What is Sanding Sealer and How To Use It

Getting a smooth, faultless finish that lasts is the ultimate goal when refinishing hardwood floors, furniture, or cabinets. A flawless finish can increase the longevity of your woodworking projects in addition to their aesthetic appeal. Because of its pores and irregularities, raw wood can be difficult to finish because of how the finish sticks to the wood's surface.

Sanding sealer is a base coat that is used to seal wood pores before painting. It contains zinc stearate. One excellent way to get a smoother surface faster and ensure that your topcoats adhere properly for a beautiful, uniform finish is to use a sanding sealer. We'll cover what sanding sealers are, why they're used, when to use them, and how to apply them for the greatest results in this tutorial.

WHAT DOES SANDING SEALER DO (AND WHY USE IT)?

These products offer a number of advantages to all woodworkers, amateur or expert.

• FILLS IN WOOD PORES: The sealer acts almost like a little spackle, seeping into and filling the wood's natural pores. By plugging these pores, the paint or stain has a smooth, uniform surface to stick on.
• FORMS A BARRIER: This layer stops paint or stains from penetrating the wood too deeply, allowing the topcoats to settle uniformly on the surface instead of soaking in unevenly. This contributes to a more uniform color.
• ENHANCES ADHESION: Your paint or stain will adhere better, thanks to the smoother base. Fewer issues with peeling and shipping result from this.
• SANDING IS MADE EASIER: Wood sanding sealer minimizes the need for additional sanding by lowering the amount of grain rising.

WHAT CONSTITUTES SANDING SEALER - TYPES AND COMPOSITION OF SANDING SEALERS

Zinc stearate is used with a diluted resin basis (such as varnish, shellac, polyurethane, or lacquer) to create sanding sealers. This is all made possible by the soap-like substance zinc stearate.

ROLE OF ZINC STEARATES

• FILLS AND SEALS: It immediately fills the pores in the wood and builds up a thicker layer of the basic resin.
• SIMPLER SANDING: The zinc stearate powder lubricant lessens friction between the sandpaper and the wood surface. You can sand a smoother surface more easily since sandpaper moves across wood surfaces more smoothly.
• REDUCES CLOGGING: The lubricating qualities of zinc stearate help lessen the sandpaper's tendency to become clogged with wood dust and coating debris.

DIFFERENT TYPES OF SANDING SEALER

1. OIL-BASED SEALANTS FOR SANDING
   

• LACQUER-BASED: Produced using a lacquer foundation, commonly nitrocellulose lacquer, which sands easily and dries quickly. 
• POLYURETHANE-BASED: After curing, the polyurethane resin basis offers outstanding durability and water resistance. 
• VARNISH-BASED: Usually a mixture of resins such as alkyd or phenolic and drying oils such as tung oil or linseed oil. Varnish sanding sealers offer a glossy appearance and good protection.

2. WATER-BASED SANDING SEALANTS
   

• WATER-BASED: Using water-soluble resins in their formulation, they dry fast and serve as a foundation for finishes that are either water- or oil-based. Additionally, water-based sanding sealers are more environmentally friendly because they emit fewer volatile organic compounds (VOCs) and have a mildew smell.
  

3. OTHER CATEGORIES

• SHELLAC-BASED: Sanding sealers based on shellac have high adhesion and work well with a variety of finishes. Fun fact: The female lac bug secretes a resin that is used to make shellac.

WHEN TO APPLY SANDING SEALER

Although it's not usually required, sanding sealer can be very helpful for:

• WOODS: As we've already discussed, the primary function of sanding sealers is to close up wood pores efficiently. Because of this, sanding sealers are essential for open-grained timbers with more apparent pores, such as oak, mahogany, and ash. 
• PRE-STAINING: To help avoid blotchiness and provide a more uniform color distribution, a sealer must be used before staining.
• HIGH-GLOSS FINISHES: Sanding sealer can help you smooth out the surface to hide any blemishes that would diminish the finish if you're looking for a perfect mirror-like finish. 
• WOOD FURNITURE AND CABINETS: Sanding sealer produces a consistent finish and shields wood furniture and cabinets against moisture, stains, and scratches—all of which are common problems for wood furniture and cabinets. 
• HARDWOOD FLOORING: Sanding sealer protects and preserves hardwood floors while improving their appearance. It also makes upkeep simpler. For a long-lasting, professional-quality finish, use it with our best-selling floor sanding and refinishing products. 
• PAINTING MDF/OSB: Manufactured woods, like oak and mahogany, are frequently highly porous. Sanding sealer is an excellent way to give various kinds of wood a smooth coated finish.

