Sanding sealer is a base coat that seals wood pores before painting. Projects can be finished faster and with less effort because fewer coats of paint are required. Use sanding sealer when painting or coating cabinets, furniture, doors, and more.
Sanding sealer improves the condition of subsequent coats of paint or clear finish by sealing the wood pores. With this, the coating can spread out and cover the surface rather than being quickly soaked up in localized areas.
Learn how to use sanding sealer, sanding sealer's best applications, and where to avoid using it.
Is sanding sealer also polyurethane?
Sanding sealer is like polyurethane coating but with one difference: zinc stearate additive. Zinc stearate helps the sealer produce a higher build, giving you more material to sand. Plus, it acts as a lubricant to reduce drag when sanding.
When to Use Sanding Sealer
- Painting medium-density fiberboard (MDF)
- Painting OSB
- Sealing wood knots
- Applying to furniture and cabinets
- Flattening out raised wood grain
- Painting any species of wood
- Sealing pores for smoother finishes
- Coating bare hardwood floors before topping with oil or polyurethane
Where to Avoid Using Sanding Sealer
Applying sanding sealer to a stained surface is generally not recommended, as the sanding step will scuff away the stain.
Do not use sanding sealer at a top coat. Avoid applying sanding sealer to linoleum, vinyl or glazed tiles, glass, and any type of metal.
Safety Considerations
Sanding sealer is a toxic substance and should be handled with care. Use sanding sealer only in well-ventilated areas. Methoxymethylethoxy propanol is toxic and can be absorbed through the skin, so wear latex gloves and protective clothing.
Since the point of using sanding sealer is to create dust, wear breathing protection. Sanding sealer creates fine, airborne dust that can irritate breathing passages.
What You'll Need
Equipment / Tools
- Hand sander or oscillating sander
- Paint brush
- Stirring stick
- Shop vacuum
Materials
- Water-based sanding sealer
- Sandpaper
- Tack cloth
- Microfiber rags
- Latex or nitrile gloves
Instructions
Sanding sealer should be used after the wood has been sanded down to a bare finish but before the topcoat (such as paint) has been applied.
Sand the Wood
With a hand sander or oscillating sander, sand down the wood to a bare surface before using the sanding sealer.
Tip
While sanding sealer will help smooth down the surface, you should get the bare wood as smooth as possible to start with.
Clean the Wood
First, use a shop vacuum, then clean off the remainder of the wood dust with a tack cloth or with rags.
Mix the Sanding Sealer
Gently mix the sanding sealer with a stirring stick. Do not shake the can, as this creates bubbles that hamper smooth application.
Tip
Water-based sanding sealer will raise the wood grain. If you'd like to minimize this effect, switch to oil-based sanding sealer.
Apply the Sanding Sealer
Dip the paint brush in the sanding sealer. Completely cover the wood surface with a thin coat of the sanding sealer. Do not apply a second coat at this time.
Tip
Water-based sanding sealer looks white and milky when first applied to the wood. It will eventually become clear.
Sand Down the Sanding Sealer
After letting the sanding sealer dry for at least an hour, sand it with #320 fine-grit sandpaper. Clean up water-based sanding sealer with warm water, mild soap, and rags.
Clean the Surface
Clean off the sanding sealer dust with the shop vacuum and the tack cloth or clean rags. Instead of a tack cloth, you can use a rag dampened with mineral spirits.
Apply the Topcoat
You can immediately paint or clear-coat the surface after cleaning off the sanding sealer dust.
Tips for Using Sanding Sealer
- When sanding down the sanding sealer, be gentle. The aim is to sand down the product smoothly, but not to sand through to bare wood.
- If you do happen to sand through the sealer, repeat the process. Clean the wood, apply a second coat, and sand again.
- Do not apply stain to the top of the sanding sealer. To work properly, wood stain needs to soak into the pores of the wood. Sanding sealer negates this process. The stain will sit on the surface and not be absorbed.
- Test the sanding sealer in an inconspicuous area before brushing it on.
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