Gluing MDF Miter Joints

MDF soaks up ordinary wood glues, compromising the bond. Here's advice on priming the joint before gluing, or using a specialized adhesive. February 25, 2009

Question
Im doing a cabinet installation job and Im used to real wood moldings, where I use pro bond and pressure bond my miters and install them as one unit. Now Ive run into a molding made of MDF and the same glue is not working at all. The MDF is absorbing the glue and I cant get a proper bond. Is there another adhesive or wood glue someone would recommend for doing these kind of moldings?

Forum Responses
(Adhesive Forum)
From contributor O:
Prior to gluing up your miters, try sealing the cut ends with a latex sealer. Let it dry and then glue with your favorite product in the usual manner. I know this extra effort is pain-staking/time consuming - but it will work!



From contributor J:
Fastcap's 2p10 is the ticket on that MDF stuff. Keep in mind though, it sets up in less than ten seconds.


From contributor D:
I believe that you should keep in mind the MDF board is made from the wood fiber like what in the paper, so you should use the adhesive that has less water content in order to prevent the water and humidity absorbing. Then you will have less problems on it.


From contributor A:
I agree with contributor J. Fastcap's instant CA glues are excellent for bonding MDF. The gel gives a slightly longer assembly time than the medium or thick. Hot melt reactive polyurethane glue from Franklin is a good MDF glue but is not clear like Fastcap which can be a problem with veneered MDF. Either adhesive system only requires pressing the two pieces together by hand and holding for 30-45 seconds.


From contributor B:
Yes, the MDF will suck the glue right into it. Just spread a light film of glue on the MDF joint with your finger, let it suck in and dry for a few minutes. Then glue as normal. The first bit of glue acts like a sealer when it dries a bit. Not that complicated.