Can I epoxy granite tiles together with a mitred joint?

[J Kelly]

I am installing a fireplace surround with 1/2" thick 12x12 granite tile.
I would like to mitre the tile so it returns into the firebox about 3".
Can I use epoxy to glue up 2 mitred edges and install the single
unit in thinset?
A stone guy I know said he would not glue it as described above, but
would install the outside mitre pieces first and then install the inside
3" pieces using fortified grout at the mitre joint.
What do you think?

[Mark D.]

You can do it either way,  so the question is do you want to do the extra step of epoxying the mitered pieces? I am assuming that:
a) These pieces are not going to get super heated
b) The cut edges are being glued together so that the polished faces are what is showing (if that is incorrect you will still have to polish the newly cut face, or at least color enhance it).

If the glue joint is at the front of the hearth opening then I see nothing wrong with doing it either way. It will mean that you have one less grout joint and that the missing joint is right on the corner of the return to the hearth.

You may have a problem with chipping when you cut the pieces at a 45 degree bevel. If you do you can fix it up with the epoxy. If the granite is too brittle to hold the edge then try to glue a piece to the back of the piece facing out into the room after polishing the 1/2" edge which will be exposed in front of the newly glued on piece.

Don't forget to color the glue to match the base color of your stone.

Mark

[J Kelly]

Mark,
Thanks for your reply.
I believe you are recommending a butt-joint if the mitre joint doesn't work.
I agree.  That is my "Plan B" solution if the granite is too brittle to mitre.

I plan to use Defusco 29 minute epoxy, knife grade.
     What does knife grade mean?
     How do I color the epoxy  to match the base color of the stone?
     By "super heated" do you mean the temperature that would be produced by a fire?

John

[Mark D.]

There are two consistencies of stone glue:
Flowing - like molasses
Knife grade - like warm peanut butter.
Knife grade is easier to use, especially on anything that is not horizontal, as the flowing is more affected by gravity. The 29 minute epoxy is a mercaptan epoxy so it is made to take temperature changes. Here is the link to epoxies:
http://www.defusco.com/glues-epoxy-polyester-etc-epoxies-c-82_500.html?osCsid=ebe05d4cdc8374a92ecd4d3359f21015

For color, we have quite a selection. Here is that link:
http://www.defusco.com/glues-epoxy-polyester-etc-coloring-kits-c-82_504.html
Color the stone to match the base color of the granite.

Super heated would be if you were lining the bottom of the fireplace with granite, not the hearth opening.
Remember, if you do a butt joint you will have to polish the newly cut edge as it will be exposed. The pads I recommend are here:
http://www.defusco.com/resin-dry-polishing-pad-full-set-p-2009.html