how do you smooth mdf edges

How Do You Smooth MDF Edges

Medium-density fiberboard, also known as MDF, is used to build bathroom vanities, baseboards, nightstands, kitchen cabinets, interior doors, etc. With many pieces crafted using this building component, it’s expected that this will eventually wear down. MDF become dingy and chipped over time. 

MDF is smooth, but it has porous and rough edges. So, how do you smooth MDF edges? Luckily, there are ways to achieve a smooth finish, and this article will reveal to you how to deal with the rough edges and achieve smooth edges instead.  

Smooth MDF Edges by Painting 

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MDF comprises compressed wood fibers, resin, and wax and is noted for its dense, flat, and robust features. The resin and the wax on the surface tend to protect wood fibers against moisture in water-based paint or primer. These characteristics make MDF an excellent material for built-ins and cabinets you plan to paint. 

Cut edges have exposed wood fibers that absorb moisture when water-based finishes are used. This is responsible for the bumpy texture. This is true, especially if you route into the edge, cut, and expose an even more significant surface area. 

There are different ways to deal with texture issues and get smooth edges. I read some experiences shared online on how to smooth MDF edges, but of course, everyone has their preferred method. Some ways I discovered are: 

  • Use an oil-based primer. Remember that if no water is absorbed by wood fibers, there are no elevated bumps. 
  • Cover the edge with the use of joint compound and then sand smooth before painting. We learned that some don’t prefer to do this because it requires many added steps, but this remains a viable option. 
  • Start with primer put in the piece as well as all the edges using a water-based primer. Allow the fibers to swell. 

As soon as the primer completely dries, take the sanding sponge and make sure to knock this down. This pursuit does not need a lot of effort. You only need to sand some minor bumps until you achieve a smooth and silky edge. 

If plenty of elbow grease was used when you sand and more fibers were re-exposed, there would be more bumps when you paint. It should be manageable when you perform the task before you do the second coat. 

Oftentimes, there is enough primer still covering the MDF after sanding to protect fibers against paint moisture. If MDF edge display marks, sand these off before painting since the paint will just emphasize the flaws. 

Unveiling the Step-by-Step Instructions for Painting and Making MDF Edges Smooth

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How do you smooth MDF edges? Can painting really make these edges smooth? MDF may have a smooth surface, but it has porous and rough edges. For refined and smooth edges, sanding the MDF edges down is necessary. However, it would help to sand the surface lightly to allow the paint to cling. Wipe away the dust with a clean and soft cloth afterward. 

It is highly possible to get MDF back to life. You can even construct furniture, shelves, and cabinet and then paint them, resulting in a glass-like and smooth finish. 

Before You Start 

Edges drain off paint regardless of the amount of paint you put in. With MDF’s flaky edges and porous surfaces, this might not be the perfect candidate for an excellent painting job. If the paint is directly applied to MDF, this can cause distorted and swollen surfaces. However, by initially treating MDF using conditioner, you can paint it the way you would paint other less absorbent surfaces.

Surface Sealer 

Condition the MDF with the use of a sanding sealer. This is suggested before painting. The flat and large surfaces are easier to paint than the MDF edges due to the compressed word fibers from tight bonds across the surface. This requires minimal sealing and fewer large pits encounters. Oil-based sealers also work fine; however, using water-based sealers to sand surfaces is also a considerable option. 

Edge Filler 

MDF edges can be conditioned with the same sealer used for their surface. Since edges are porous, apply multiple coats of sand and sanding sealer between every coat. It seems to be a better option to fill the edges. This is best performed using fillers based on acrylic polymer. Such filler needs one or two applications and can do well with large pits usually encountered in MDF edges. 

What Will You Need? 

