A Smooth Finish

No sealer or primer With sealer and primer

It's always a good idea to put a finish on MDF projects. Sometimes this is nothing more than a coat of wiping varnish to protect against grime and moisture. But for some projects, like the drum sander, I prefer the extra durability of paint.

The smooth, flat surfaces of MDF make it ideal for spraying on paint. You won't need to do much in the way of surface preparation to get good results. But the more porous edges are a different story.

Just like glue, the edges of MDF readily absorb paint. What you can end up with is a noticeable contrast between the smooth faces and rough edges (top left photo).

To solve this problem, I take a couple of simple steps. First, I seal all the exposed edges with drywall joint compound (lower left photo). It looks like a mess, but it actually goes on easily with a putty knife or even your finger. And when dry, the excess sands off with a minimum of effort.

Then, before applying the topcoat, I seal everything with a coat of primer (lower right photo). The topcoat will then build quickly to a smooth durable, film (top right photo).

Edge sealer Prime and paint

Good woodworking,

Phil Huber
Online Editor, ShopNotes

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Printer-Friendly Version A Smooth Finish It's always a good idea to put a finish on MDF projects. Sometimes this is nothing more than a coat of wiping varnish to protect against grime and moisture. But for some projects, like the drum sander, I prefer the extra durability of paint. The smooth, flat surfaces of MDF make it ideal for spraying on paint. You won't need to do much in the way of surface preparation to get good results. But the more porous edges are a different story. Just like glue, the edges of MDF readily absorb paint. What you can end up with is a noticeable contrast between the smooth faces and rough edges (top left photo). To solve this problem, I take a couple of simple steps. First, I seal all the exposed edges with drywall joint compound (lower left photo). It looks like a mess, but it actually goes on easily with a putty knife or even your finger. And when dry, the excess sands off with a minimum of effort. Then, before applying the topcoat, I seal everything with a coat of primer (lower right photo). The topcoat will then build quickly to a smooth durable, film (top right photo). Good woodworking, Phil Huber Online Editor, ShopNotes Send for a preview issue of ShopNotes magazine More Tips & Techniques Index of Tips by E-mail More Tips & Techniques WoodNET, Woodworking on the Web Subscriber Links Update your Email Preferences Subscribe
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