[Cob] tile over cob

[Barbara Roemer]

Pavel,

I see that you posted your recipes for setting the tile and for grouting
it.  If you can, I strongly recommend a ton of linseed oil in the grout
mix.  The unoiled grout will tend to shrink away from the drier tile as it
dries.  Grout made with clay is both more expansive (and therefore
contractive, too) and less plastic when it dries than what you would
ordinarily buy.  The linseed oil helps to prevent the shrinkage of drying
and makes the grout more resilient and better able to move a bit with the
tile.  Make at least a two foot square sample with your tiles, and grout it
to see what happens.  If it's clay, you can take it apart after it dries
and you've made up your mind.  A four foot square is even better to see
where you get expansion and stress fractures.  You can't do too many
samples!

Hope this helps.

Barbara Roemer