Wood filler for MDF

[stevemar2]

What brand would you recommend and what shade would you suggest?
I'm completing a project using MDF and would like to finish it using only polyurethane. Is there any wood filler that would hide gaps without showing noticeably through the poly finish?

 

[Sparky617]

Nail holes or gaps in joints? For nail holes I might use saw dust mixed with wood glue into a stiff paste. For gaps in joints I'm not sure anything would fill it without being noticeable. MDF is really designed to be painted not polyurethaned.

 

[bud16415]

I don’t know about clear finishes and agree with it will be really hard to hide.



When we build speakers from MDF I found auto filler (bondo) thinned with fiberglass resin and of course the hardener works amazing and can be sanded to show no joints at all. It can even be skim coated and sanded.



Most people don’t know that bondo is just thickened fiberglass resin.

 

[James Madison]

You can 3d print the filler with wood filament

 

[zepper]

Nail holes or gaps in joints? For nail holes I might use saw dust mixed with wood glue into a stiff paste. For gaps in joints I'm not sure anything would fill it without being noticeable. MDF is really designed to be painted not polyurethaned.

That's exactly what I'd suggest. Saw dust mixed with white glue (which dries clear, vs. the yellow of carpenter-type wood glues) is the closest-looking fill you can get, because that's basically what MDF is!