Cleaning
Barn Timbers
I'm in the
process of converting a 150 year old barn into a residence in
Cape Cod
. The interior beams are Douglas Fir and have significant stains
from dirt and other agriculture related materials. I was wondering
if oxalic acid would be the best route to pursue, or if the
toxicity of it is such that an interior application would be
unwise. The beams themselves will remain exposed in living spaces
so aesthetics are as important as safety.
Ha! I like your
euphemistic phrase, "other agriculture related
materials." We can speak plainly here, and if we're dealing
with horse manure, we can say “horse manure.” One of the most
important aspects of cleaning is to understand what the dirt is
made up of. So, if we have manure, then we not only want a good
looking surface, but one that is disinfected and clean enough to
be healthy to live with.
If you want to
preserve the character of the beam surfaces always test out least
aggressive cleaning methods first. For example, simply wash the
surface with warm water and a coarse rag such as burlap. If that's
not effective, try using a soft bristled brush; not so good? Use a
stiff bristle scrub brush. Still could be better? Add just a
capful of mild detergent (ordinary dish washing detergent like you
use at the kitchen sink) and rinse with plain water. OK, there are
still deposits of grunge and grime? Use a low-powered detergent,
such as Simple Green. Not good enough? Then try a high-powered
detergent such as Tri-Sodium Phosphate, but first mix it at half
the recommended concentration. See? Least to most aggressive, just
stop in the testing process when you get the results you are
after. Big Benefit: you'll do the least amount of work and get the
biggest bang for your buck.
One reason to
use a scrub brush rather than a high-pressure power washer is that
you want to contain the dirt so you don't spread the contamination
all around with a powerful blast of water. In any case, wear
protective clothing, respirator, goggles, face shield, etc., when
doing this sort of cleaning; and follow effective personal hygiene
and cleanup practices after every work session.
On large cleaning jobs you can step up production by
applying cleaning solutions and water with an ordinary
low-pressure garden sprayer or garden hose and nozzle. Also, the
3M “DoodleBug” scrubbing device on an extension pole will
increase production. Often the high-pressure power washers cause
damage to the wood surface. It is possible to
operate a power washer without causing damage, but I have
seldom seen one used with the "artistic nuance"
required.
OK, after
cleaning, if you've still got stains and uneven appearance you can
try more aggressive chemical treatments, which will work better on
the clean surfaces. I would start by testing ordinary household
bleach in a 1-part bleach to 20-part water solution, stepping up
the concentration gradually to not more than 1-part bleach to
5-parts water. This will kill some types of unhealthy biological
organisms and do away with some types of surface stains, evening
out the appearance. No good enough? Then try a two-part oxygen
bleach system.
Then you might
need to try oxalic acid. Oxalic acid must be treated with caution
and respect when it is used, but interior use and surfaces treated
with it are relatively safe after treatment. When using any
chemicals (even relatively safe and familiar ones such as dish
detergent) always follow all of the manufacturer's instructions,
and the manufacturer's Materials Safety Data Sheet for that
product.
Keep in mind
that this is a barn, and you are seeking a balance between the
modern sense of "brand new" surfaces that are acceptable
in a living space and what actually is a rough service area
intended for animals. It is probably that rough character that
initially caught your interest, but if you clean it ALL away you
may loose the character that seemed attractive to you in the first
place.
Contact
Leeke directly for answers to your questions and more information
on techniques for restoring and maintaining your historic
building. Write to John Leeke, Preservation Consultant at
26 Higgins St.
,
Portland
ME
04103
, 207 773-2306; or by E-mail at johnleeke@HistoricHomeWorks.com
or visit his Internet Web Site at www.HistoricHomeWorks.com
Live Video Conferences &
Replays:
http://historichomeworks.com/hhw/conf/vidconf.htm
Historic HomeWorks Forum:
http://historichomeworks.com/forum/
© John Leeke
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