A question for mitreing maesstro's - Tile Advice

[Dumbo]

Why is that when mitreing externsl corners with tiles they are jointed using epoxy , I have ideas as to why it may be done but would actually like to know the cold hard truth .
Thanks in advance

 

[Flintstone]

For strength and appearance.

 

[Dumbo]

For strength and appearance.

But why strength does it need and I could get appearance with grout

 

[Flintstone]

You can't get the same appearance with grout I assure you ! Same colour maybe. Your taking the edge of the tile to a very thin point which leaves it week.

 

[One Day]

Trade secrets!
Painful trial and error.

Resin looks shinier than grout and is infinitely stronger if done correctly.
Plus you can mix colours.