A solution to MDF expansion on joints, translams etc.

[sploo]

That could be good... or bad. Being thin is great - as it'll soak up and seal the MDF well. However, my experiences point to the need for something that leaves a fairly thick layer on the MDF, thus allowing the material to move slightly, but without showing on the final paint layer.

That said, the Rustins may do it. Unfortunately, you're not going to know for a few weeks, as you'll need to let the paint coat cure, then leave it to see what happens. It usually took at least a fortnight before problems started showing on the blocks I was testing.

 

[needmorstuff]

I hope it's ok as it's a gift.. but he won't be critical as I am not a master craftsmen by any stretch.

another thing that may go against me is I have no idea or control over the environment it is beign left in for the next week.. any way - fingers crossed.

 

[sploo]

Hi needmorstuff,

Just wondering if you've had any progress on this?

 

[needmorstuff]

yes - I did not prep it well enough so the joints do show. The rustins stuff worked well on the surface but not great on the bare mdf. The 2k paint is kind of pitted. Still I am happy with the overall result

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[sploo]

Yea, I can see the join lines in the first image - it's the same problem I've had. Imagine what it's like when making things from laminated sheets of MDF - you get a join line on every sheet!

BTW To show the pics in full size you need to remove ".th" from the URLs.

 

[Jimmy154]

Hi Vikash,

In my experience, "speed" of application doesn't have much to do with this.
With dissimilar substrates, the long-term 'sinkage' with paints will vary according to the substrate, no matter what.

MDF end grain is very much different here than the highly 'compressed' surface of MDF, as another poster has pointed out.

Even if one thinks one has overcome this problem (by whatever means) in my experience, and in the fullness of time, the paint will 'sink' differently, and, regrettably, you will see the joins.

I have been doing this kind of thing for many years, and whatever finish is used (I started with cellulose over 50yrs ago, then synthetics, then 2 pack etc., and latterly polyurethanes, acrylics, plastic coatings and whatever) and given sufficient time, you will always see the difference in 'sinking'.

Unfortunately, it seems to be a fact of life and needs to be taken into account when deciding on what finish to apply.

Yep, literally right before I got to this post I quoted I realized I already knew, what was written in the post, mainly that there is no way to prevent expansion a 100%. I have seen the graphs years ago. A change in wood water percentage will always be there. Meaning it will always expand and contract to some degree. The best realistic moisture barrier I know of given the thickness is aluminum paint. Using a plywood may be better as suggested by the giggity guy. I won't write any more on this subject, since I'm just repeating what has already been written.