August 1, 2012

Butt join samples

Painting over butt joins can be a challenge. Previously I've shown some samples where I've tried different methods of achieving a seamless butt join with a paint finish over, using automotive paint. They are now complete:

This one illustrates the problem. Ply also has issues:

A cheat solution (shown in ply) is grooves:


A better solution uses fibreglass reinforced filler, with two part filler over

You can see the end grain has started to show through.

The best result was achieved with MDF:

It turns out that MDF is actually easier to work with than ply, where the entire surface must also get some attention. 


  1. Great! How long did you leave these before the faults started to show up?

    As I've previously said here, I've had great results with epoxy, and good results using polyurethane ... I'm still waiting on my most recent work to 'bed down', although it's been about 2 months, and everything still looks nice.

  2. These have probably had about 6 months or more.

  3. What was the recipe and application protocol?

  4. MDF + polyurethane glue with two part bog sanded smooth then fibreglass reinforced filler applied on top, sanded back then bog applied over the top. Primed with acrylic auto paint then black. I also did one with a big groove over the join to get more filler in - not needed. There is no seam at all. Only room for improvement would be a smoother surface by using high fill primer, there is a slight texture due to not getting the surface perfectly smooth. However, the goal was to remove the seam and it has been achieved. Now just to see how long it lasts.


All comments are moderated.