cleaning off the dust, you can paint or clearcoat the surface.
Sanding sealer always must be sanded down smooth after it has dried. Sanding sealer helps improve the condition of subsequent coats of paint or clear finish by sealing the wood pores. With the wood pores sealed, the coating is able to spread out and cover the surface rather than being quickly soaked up.
It's a good idea to do this fine sanding between coats anyway to remove dust nibs. But polyurethane doesn't bond so well over finishes marketed as sealers, especially over sanding sealer. This sealer is good for use under non-polyurethane varnishes because regular alkyd varnishes gum up sandpaper.
Sanding sealer gives an added layer of protection to the wood and creates a nice smooth finish. It can be used on stained or unstained wood. Staining or leaving the wood natural is your first step in finishing. The second step of the 3-step process is a sanding sealer to create a stronger, longer-lasting finish.
For "hard to stain" woods, finish sanding with 120 grit will usually accommodate the problem. For finish sanding on most furniture hardwoods (e.g., cherry and mahogany) use 180 grit or 220 grit. The use of grits up to 600 is certainly allowed but is not standard practice.
The thin viscosity makes it easy to spread and allows it to penetrate into porous woods. To start apply 1 thin coat and allow it to dry. Lightly scuff sand to remove any raised grain fibers, then apply an additional 1 to 2 coats to seal wood and provide an excellent surface that will be ready to topcoat.
(In fact, sanding sealer will hinder the bond of polyurethane, so you shouldn't use it.) Think of sanding sealer as a production tool. If you're finishing large objects such as a set of kitchen cabinets, it will speed your work. Sanding smooth will be easier before applying the topcoats of varnish or lacquer.
Expert Tips For an Extra Smooth Finish:
A sanding sealer is not the same as a wood conditioner. Whereas a wood conditioner is a pre-stain treatment that reduces blotchiness when staining, a sanding sealer is applied only to bare wood that is not going to be stained.
A Sealer is a mixture of oils and resins as well. However, it produces low viscosity as compared to varnish, which simply means that the sealer practically penetrates in to the wood to nourish and protect not only the outside but more importantly, the inside.
System Three® Marine Spar Varnish can be used over some sanding sealers but it will depend on the formulation of the sealer. Most lacquer-based sanding sealers are not recommended because the sanding aids are wax-related.
Wipe With a Clean White Cloth
Use a clean cloth to wipe the rest of the dust from the surface of your wood after using specialized equipment. This helps you pick up any extra dust particles to ensure the wood is clean and ready for stain or paint. Use a white cloth so you can see how much dust you pick up.
The main difference between an undercoat, sealer, and primer is that primers are applied to a new surface, while sealers are used as either the substitute to a primer or they are applied before the primer. An undercoat is typically used on a surface that has already been painted.
Regular readers will know that we do not recommend over-thinning the Cellulose Sanding Sealer; it's a common myth that it needs to be thinned 50/50 to work better, but as a general rule this is incorrect.
Interior Oil-Based Sanding Sealer will dry to touch in 2 to 3 hours and can be sanded after 3 hours or when sanding sealer is thoroughly dry. Using a cleaning solvent, such as paint thinner or mineral spirits, is recommended for cleanup.
Just 1 hour after application, it sands quickly and easily to a fine powder, delivering great results with minimal time and effort. This sanding sealer builds even faster than two coats of varnish and is more forgiving of application inconsistencies - even if it drips or sags, it quickly sands out.
There's a common misconception that wood must be “primed” with a special sealer before you apply a finish. The truth is that the first coat of any finish will serve as a “sealer.” However, it's important that this first coat can be sanded easily to provide a smooth surface for subsequent finish coats.
Thinning: Mix Sanding Sealer SS-501 with Lacquer Thinner at a rate of 1:1 (equal parts). Brush: Use a good quality nylon or polyester brush.
The purpose of a sanding sealer is manifold. It seals the open pores of the timber prior to the application of the next coat, meaning that more of it stays on the surface and less of the finish is needed.
Apply one single coat with a brush or cloth and wait for it to dry. Not very long, an hour or so in warm conditions. Apply a coat of wax, or you can give it a second application of sanding sealer and then wax it.
The Golden Rule of Sanding
The golden rule for choosing your sequence is to never skip more than 1 grit. For example, if you start with P80, and need to finish at P240, rather than using every grit from P80 – P220, you can do P80 – P120 – P180 – P240.