[Cob] RE: Oiling Cob/NY Times

[Jack Stephens]

Brilliant, Bernhard. 

Thank you for your thoughtful input to the discussion. There's plenty of
moisture to be found in the Oregon Cascades where you live, so your
experience is especially valuable to me. 

Look for an article about earthen floors in the NY Times this coming
Thursday, February 8th. 

Very best regards,

Jack

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-----Original Message-----
From: coblist-bounces at deatech.com [mailto:coblist-bounces at deatech.com] On
Behalf Of Bernhard Masterson
Sent: Tuesday, February 06, 2007 9:23 AM
To: coblist at deatech.com
Subject: [Cob] RE: Oiling Cob

I'd like to put in my two cents after living in my cob house with an oiled
floor for the last three years.  I feel living on an oiled cob floor is the
best floor experience I have ever had.  Feels slightly springy, and feels
wonderful to lay once it is heated by the sun.  Sun bathing in January in
Portland, OR is a pretty good deal.  Guests routinely exclaim the most about
the beauty of the floor.  And when I practice Tai Qi or Qi Gong I feel more
energy from the earth than in any other building.        Using local gravel
(sub-floor) sands and clays and then oiling has a far smaller eco-footprint
than any other option I can think of including fired clay tile from Mexico,
bamboo shipped from Asia, etc.   The processing and transportation is
minimal by comparison.     The linseed oil on our floor alone does not make
it water proof since there is still some porosity.  An annual beeswax and
oil rub creates a surface upon which water beads up on and is easy to clean.
The only oils recommended for applying to floors are those that are
oxidizing oils.  Linseed and walnut oils are both oxidizing oils which mean
that they "dry".  Boiled linseed oil does have toxic additives to decrease
the drying time which is why you will often find raw linseed oil
recommended.  Raw linseed oil and walnut oil take much longer to dry.  How
long depends on the porosity of the surface to which they are applied and
drying conditions.  The more porous the surface the thicker the application
and the longer the drying time.  Walnut oil on wood takes about two weeks.
Walnut oil on cob about three weeks.  On my heated cob bench the walnut oil
took about one week.  By comparison boiled linseed oil dries in under a week
on unheated cob.  Because the porosity of cob is higher than wood you can
apply many, perhaps seeming endless, coats that penetrate/soak in.  Less oil
is absorbed with each coat provided you have given adequate time to dry.
Two to four coats of oil will suffice depending on how much you thin each
coat with solvent.  You can speed the drying of raw linseed oil by first
setting it in the sun in a shallow pan for a week.  Cover the pan to keep
out dust but allow the moisture to evaporate.      When applying the oil you
can eliminate the turpentine by applying hot oil to warm floors or adding a
citrus solvent.  The thinner the oil the better the penetration.  Great
caution should be used when heating oil to avoid a fire.  And yes when the
oil dries there is a smell of paint/rancidity that persists for several
weeks.  I did not find it overpowering and feel that several on the list
have exaggerated the level of smell or health risk.  After a few weeks it
completely disappears.     I have never seen any mildew on any oiled cob
that I have built even where condensation from the aluminum frames on my
picture windows drips on to the floor.  If there is enough moisture in the
cob to mildew, the structure has far greater problems than moldy floors.-
Bernhard 
_________________________________bernhard_masterson at hotmail.com
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