Paint Cracks in Five-Piece Doors

Some cracking is pretty much inevitable when you paint five-piece wood cabinet doors. September 25, 2014

Question (WOODWEB Member) :
I have been outsourcing my doors for about a year now. Iím having issues with cracking around the center panel on five piece doors which are made from maple. The center panel is .25" veneer covered MDF. Here's what I'm doing: First coat primer sand smooth. Caulk around perimeter (front/back) with Sherwin Williams Urenthanized elastomeric caulk. Second coat primer, sand smooth. First coat Chemcraft Aquaset pigmented white, sand smooth. Final coat Aquaset. Sprayed on 3-5 wet mils. I am caulking the seam to avoid shadow line around the perimeter where the center panel meets the cope/stick frame. How do you paint/finish outsourced doors?

Forum Responses
(Finishing Forum)
From contributor H:
I make my own doors and glue the 1/4" panel into the frame using silicone caulk. That said it is five pieces of wood all moving in a different direction at the same time, something is going to give and it will show at the joint. I think you just do the best you can.

From contributor B:
From my experience, it is almost impossible to paint five piece doors without the joints and the crack around the inside showing. I have tried caulking and still have problems with the cracks showing up. MDF routed doors are about the only solution to the problem. For painted cabinets, I will only do with a glaze finish. If the customer wants pure painted finish, I send them to someone else. Let them have the headaches.

From contributor K:
Iíve had the same problem. If the doors already have primer on them I use a wood filler by Elmerís. What I do is use the tube just like caulk (wiping the excess out with a wet rag). If the doors do not have primer on them yet, I just use caulk. It seems to be that the caulk has a hard time adhering to the primer and when the paint sprayed on top of it starts to cure/shrink, it pulls free of the primer but it doesnít happen on bare wood. Other than that you really shouldnít be putting caulk under paint anyway. You could always tint the caulk to match your paint with a Red Devil Creat-a-caulk, then apply it after the doors have dried. There will be no cracking, as the caulk is flexible and will move with the expansion/contraction of the wood.

From contributor D:
You are caulking the panel into the doors? That is a bad idea. Our shaper cutters put a very small bevel on the inside edge of the profile, so there is not a sharp edge against the panel. If you have a sharp edge against the panel it will fill with paint and crack, or you can caulk it, and still have it crack. You need to talk to your door supplier.

From contributor A:
The only way to prevent cracking on a five piece door is to use MDF panels and glue them into the stiles and rails.

From the original questioner:
Thanks for the responses. When I used to build my doors I would glue the center panel (ply or MDF only) into the rails/stiles. Then I would run a bead of caulk around the perimeter. I doubt I can get my supplier to start doing this. Believe me, I would rather not caulk at all. But the end result, even with the eased/beveled edge, is a shadow or crack that immediately appears only primer/paint get applied. There must be a way to do this without caulk. Applying caulk after the door is painted is not an option. Even if the color matched perfectly this is not good enough for kitchen cabinetry. I have asked my supplier about this and they have no advise on finishing what so ever.

How is a factory painted door completed? I know those go through a half million dollar finishing line, but those painted doors do not have caulk. Are the center panels glued in? Do they pre-finish the center panel before assembly? I used to do this to deal with expansion/contraction so that visible unfinished wood could not be seen. Those of you that are outsourcing doors and painting them please describe your process.

From contributor B:
I hate caulking but most customers want it and it does look better (though I just finished a job with beadboard panels and couldn't caulk them). I use GF pigmented poly and cheapest/basic acrylic latex caulk. A couple of things: I would look at the compatibility of your caulk with your finish. Per their tech sheet it's urethanized for max adhesion and recommends "Use only with adequate ventilation". Avoid contact with eyes and skin. Wash hands after using. Do not transfer contents to other containers for storage." To me that's a red flag for compatibility with your WB finish.

How long do you let it cure? They say it "Can be painted after 30 minutes at 75įF and 50% relative humidity. For best results, a minimum of four hours dry time is required before painting with latex or oil base paint. Allow extra dry time during periods of high humidity and/or cool temperatures." I've had caulk crack if I haven't let it dry/cure long enough.

From contributor M:
My supplier uses foam to evenly space the panel in the routed channel then they use a stapler to shoot the panel to the frame so that it does not move. MDF center panel only when doing painted. I use DAP quick dry WB caulking. It says paintable in 30 min, but this is only with latex paint. I found a minimum of four hours in good weather, overnight (12 hours) any time itís below 65 degrees. I can do it before or after the first coat of primer. I use as small of an amount as possible to help it fully cure faster.

From the original questioner:
Caulk is applied then allowed to dry overnight. Incidentally I caulk the door before applying any primer. Not in between primer coats the way I described. I have not tried stapling the panel in place. The problem on some doors would be if the profile is too thin then the staple or pin could easily shoot through the door face. It would be great to hear from someone that paints outsourced doors, especially their process and materials used.

From Gene Wengert, forum technical advisor:
From a technical point of view, when you see a crack, you know that the wood has moved (most often the wood has shrunk). Wood only moves because it moisture changes. This year especially, we have cold outside weather which means that inside our shops and also the customer's homes, the humidity is quite low for a long time. The wood responds to low RH by losing moisture and shrinking and with the shrinking comes the cracks. Unfortunately, most wood we buy today is a bit too high in MC for the dry conditions we have in the shop and in home. You can humidify your shop and the problem will be gone. However, when the customer puts these doors in their dry environment, the wood will shrink and the cracks will open. So, do not make your shop more humid than the customer's home. Also, the summer conditions are around 9% EMC in a home or shop and the wintertime is often under 6% EMC. So, even if the wood is perfect in its initial MC, there will be some movement (although slow movement taking six months, which allows the wood to give a little).

From contributor B:
I caulk the door before applying any primer. The spec sheet for your caulk states to prime the surface first before applying. We/I use Decorative Specialties doors and the problem is always going to be the shadow line regardless of who makes the doors. If you flood too much finish where the panel meets the rails/styles you're going get an uneven shadow line hence the necessity to have to caulk.

From contributor M:
I was describing outsourced doors. I use cal door. They use the method of stapling the center panel no matter what the profile. They shoot the staples at an angle into the frame to avoid blowout.