[Cob] Re: oiling cob

[Barbara Roemer & Glenn Miller]

Maybe the answer to how and whether and with what to oil cob is more complex
than it seems on the surface.  I have oiled exterior cob walls to give a
little more weather resistance in our climate and had no rancid smell -
none, ever.  But we used cheap linseed oil with heavy metal driers.  The
smell soon dissipates, which means the particles are volatilized and drift
off to join the rest of the goo in the air - bad news.  I live in a heating
climate - cool, rainy winter.  While we normally have about 65" of rainfall,
we also usually have only three days of overcast before it's sunny.  Our
summers are hot and bone dry from May to October.  Maybe it's our relatively
"dry" climate - that is, low humidity, concentrated periods of rainfall
alternating with sunshine, and hot dry summers - that keeps oiled cob from
molding here.

I have oiled our earthen floor on three different occasions in four years,
with many coats each time.  I used low voc products from green suppliers who
state their products use citrus thinners and no heavy metal drying agents.
The smell lasts for about three days (done in summer and fall), and I'm very
sensitive to it, so would recognize if it went rancid or smelled longer than
that.  I've used Hard Oil #9 along with beeswax, and had very little smell
even after the first day.  While our floor is not heated, during the coldest
parts of winter we set up a little heater in the bathroom, and the floor
gets quite warm and stays that way for hours.  It never smells or gets
rancid.  If you don't apply too much oil, it shouldn't sit on the surface
and be concentrated enough in any one place to go off.

Bill Steen, on the S-B-R-Us Yahoo list, of the Canelo Project outside of
Tucson, where there is about 12" of rainfall annually, has been putting in
earthen floors and oiling them for about 15 years.  He is about to publish a
long-awaited revision to his original floor book (pretty much ignore much of
the first one).  He dries raw linseed oil out in the sun in thin layers in
cafeteria trays and then oils his floor.  No driers, and usually now no
thinners, I believe, although for years, he cut the oil with turpentine, and
I've never smelled any residue in his buildings.  I was not there
immediately after any oiling, though. Bill posted recently about how his
floors have held up over the years, so anyone with interest can check out
the SB archives, or soon, buy an e-copy of his new floors book on his
website: <caneloproject.com>  .

On the downside, I've seen both oiled and unoiled cob walls on the moist,
temperate California coast with a shaggy fungal coat.  Even dirt will mold
under the right conditions - usually warmth & moisture together.  It's the
organic material in the soil being broken down by decomposers.  My
experiences are limited but it seems that mold has more to do with climate,
and rancidity with heavy applications that can't be absorbed by the cob.
I've mixed oil into clay, both for walls and floors, and then oiled it
afterward, with no ill effects. I'd like more info from those of you with an
experience of mold or rancidity - what are the local conditions?

23 cents' worth Barbara