Working with MDF

S7910

I'm working on a new build using an MDF flat pack from PE. Since I normally use plywood, I'm wondering what additional steps - if any - need to be taken before painting or veneering MDF. I vaguely remember reading something on PETT waaayyy back in the day about sealing MDF with glue, but don't remember if it was for a special circumstance or a general best practice and have been unable to relocate the thread.

If anyone can help out it'd be greatly appreciated.

hifiside

If your going to veneer it no sealer of any sort should be used. I do recommend using red titebond and a iron to put on the veneer. As far as painting MDF if your going to use cheaper grades of paint then use a sanding sealer so paint won’t soak in as much. My .02

jhollander

For veneer work I seal MDF with glue for iron-on and vacuum bag.  I'm using yellow glue for veneer with paper backed.  For painting I use Bin 3 shellac based and spray.  I've sealed some of the inside of Synergy horn and it seems to have helped with joint movement.

Wolf

I've long been a proponent of sealing with straight undiluted Elmer's white glue. Just use a brush and coat it. If you want Duratex, then don't bother. If you want paint, then I highly recommend sealing it at least somehow.

S7910

Thanks for the responses guys.

Based on the general consensus, I'll seal before painting. Hopefully the weather cooperates long enough to get these done before Iowa.

S7910

Before Iowa obviously didn't happen.

I wound up experimenting with a non-traditional method. Early results are promising with the first paint session today. I'm going to wait a few days and if nothing untoward has happened to the cabinet I'll post up what I used and the reasoning for it as well as some pictures.

Gowa

https://www.thesprucecrafts.com/avoid-extra-sanding-prime-mdf-2365111

http://btdwoodpowdercoating.com/

S7910

Well, I'm going to consider the Dullcote experiment a success. I wound up choosing this method through a multi-disciplinary logic train and am pleased with the results so far.

I started out with the knowledge from model building that dullcote will seal cardboard so it can be painted without deforming. Through a conversation with a fellow model builder who practiced his craft professionally in his younger years I learned that MDF is a type of cardboard. This lead to an "I wonder if ..." moment and I decided to test it out to verify the hypothesis.

This is the baffle sealed with glue (with an overspray of Dullcote because of slightly uneven coverage).

Probably could have used a little sanding and another coat of paint after, but otherwise not too bad.

Here's a side panel sealed with Dullcote only.

Other than needing to go a little heavier on the edges, I'll buy that. Nice and buttery smooth - no sanding required.

After this experiment, Dullcote is my go-to sealer when working with MDF.