How do you smooth MDF edges is an important question. What will you need to do the necessary task is another one. You can smooth MDF edges successfully if you have all the required equipment or tools at hand. You might need: 

  • Sanding rock
  • Roller 
  • Foam roller covers 
  • Tack cloth 
  • Putty knife
  • Brush 
  • Oscillating sander (this is optional) 

For the materials, you will need the following: 

  • Polymer-based filler
  • Sanding sealer
  • Paint 
  • Liners and paint tray 
  • Sandpaper 

The Step-by-Step Instructions to Smooth MDF Edges by Painting 

Painting Medium Density Fiberboard or MDF is a skill you need to have, primarily if you work and handle this building material most of the time. MDF is a versatile material used by many homes; however, you need to get the perfect finish that would suit your home. To achieve a smooth finish, MDF needs to be painted. 

Here, we unveil to you the best techniques and steps you need to follow when sanding and painting MDF  to achieve smooth and refined edges. If done correctly, you can expect excellent results every time. 

1. Sand the Surface and Edges 

With sandpaper on the sanding block, sand the surface gently. If the MDF edges are flaky and bumpy, smooth these edges carefully as well. Sanding the uncoated MDF intensely might lead to scratches, and this can make sealing and painting more difficult. The aim is to eliminate wax coating and knockdown anomalies and high spots first and then achieve a smooth surface. 

2. Apply Polishing or Sanding Sealer

Sanding sealer should be stirred to mix. Pour the product into the lined paint tray and then roll it to the surface. 

3. Sand Surface

Allow sealer to completely dry for about an hour. The sealer has probably raised the MDF surface. With grit sandpaper or an oscillating sander, you can proceed with surface sanding and make the MDF smooth. Make sure not to sand across the sealer. 

4. Clean the MDF’s Surface 

You first need to clean the MDF’s surface using a shop vacuum and a tack cloth. 

5. Apply the Second Coat Sealer and then Sand It 

At this phase, you must roll on the second coat of the sanding sealer the same way you did in the first coat. Let the second coat dry completely and sand the surface once again. Since the surface shouldn’t be raised, you must be able to switch to sandpaper with a finer grit. 

6. Apply Filler to the MDF Edges 

With a putty knife, you can begin to apply filler to the MDF edges. Press the filler deeply into the cracks and holes and let it dry for at least 2 to 3 hours. Another method to apply filler to the edges of MDF is to rub it on with your finger. This method seems messy, so you might need to carry out more sanding to eliminate ridges from the MDF. 

7. Sand and Put in Second Filler Coat 

Sand the MDF edges lightly by hand with sandpaper (preferably #220) and wipe down with a clean and dry cloth. Add the second coat of filler and allow this to dry. This time, let it dry for four hours. 

8. Final Sanding 

It would be best to sand the second coat of MDF edge filler using grit sandpaper (preferably #320). Move the latter into the MDF surface again and sand this as well. Pay close attention to the 90-degree angle between the surface and the edge. 

9. Paint the MDF 

With a clean tack cloth, wipe down the Medium-density fiberboard. Apply paint following different ways. You can brush, spray and roll. Allow for at least one hour between recoats. Recoat twice or thrice if necessary. 

Tips for Painting and Important Safety Considerations 

When you put edge filler, try rounding the edges. Bulk up the filler for about ¼ inch and then carve it to a circular contour by hand using sandpaper. Moreover, sanding polymer filler and sealer absorb paint at different rates. To balance, apply just a thin layer of quality primer into the MDF edges before you paint it. 

As much as possible, prevent the use of drywall compound as MDF edge filler. Use polymer-enhanced filler instead for more strength. Filled and sealed MDF can’t be stained, only painted. For safety considerations, make sure to work in a clean and well-ventilated place, primarily when you use coatings, fillers, and paints. Wear latex gloves. Use proper breathing protection when you sand. 

Final Thoughts 

MDF is a versatile and reasonably priced material, and it’s a perfect choice for home projects. The keys to smooth MDF edges are sanding and painting, and there are proper ways to do these to ensure excellent results. The question “how do you smooth MDF edges?” will no longer bother you since this article aimed to give you clear answers and reveal to you the instructions and techniques you need to do to achieve smooth and refined MDF edges. 



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