Painting Doors With MDF Panel


From original questioner:

when painting doors is there a preference in a one piece mdf door or poplar five piece door with a mdf panel in center. does one hold up better than the other.

From contributor Le

Maple with an MDF panel will hold up better.

1 pc MDF won't have issues with the panel moving around, but it'll damage easier then a wood framed door.

From contributor Da

I have seen only a few five piece door jobs painted the thing I noticed was the glue line did show through after six months.
I have installed about 50 kitchens with 1 piece MDF doors in the last 3 years and I will say they look great but do not hold up to the fact that people don't take care with them and they look bad within months of installation from chips and moisture ingress

From contributor Le

If you make your doors correctly then you won't see the glue line in a few months. You need to account for the water in the glue. It takes about 3 days for the water in the glue to migrate out of the wood. After that you can do your final sanding and expect to not see the glue line to show up down the road.

If you are buying your doors it's a good chance they aren't putting glue on the shoulders of the door, just the stub tenon. Plus most don't clamp their doors until the glue dries. Usually clamped long enough to shoot a couple of nails in the rear to hold them together. This produces a joint that isn't tight and leaves a glueline that is greater then .002", which is the max for a good yellow glue joint.

I make my own doors and they get glued in clamps for a minimum of 45 minutes. Then they are sanded with 120 grit and if they are painted I put a small amount of putty on the joint whether it needs it or not. Lacquers have poor bridging abilities and will find any type of gap, even if it doesn't look like one. Then I will build the cabinet(s). By the time I come back to do the final sanding (150 grit) a few days have passed and the moisture from the glue has migrated out of the wood and won't pose a problem after sanding.

From contributor La

Leo pretty much has it. Especially the putting glue on the shoulders and not pinning. Dry time Also! A really good fit. If you are using brazed tooling every sharpening makes for a worse fit.

From contributor Mi

I don't like the looks of a solid mdf door, the five piece looks much better. I just like the look of the square corners much better. Glueing the tenon and the profile both should be a no brainier. I clamp mine together and brad the back and take them out of the clamps. I wouldn't send a door out that wasn't pinned, I've seen glue joints fail that wasn't pinned.

From contributor Ad

Leo's spot on.

If you buy doors from a door/drawer shop. They do not put enough glue on the doors. Why...they don't want to clean up the mess. Little bit of glue to say they did it and pinned with 18 gauge brads so it will not fall apart. However the paint always cracks.

We more or less follow Leo's protocol; however, we probably sand them after 1 1/2 days. We have plenty of clamps and keep them in the clamps for 15 minutes and pin them with 22 gauge pins. The 15 minutes is enough time for the glue to grab.

From contributor Je

Add one more in agreement with Leo. I've done a ton of painted 5 piece doors and 12 years later still no lines. I also re-finished a set of doors for a client which were purchased from one of the box stores. Couldn't sand enough to get the lines out of those! Poorly made doors can't be fixed by paint. Well made ones look great with it.

good luck,

From contributor Le

I had to refinish some bought doors and after I stripped the paint away I was able to use 2P-10 in the joint to lock it up. It worked very well and the paint flowed right over it and left a smooth surface.

I don't think this would work with a stained door, but it did for painted.