Woodworking Talk banner
1 - 15 of 15 Posts

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #1 ·
I’m cutting some MDF window casing for my daughter to use as a frame around her bathroom mirror. Its 3’x6’ and she is installing it to the glass with glue. My question is should I try to use Biscuit joiners to help her assemble them?
I know there are a lot of people here that are dead set against them and I’m not so sure they will hold up on the MDF that they are made from.

 

·
Registered
Joined
·
1,932 Posts
I'm guessing you mean biscuits in the miters? Yes you can do that but you may only be able to fit FF (faceframe) size biscuits and not all biscuit machines cut that size, it requires changing to a smaller cutter than the one for standard biscuits. I've done this with window trim and MDF moldings. That said, 3'x6' is a sizable mirror and MDF doesn't have any strength. How do you plan to create the rabbett for the mirror? Will it be hung from the frame or will the frame just be decorative around the perimeter but not connected to the mirror? Why not use solid wood casing? You could run a backing piece behind the casing to form the rebate and allow it to lap over the back of the miters and tie across them. It would give you more purchase if the mirror will be hung from clips and wire. You wouldn't be able to put decent screws just in the MDF, too weak and too thin.

Biscuits have their place, it's just that advertising leads folks to believe they work in situations where they don't actually work. Miters and faceframes are a perfect use for biscuits. Edge gluing boards for a panel or table top, not so much. Most of the kitchen cabinet manufacturers use biscuits in the now popular mitered doors. They use a disc style biscuit, not a football shape, for deeper reach but FF footballs are fine for casings.
 

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #3 ·
Well I guess it’s a good thing I didn’t try yet because I only have one blade. I just thought it might make it easy for her assemble because she needs a way to keep the miter cuts flush while the glue dries.

Actually I’m not sure what she plans on using to glue it with. She’s not going to rabbit. The sides & bottom aren’t visible and it would take a pretty tall person to see the top. I guess she could use calking if she wanted to.

She reads all those home decorating magazines and this project was in one of them. The mirror is nothing fancy and is glued to the wall. I recommended not trying to remove it, because we not know how much work is going to be behind it.

She’s been pretty busy decorating her house and actually I’m quite surprised at some of the things she has done from those magazines.
 

·
where's my table saw?
Joined
·
31,266 Posts
the mirror is glued to the wall

If that's the case, just make your miters accurately and starting at the bottom piece, glue them to the wall also, and work your way around. Use blue painter's tape to hold them in place until the dabs of glue set up. It won't take much glue. OR you can use foam double sided tape with small squares along the edges for an instant application, and glue in the miters.
 
  • Like
Reactions: Sleeper

·
Old School
Joined
·
24,017 Posts
The sides & bottom aren’t visible and it would take a pretty tall person to see the top. I guess she could use calking if she wanted to.
It sounds like the trim will be applied to the face of the mirror, unless there's enough gap at the sides and bottom. Remember to paint the back side, as there will be a reflection of it in the mirror.

Most mirrors are either coated on the back, or it's the silvering. The edges of the mirror should have been coated when cut to size with a clear acrylic to prevent air from getting to the edges. When mirror is cut, the silvering edge if uncoated can oxidize from the exposure, and start to turn the mirror looking black. Most caulkings are not usable because they will react with the silvering.

I wouldn't use biscuits. I would cut the moulding to fit properly, and set in place to check it. You could use Liquid Nail (LN-901), as an adhesive. Apply to the back of the trim keeping it away from the inner edge. Place the moulding onto the mirror, and then remove. Allow a few minutes for the adhesive to flash off, and install the trim. It should just stay where you put it. You could ease it around if necessary.

Or, use Palmer Mirro-Mastic (available in tubes). Just apply to the trim (again, away from the inner edges), and press in place. That stuff is thick, like peanut butter, and the moulding won't fall off. Both adhesives needs a little thickness to get a good bond. You don't want any squeeze out though.






.
 

·
Really underground garage
Joined
·
2,552 Posts
One thing you can do....and it's just a "trick".And like any trick,they may not be appropriate at all "party's"


Instead of biscuits,imagine this:

Take a pce of 1/4 ply.....and to be fair the trick works much better with real wood,like a 1x?....but anyway.Rip a pce of 1/4 ply so that it is basically the same width as your casing.Now instead of mitreing corners,like you will on casing....you will be butt cutting them.The next thing is,you are NOT trying to hold it "flush" with the casing.Instead it's held proud of the outside edge by exactly how much rabbit you want to create on the mirror side.

