[GSBN] earthen floor sealer in Haiti

[Derek Roff]

Pondering Bruce King's posting, I wonder about the impact on the food 
supply of using food-grade linseed oil.  It's an interesting question, 
both in this specific case and more generally.  I have no idea what 
foods contain food-grade linseed oil, nor who eats them, and I don't 
remember seeing it on any ingredients list for foods that I buy.  I 
also wonder whether it is better for the hypothetical hungry person to 
use a petrochemical on the floor.  Leaving aside the fact that I've 
often seen petrochemicals listed on food labels, I'm thinking that the 
using petrochemicals that are also used in agricultural production and 
transportation might have a greater impact on hunger than the use of 
food-grade oils.  I'm glad Bruce is asking the big questions, and I 
hope someone other than myself can provide some answers.  Not that the 
quantities of anything that we use to seal an earthen floor are likely 
to be a large proportion of our consumption habits, but I think these 
questions are worth thinking about.

Bruce also asked whether the first coat of linseed oil should be the 
one thinned most.  I asked Bill Steen the same thing several years ago, 
since my woodworking background led me to the same expectation.  Bill 
reiterated that full strength oil goes on the floor first, and the 
thinnest oil goes on last.  After annoying Bill with several more 
rounds of "why" questions, here is my current understanding.

Bill pointed out to me that wood and dirt are different.  Whereas even 
a thinned finish applied on wood is unlikely to penetrate more than a 
millimeter or two, thinned linseed oil on an earthen floor might 
penetrate more than an inch/25mm.  This is expensive and of 
questionable value.  Full strength linseed oil will penetrate the 
earthen floor to a sufficient depth (I've read 5-15mm), and 
simultaneously prevent excessive penetration depth by later coats of 
oil.  The second coat, thinned 25%, does not penetrate more deeply, but 
does penetrate some of the smaller pores in that top layer of the 
floor.  Each successive application has more thinner and less oil, in 
order to increase the ratio of oil to earth in the very top layer of 
the floor, without building up a layer of oil on top of the earth.  So 
we are building up a denser earth/linseed oil composite, but avoiding a 
pure linseed oil film surface over the earthen/linseed layer.

That's what I think, and I'm sticking to it until someone sets me 
straight.

Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu

--On Thursday, March 17, 2011 10:20 AM -0700 Bruce King 
<bruce at ecobuildnetwork.org> wrote:

> Also:  am I the only one who is uncomfortable about the idea of using
> edible oils (i.e., food) in construction?  My discomfort is partly
> because that oil is food to all sorts of critters, but also because
> one way or another you are, by using it, sort of removing it from a
> hungry person's mouth.
>
>
> Bruce "Big Mouth" King
> Director of EBNet
> Ecological Building Network
> the art and science of building well
> bruce at ecobuildnetwork.org
> PO Box 6397
> San Rafael, CA 94903 USA
> (415) 987-7271
> follow us on Twitter: @EBNetwork



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu