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Interior Door Panels2/9/15
I have a client who used a competitors raised panel door where the panel is showing the glue lines after they have applied an extremely high gloss finish. I have no idea of M/C or type of glue but I do know the doors are solid Maple throughout. I suspect they may have just biscuited the panels together whereas I use a glue joint knife. They want me to fabricate a new door that has panels that will remain as a perfect base for the high gloss finish. So I am wondering if anyone has had any luck using a raised panel with solid wood edges with an MDF face ? or something similar? I would be most worried about the movement of the wood/MDF marriage. The client has suggested solid MDF panels but I don't know how you can ever sand them smooth enough for the high gloss finish ( it looks like plastic) Perhaps a solid wood panel fabricated properly is the obvious choice but want to open to others experiences. Thank you
Solid wood moves, and no two pieces the same. It could be the original panels where sanded to quickly after glue up and the joints have sunk but I suspect it is just natural movement. You don't say if they are interior or exterior but if they want high gloss sounds like veneers over a flat substrate like mdf, but that makes raising a whole other problem.
You can make the door with solid mdf panels, no problem. Prime and sand the raised portion before assembly. In my opinion making a panel with a solid wood, mitered edge is extra work for a interior paint grade door.
And, dare I say, neither a biscuit joiner or a "glue joint knife" will make the edge glue joint any better.
I agree with Geoff. Use MDF sand the profile well and prime with a heavy base primer MLC Clawlock or the like. I think you are going to continue to have problems using solid under a high gloss finish.
Rimming stable panels with solid wood that is later raised is a premium way to make raised panels. The stable core can be framed, sanded smooth, veneered, then raise like solid wood. The resulting panel is stable, and can even be lightly glued into the frame. Save the gawd-awful MDF for the core, where it belongs, and let the wood show.
I was assuming a pigmented solid color finish. If this is a clear finish I would agree with David.
Likely the panels were processed to quickly. Glued up, taken out of the clamps, sized and widebelt sanded within 2 hours.
If you don't want sunken glue joints you will need to wait 3 days after gluing before you sand them. That gives time for the water in the water based glue to evaporate out of the wood cells and have them return to their normal state.
Other options are use a non water based glue such as epoxy or polyurethane.
Sanding and priming moulded mdf edges is indeed laborious, as is rimming an mdf panel with solid wood. We have found that using Medex reduces the effort of prepping edges for paint considerably.
You can also use ultra refined mdf. You can't see the porosity after priming and sanding to 320. It costs alot less than medex.
In addition to the common reason for visible joints...sanding too soon after gluing...having the wrong MC at the time of gluing is another reason--as the wood eventually dries and shrinks, the glue joint is a bit more rigid than the wood, so it does not shrink as much. And a third reason is that the joints are inferior because there was too much time between surface prep and gluing, so that some shrinkage occurred and the surfaces were not flat enough. Finally, with some PVAs, heat from sanding or even finishing ovens can soften and melt the adhesive, causing the glue to be slightly squeezed out of the joint. The bottom line is that without examination, the cause is not clear.
On the other hand, millions of panels have been made with no problems, so using MDF, which is certainly a good idea, is not essential if the panel is made properly.