[Cob] Re:colors and FLOOR PARTY

[Barbara Roemer and Glenn Miller]

Suggestions/experience:

Our floor is rock hard, though not marble smooth so a broom drags over it a
bit.  That problem could have been solved with the right trowel.  What we
did (long, skip if you're not into details!):

Gravel
Scoria or lava rock for insulation
cobbish mix of long straw, clay, lots of sand
at this point we set in chunks of plywood that were the size of the tile
patches plus their grout lines where we planned to lay them at the back door
and the bathtub.  The ply was thickness of the next two layers, about 3/4"

finish layers:

clay/lots of sand/finer chopped straw:  result - quite a few cracks of a
little more than 1/8", despite test samples that didn't crack (they weren't
big enough - test at meter square patches, full depth, drying in the same
area where your floor will be).  Trowelled out with wood trowels and steel
pool trowels.  Used coarse sand so it would remain permeable for next layer.

Final:

Linseed oil worked into the final mix - about a half gallon to a quantity
that covered about 120 sq ft, at 1/4" depth.
Clay, finely screened (window screening) straw, coarse sand.
Trowelled with wood trowel to force mix into cracks.  No more cracking, but
a little too much tooth.  Still beautiful, no cracks, very hard, stands up
to constant foot traffic in and out the back door which is in the bathroom.
Gets mopped weekly, swept in between.  Troweling with steel trowel would
have produced a smoother finish, as would finer sand.  The coarse sand let a
lot of oil penetrate, contributing greatly to the hardness.  Floor continued
to harden over several months.

Finish:

two coats Bio-Shield Hard Oil #9, $$$ (we could have used boiled linseed had
we done the floor earlier and been able to keep the windows open, but it's
just too volatile for too long in cool fall or winter weather when the
windows are mostly closed).

After the floor was oiled, I screwed two big screws partway into the plywood
pieces so I could remove them by yanking up on them (had to cut away a
little floor mix that had extended over the ply edge - used a lino knife).
Laid a thinset mortar bed in those tile spaces to have something that would
level easily and wouldn't allow movement or any spaces between itself and
the tile.  Tile is kind of thin Mexican travertine, so cracks if there are
any voids under it.  Laid another thinset coat in which I set the tiles.
Let it all set up after carefully cleaning off the earthen floor, easier
because it had been oiled - the thinset will leave a light grey permanent
stain otherwise.  Picked out the excess thinset between the tiles with a
pencil, a knife, a stick.  Mixed some more floor mix with lots of oil and
grouted the tile with that - matches the floor perfectly, is at the same
level, looks great.  Also set tiles up the wall in a toilet niche just with
the floor mix, no thinset.  Screed boards makes it easy to work larger
areas. Our dark red clay makes a dark red brown floor - shows dusty
footprints, but not much else.