We had some large painted slab cabinet doors warp after the mirror was glued to one side. We used moisture resistant MDF as the substrate. The doors were painted on all sides and edges before the glass contractor attached the mirror. The mirror was attached using Gunther mirror mastic following Gunther's instructions. I am convinced that the warping was the cause of an unbalanced condition. I am trying to figure out a way to balance the mirror with something that won't double the weight of the door and allow installation of euro hinges. Any ideas?

You may want to try a heavy laminate on one side. Maybe a chem metal aluminum panel.

I would first be more inclined to go with a ply substrate over mdf. Moisture resistant won't help in this application.

If possible I would do a sample with 1'' veneer grade ply and mirror.

If you get that to cup from a mirror on the face I will be surprised.

Let us know how it goes.

I have been asking around other shops in my area. Everybody has a different idea of what when wrong and how to fix it. One other cabinetmaker suggested your solution only using a uniform laminate product (baltic birch or apple ply). I hesitate to use a substrate with more wood as this is a bathroom with a large tub. I like your idea of the heavy laminate on the back. I am limited to 1" thick doors because we are using 170 degree euro hinges. One thought was to go the other direction and use hollow core construction with a heavy laminate on the back and mirror on the front. We could use inserta style hinges. We would adhere the heavy laminate on the back with the same mirror mastic used on the mirror. Thoughts?

I forgot to mention that the mirror is 1/4" thick beveled so whatever this final solution is is limited in thickness and weight by that mirror. I think I will try a sample with the 1" as you suggest.

I had the same problem with a large closet door a couple years back. I had used 1/4" mirror w/ beveled edges glued on to mdf with adhesive from the glass shop and added a laminate backer to the back side. It warped after a couple months and I spent a lot of time trying to figure out how to force it back to straight….unsuccessfully.

In the end I re-made the whole door. I built a frame out of 4"-5" wide mahogany and then filled the centers in with a grid kind of like a torsion box construction. Glued it up and sanded it flat and then applied a laminate to one side and the mirror to the other. It came out flat and to my knowledge still is to this day. And I know this particular client will let me know if anything happened!

I uses SOSS hinges for this application though I'm sure euro hinges would work just fine with it as well. In my application the mirror had to look as if it was mounted to the wall and the application was too heavy for euro hinges. The bonus of the mahogany frame was that is was much lighter than the mdf so not as much stress on the hinges.

good luck,
JeffD

Thanks. That is the solution I came up with too. I am going to use uniform laminate birch for the frame hollowed out so that it makes a 4" frame. I will fill the hollowed out section with structural honeycomb material (Nida-Core which is used in boat building). I am glad to hear that you used laminate on the back as that was my choice but I was not sure it was a good balance to the mirror. Did you glue the laminate on with mirror mastic? I was thinking I had to use the same glue on both sides. Mirror mastic works with laminate but it will be a bit tricky to get flat. I was thinking thicker material (acrylic sheet or solid surface) applied in a press. Thoughts anyone?

I used DMEasy spray contact for the laminate and had the glass guys glue the mirror with that same mastic.

I doubt it's really a balanced construction at all. I think it's more that the solid mahogany is much harder for the laminate to "pull" than mdf which has little resistance. Oh and my frame was only about 13/16" thick FWIW.

JeffD

Am I reading you right in that you glued the mirror on with contact cement?

I would not glue the mirror to the door use either clips or aluminum moulding so that the mirror is loose and can move independent of the door.