WHEN TO AVOID USING SANDING SEALANT

It's not always necessary to use a sanding sealer. In the following situations, you may choose not to use it:

• NON-POROUS/CLOSED-GRAIN WOODS: Woods with very tight pores, such as cherry and maple, have lower absorbencies by nature. Since these wood kinds won't benefit much from the pore-filling properties, sealing the wood sealant might not be necessary. 
• RUSTIC OR DISTRESSED LOOK: Sanding sealer may work against your desired outcome if you're going for a deliberately rough surface or if you want to draw attention to the wood's inherent texture. 
• OVER ALREADY-APPLIED FINISHES: Sanding sealer is meant for unpainted, virgin wood. If applied on top of an existing finish, good adherence may be hindered.
• TEMPORARY PROJECTS: You can economize by omitting the sealer if time is of the essence and a superior finish is not necessary. 
• OIL-ONLY FINISHES: Linseed oil and tung oil are two examples of oil finishes that are intended to pierce deeply into the wood in order to protect and enhance its natural beauty. Using a sanding sealer can hinder the oil's ability to soak correctly, reducing its intended benefits. 
• OPEN-GRAIN WOODS WITH EXPOSED FINISHES: Sanding sealer may cover up too much of the texture you're attempting to highlight in projects where you want to highlight the open-pore woods' natural grain pattern, such as oak or ash.

HOW TO APPLY SANDING SEALER: STEP-BY-STEP GUIDE

ITEMS YOU'LL REQUIRE

• SANDING SEALANT: Depending on the type of wood and desired finish, select the proper sanding sealer type. 
• SAFETY EQUIPMENT: Put on safety goggles, a dust mask, and gloves, among other protective gear.
  Fine-grit sandpaper, often with a grain of 220-320 
• APPLICATOR: Make use of a sprayer, foam brush, or superior brush. 
• TACK CLOTH: Keep a fresh tack cloth on available to polish the surface and remove any leftover sealant.
• VENTILATION: If necessary, wear a mask or work in an area with good ventilation. 
• STIR STICK: To ensure that the sealer is consistent, you must stir it. 
• DROP CLOTH OR PLASTIC SHEETING: To keep your workspace spill-proof, place a drop cloth or plastic sheeting underneath it. 
• CLEANING SUPPLIES: Keep mineral spirits or the proper solvent on hand to clean your applicators or brushes after each usage. 
• NOT REQUIRED: Sanding Block: To evenly sand bigger areas, use a sanding block.

PREPARATION

• SANDING

Your outcomes will be better if the starting surface is smoother. Now that you've removed any finishes, blemishes, and irregularities from the surface by sanding, you can prepare the wood by sanding it with high-grit sandpaper.

An orbital sander fitted with a high-grit sanding disc featuring VAC holes or a portable belt sander equipped with a 220-320 grit sanding belt can greatly simplify the process while working on larger surfaces.

• CLEAN

If necessary, use a hoover to clean the surface and remove any dust and debris completely. A tack cloth works well for removing tiny particles from the surface.

APPLICATION

• STIR

For the zinc stearate to be distributed uniformly throughout the mixture, thoroughly stir the sanding sealer. 

• APPLY THE BASE COAT

Apply the sealer in a thin, even layer by following the directions on the product. Follow the grain of the wood when working.

• GIVE IT TIME TO DRY

As directed by the manufacturer, allow the initial coat to dry fully. This time will vary between manufacturers and based on the base (water-based dries fastest). 

• SAND IN BETWEEN LAYERS

To smooth out any raised grain or flaws, carefully sand the surface with fine-grit sandpaper after the first layer has completely dried. 

• APPLY ADDITIONAL COATS (IF NEEDED)

For most jobs, one coat is sufficient, but a second coat could be helpful. Go back to steps 3-5.

COMPLETE SANDING AND CLEANING

• A FINAL SANDING PASS

Do a very gentle final sanding with a fine grit (220 or higher) after the last coat dries.

• CLEAN UP

Before beginning to apply your topcoat, make sure to hover or wipe away all dust fully.

SELECTING THE FINEST SAND SEALER

• FOR STAINING: To improve stain adhesion and avoid color fading, use a dewaxed sealer. 
• PAINTING: Because water-based sealers cure quickly and have minimal volatile organic compounds (VOCs), they work best underneath water-based paints. However, because of their longevity and penetration, oil-based sealers work better underneath oil-based paints.

SAFETY MEASURES

Even though it's the final component of this guide, safety comes first. When using a sanding sealer, be sure to follow these safety guidelines:

• VENTILATION: To prevent breathing in dangerous gasses, always operate in an area with good ventilation. 
• PROTECTIVE GEAR: To guard against dust and chemical exposure, put on a respirator, safety glasses, and nitrile or latex gloves. 
• CORRECT HANDLING AND DISPOSAL: Apply the seal and clean up in accordance with the manufacturer's recommendations. Sealers should be kept out of direct sunlight in a cool, dry location.