The reason for butt jointing...and run the vert legs first...is:When you install this "extra" member on the back of casing you are creating a lap joint.Getting a free rabbit,and adding an "element" to the trim.Never pass up an opportunity to create a stronger joint.....the trick is to do it as efficiently as possible.
 
  • Like
Reactions: Sleeper

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #7 ·
...Use blue painter's tape to hold them in place until the dabs of glue set up. ...
:huh:Tape! That would work to hold it in place. I never think to use tape to hold anything. Thanks!

I... Remember to paint the back side, as there will be a reflection of it in the mirror.

..... Most caulkings are not usable because they will react with the silvering.

.... You could use Liquid Nail (LN-901), as an adhesive. Apply to the back of the trim keeping it away from the inner edge. Place the moulding onto the mirror, and then remove. Allow a few minutes for the adhesive to flash off, and install the trim. It should just stay where you put it. You could ease it around if necessary.......
Thanks, this all great info and stuff that I didn’t think or know about. I’ll be sure to let her know. :thumbsup:

.....Now instead of mitreing corners,like you will on casing....you will be butt cutting them.The next thing is,you are NOT trying to hold it "flush" with the casing.Instead it's held proud of the outside edge by exactly how much rabbit you want to create on the mirror side......
Thanks, I think the book said to use these molding blocks, but I told her I could miter them so there wouldn’t be as many pieces. She said she could not find the blocks, but I think she may have been looking in the wrong places. :smile:

 

·
John
Joined
·
3,028 Posts
:huh:Tape! That would work to hold it in place. I never think to use tape to hold anything. Thanks!


Thanks, this all great info and stuff that I didn’t think or know about. I’ll be sure to let her know. :thumbsup:


Thanks, I think the book said to use these molding blocks, but I told her I could miter them so there wouldn’t be as many pieces. She said she could not find the blocks, but I think she may have been looking in the wrong places. :smile:

Hi Johnny - Here's another option for adhesive:
http://www.homedepot.com/p/Loctite-...ction-Adhesive-1589157/203009262#.UkAuFcco670

It dries clear and you only need to hold the piece in place a few seconds before it sets up enough to hold it in place, full cure takes 24 hours though. Use blue painters tape as a backup till then.

Her's a link for rosette blocks
http://www.homedepot.com/webapp/catalog/servlet/Search?keyword=rosette+block&Ns=None&Ntpr=1&Ntpc=1&selectedCatgry=SEARCH%2bALL

Using the blocks would probably simplify things. Install the blocks first and then just cut the trim to fit.

Good thing you didn't have her try to remove that, a mirror that size would be HEAVY.

Good Luck:smile:
 
  • Like
Reactions: Sleeper

·
where's my table saw?
Joined
·
31,266 Posts
  • Like
Reactions: Sleeper

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #10 ·
Thanks John & Bill for the links, :thumbsup:

I actually have an unopened tube of Loctite Clear Power Grab and I can't remember what I originally bought it for. :laughing:
 

·
Old School
Joined
·
24,017 Posts
I actually have an unopened tube of Loctite Clear Power Grab and I can't remember what I originally bought it for. :laughing:
I haven't tried that particular adhesive on mirror to know if it will attack the silvering. When it happens, it could be over weeks or months...maybe not right away.



.
 

·
John
Joined
·
3,028 Posts
I haven't tried that particular adhesive on mirror to know if it will attack the silvering. When it happens, it could be over weeks or months...maybe not right away.







.
If she is gluing directly to the glass, I wouldn't think it would attack the silvering. Along the edge or back may be another issue. Any outgassing should disperse in the short term.
 
  • Like
Reactions: Sleeper

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #14 ·
Well it looks like the instructions do call for liquid nail and she is going to use the corner blocks now that she knows where to find them. So that means no miter cuts.

I have an old Stanley plastic miter box & saw that I'm going to give her so she can do this stuff herself. :shifty: Who knows maybe she will end up a woodworker someday. :laughing:
 

·
Registered
Joined
·
5,607 Posts
Discussion Starter · #15 ·
It sounds like the trim will be applied to the face of the mirror, unless there's enough gap at the sides and bottom. Remember to paint the back side, as there will be a reflection of it in the mirror................
So I forgot to tell my daughter about painting the back and she just discovered it it on her own. :eek: Oh well! :laughing:
 
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top