How to Seal MDF Before Painting (Detailed Guide + Tips)

If you buy something through our posts, we may get a small commission. Read more here.

Have you ever wondered about the makeup of most modern furniture? It’s often crafted from MDF, or Medium Density Fiberboard. However, despite its ubiquity, MDF can be quite susceptible to everyday wear and tear, especially when painted.

In this guide, I’ll share how to seal MDF before painting. This added layer of protection can make all the difference, safeguarding your furniture against potential damage and ensuring longevity for your cherished pieces!

Importance of Sealing MDF Boards

Sealing MDF boards is an essential step in finishing a project. It is both for the protection of the piece and longevity of your fiberboards:

To Extend its Service Life

Sealing MDF boards will keep them looking their best for longer, so you can be sure your furniture or project will last and stand up to wear and tear.

MDF board

To Prevent Moisture & Water Penetration

Another importance of sealing MDF boards is that they are a great way to protect your home from water damage. Water can cause wood to swell and expand, which can cause the wood to split and crack.  

Sealing Your MDF Workbench Top from Moisture: 4 Steps + Methods

Sealing MDF edges is the key to long-lasting performance. For a completely waterproof workbench top, follow these simple steps and avoid significant moisture damage.

Necessary Materials

Step #1: Prepare

For your safety and well-being when handling chemical compositions, especially during the sealing process, I strongly recommend adhering to the following precautions:

preparing work area for painting

Work from a well-ventilated area like the garage or workshop; wear gloves and long sleeves for added protection; use drop cloths to protect objects in surrounding areas as well as flooring. 

Depending on which type of sealer, you may also need to wear goggles and face masks. By following these steps, you can keep yourself safe while creating any project!

Step #2: Scuff Sand Your Workbench Top

Achieve a smooth surface perfect for painting by sanding your wooden workbench. For the best results, use medium-grit (e.g., 220) sandpaper or a block sander to control pressure and movement while avoiding grain lines in the wood product. 

Wear eye protection and a safety mask as you go to prevent dust from getting into your eyes or lungs. Keep movements light but evenly distributed across all areas of the workspace, including its edges.

Step #3: Seal the Wood Edges

When tackling projects with medium-density fiberboard, heed this advice: remember the edges! They are more rough and porous than either side and will quickly absorb liquids if left unsealed. 

sanding edges of MDF board

To keep them protected, use a sealing agent to form an impenetrable coat around these vulnerable areas – below are five common methods and products out there so you can choose what works best for you.

Method #1: Use MDF Edging Tape

Edge banding, or edging tape, can add a professional finish to any MDF project. Available in various sizes and types at different price ranges, it requires cutting into the right size strips for your edges. 

To attach them with strong adhesion onto the board edge, just iron on medium heat and use gentle pressure while moving slowly over its surface – then smooth away using a wooden block.

After the MDF panel is dry, trim away any excess sheeting or overhang with care. Then give it sand to get a smooth finish.

Method #2: Use a PVA Glue

Sealing the edges of your project is easy with PVA glue. Apply it using a synthetic brush, spreader, or spray bottle and wait to dry before lightly sanding it down. 

PVA wood glue

Be careful not to apply too much pressure when sanding – you just want to scuff up the surface slightly without removing what’s there!

Method #3: Use Drywall Compound & Primer

This two-step process gives your MDF workbench [1] an extra-durable finish! Combine drywall compound and lacquer primer to create a long-lasting coating. 

Spread the compound evenly on the edges, wiping away excess as you go for a smooth, even surface. 

Make sure to follow product directions for drying time – then scuff sand it just like previous techniques before adding the topcoat of lacquer primer. 

Applying either by brush or roller will do; however, check recommended instructions from manufacturers first. 

paint roller and drywall sealer

For a smooth finish, always sand down your edges post-priming. Also, steer clear of water-based or latex primers to sidestep potential paint complications down the road.

Method #4: Use Wood Fillers

Get a perfect finish on your MDF board by applying a thin layer of wood filler or putty. Spread an even coat over the edges with a putty knife, then let dry for a manufacturer-recommended duration before sanding to smooth everything out. 

You can also use pre-made filler in the same shade as your material for optimal results – or you can easily DIY it yourself!

Method #5: Use Oil-Based Filling Primers

An easy way to seal the edges of your painted board is with oil-based filling primer. Smooth it on using a brush or sprayer, then let dry before lightly sanding, just enough scuff to prep for painting but not so much that you remove all the product.

Step 4: Seal the Wood Surface

It’s time to give your MDF workbench top a smooth finish. Sealing both sides of the board protects it from water and moisture while helping ensure that the paint adheres correctly. 

spray painting MDF board

Before you dive into the painting process, I recommend selecting one of the following sealing techniques for peak results:

Method #1: Use an Enamel Primer

Get the perfect paint job for your MDF surface with thin layers of enamel primer. It’s practical and lets you choose a complementary shade, ensuring every color pops and stands out!

Method #2: Use a PVA Glue

Achieve a reliable and solid bond with PVA glue. This handy adhesive is available in liquid form, making it easy to apply. 

For best results, use a synthetic bristled brush or spray bottle to cover all surfaces with thin and even layers. Just be sure to saturate the material, which could cause swelling damage appropriately. 

PVA sealing MDF

If you need a different diluted solution for coating larger areas, opt for acid-neutral varieties already formulated for binding books and papers. Use these with rollers or spreaders for optimal coverage without any risk of warping your project materials!

Method #3: Use a Spray-On Lacquer

You can also achieve an optimal workbench finish with a spray lacquer! Choose between clear or tinted for unique results. 

Precisely, outdoor-designed lacquers form the most secure primer and give you a great foundation to apply paint on afterward. Follow all instructions when using this method to get professional-looking outcomes every time!

Also Read: Applying Thompson’s Water Seal Using a Sprayer 

Useful Tricks for Sealing MDF Boards

Sealing MDF is an important step when crafting, but it can be easy to make a mistake. To guide you through this process seamlessly, I’ve outlined four tried-and-true tips:

MDF board

FAQ

What is the best sealer for MDF?

The best sealer for MDF is dewaxed shellac. It is an A+ choice for protecting MDF surfaces.

Can you paint straight to MDF?

You can paint straight to MDF, but the results won’t be optimal because MDF absorbs paint quickly. You’ll use more paint than necessary, and the procedure will take longer.

Can you make MDF waterproof?

Yes, you can make MDF waterproof by applying a high-quality sealant, varnish, or stain. For extra waterproofing, add some special paint resistant to wet conditions.

Does coating MDF make it waterproof?

Yes, MDF can be moisture-resistant with the application of quality-grade products, following the right process as well as proper care and handling. However, prolonged exposure to moisture can still lead to swelling, warping, and eventual deterioration of the MDF.

How can you seal particle boards?

Ensure your particle board is airtight and waterproof by sealing it with a brush-on sealant. Paint on an even coat of clear acrylic to all edges and other spots prone to moisture damage.

Read Next: Best Redwood Sealers 

Conclusion

Learning how to seal MDF before painting can be a great way to save money on your woodworking projects. 

Sealing acts as a shield against moisture and everyday wear, ensuring that subsequent paint jobs or finishes showcase their true beauty. In addition, there are various methods you can try depending on your budget and preference.

robert headshot

Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

Leave a Reply

Your email address will not be published.

Related Articles
Join our community on facebook and get 3 woodworking plans for free!