[baidarka] Borates, Glycols

Craig O'Donnell (dadadata@friend.ly.net)
Fri, 1 May 1998 22:41:44 -0400

Message-Id: <l03110700b17037fc90e2@[]>
Date: Fri, 1 May 1998 22:41:44 -0400
From: "Craig O'Donnell" <dadadata@friend.ly.net>
Subject: [baidarka] Borates, Glycols

Here is the definitive wood-rot document as far as I am concerned. A
version appeared in BOATBUILDER magazine. This is from Dave Carnell's web

Chemotherapy for Rot


Once rot gets a toehold in wood it is difficult to cure completely-it is
like a cancer. Digging out the rotted wood will still leave spores and
water in the sound wood. After you fill in the cavity with something like
epoxy, the rot continues to flourish underneath. Products promoted to make
rotted wood sound and stop rot penetrate only until they meet water, with
which they do not mix. Under the solid repair rotting goes on. With one
exception (more later), the commercial products sold to treat dry wood to
prevent rot are completely ineffective against established rot in wet wood
because they are dissolved in petroleum solvents and oil and water do not

There are two commonly available inexpensive materials that will kill rot
in wood and prevent its recurrence. First, there are borates (borax-boric
acid mixtures) which have an established record in preventing rot in new
wood and in killing rot organisms and wood-destroying insects in infested
wood. Second, there is ethylene glycol, most readily available as auto
antifreeze-coolant. Glycol is toxic to the whole spectrum of organisms from
staphylococcus bacteria to mammals. All of the published material on its
effectiveness against wood-destroying fungi and insects that I am aware of
is the result of my investigations over the past 15 years

Both borate solutions and glycol penetrate dry and wet wood well because
they are water-soluble; in fact, penetration by glycol is especially helped
by its extreme hygroscopicity-its strong attraction for water. For both,
the fact that they are water-soluble means they are not permanent solutions
to rot in wood that is contnually exposed to water-below the waterline and
in ground-where they will eventually be extracted-dissolved out

I first was interested in glycol as a wood-stabilizing agent, where it is
in many ways superior to polethylene glycol (PEG), and it was during this
work that I realized the useful effect of glycol on organisms, though I
was pretty dense in interpreting the first experiment

The ladies immerse the stems of greenery such as magnolia branches in
glycerin to keep them green. Glycol is very similar to glycerin in all its
physical properties and much cheaper, so I stuck a magnolia branch in
antifreeze. The next day it was brown. After the third attempt I tumbled to
the fact that the glycol was killing the greenery.
This was the reason that glycol never replaced glycerin in applications
such as a humectant for tobacco and an ingredient of cosmetics and
pharmaceutical ointments, though it had all the desirable physical

I had two 2" thick slabs of a 14" diameter hickory tree that had just been
cut. I treated one with antifreeze and left one untreated. I was looking
at wood stabilization, not rot prevention. After about six months stored
inside my shop the untreated control was not only cracked apart, but it was
sporting a great fungal growth, while the treated slab was clean

The local history museum wanted to exhibit two "turpentine trees", longleaf
pines that had many years ago been gashed to harvest the sap that made
everything from turpentine to pine tar. The trees delivered to us after
cutting were infested with various beetles and had some fungal growth. I
treated them with antifreeze outside under a plastic tarpaulin every few
days for three weeks. They were then free of insects and fungus and have
remained so after being moved inside and installed in an exhibit over four
years ago. I took three pieces from a rotting dock float that
were covered with a heavy growth of fungus, lichens, etc. I treated one
with antifreeze painted on with a brush, the second with a water solution
containing 23% borates (as B2O3), and left the third untreated as a
control. They were left exposed outdoors and were rained on the first
night. By the next morning the growth on the antifreeze-treated piece was
definitely browning and the borate-treated piece showed slight browning.
After two months exposure to the weather the growth was dead on the
antifreeze- and borate-treated pieces and flourishing on the control

I have a simple flat-bottomed skiff built of plywood and white pine, which
has little resistance to rot. After ten years some rot developed in one of
the frames. It may have begun in the exposed end grain. It consumed the
side frame, part of the bottom frame, and part of a seat brace fastened to
the side frame. The plywood gusset joining the side frame to the bottom
frame was not attacked. I excised the rotted wood, saturated all with
ethylene glycol antifreeze to kill all the rot organisms, and there has
been no further deterioration in four more years afloat with wet bilges. I
have not replaced any pieces, as I am building another boat that can
replace it; that is more fun, anyway

I have a 60+-year old case of the fungus infection known as "athlete's
foot". Many years ago it infected the toenails extensively. The whole thing
was pretty grotesque. My dermatologist and druggist both assured me there
is no known cure. About six years ago I started using antifreeze applied
under the nails with a medicine dropper about every five days. The
professionals are technically right. I have not completely cured it, but
the nails have grown out pink and thinned almost to the ends and I never
have any trouble with blistering, peeling, or itching between the toes as I
had had for six decades. No drug company is going to have any interest in
this because the information has been in the public domain for so long that
there is no opportunity for any proprietary advantage. The various
wood-rotting organisms cannot be anywhere near as tough

There are two types of borate products commercially available for treating
wood-solid sodium octaborate for making solutions in water (Tim-BorŽ and
Ship-BorŽ) and a 40% solution of sodium octaborate in ethylene glycol
(BoracareŽ). Their equivalents and more concentrated solutions can be
easily prepared from borax, boric acid, and antifreeze at much lower cost.
Keith Lawrence, editor of Boatbuilder offered to sell me advertising if I
wanted to go in the business, but I might run afoul of patents (preparation
for individual use is not prohibited), I would have to get EPA
registration, and I could not deliver products anywhere near as cheaply as
they can be made from raw materials available at your supermarket,
drugstore, and discount store

Glycol by itself has one big advantage over solutions of borates in either
water or glycol. Glycol pentrates rapidly through all paint, varnish, and
oil finishes (except epoxy and polyurethanes) without lifting or damaging
those finishes in any way. You can treat all of the wood of your boat
without removing any finish. The dyes in glycol antifreeze are so weak that
they do not discolor even white woods. Once bare wood has been treated with
glycol or the borate solutions and become dry to the touch it can be
finished or glued. If a borate solution leaves white residues on the
surface, it will have to be washed off with water and the surface allowed
to dry.
This is my preferred process to treat rot. Once you find
soft wood or other evidence of rot, soak it with antifreeze even if you
cannot do anything else at the moment. Paint it on or spray it on with a
coarse spray. Avoid fine mistlike spraying because it increases the
likelihood that you will breathe in unhealthy amounts of glycol. Put it on
surfaces well away from the really damaged wood, too. Use glycol lavishly
on the suspect wood, which will readily absorb 10-20% of its weight of

Next dig out wood that is rotted enough to be weak. Add more glycol to wet
the exposed wood thoroughly. Then add the 25% borate solution of the recipe
below so long as it will soak in in no more than 2-3 hours. Then fill in
the void with epoxy putty and/or a piece of sound treated wood as required.
The reasons I use borates at all are: 1) it is a belt-and-suspenders
approach to a virulent attack, and 2) over a long period glycol will
evaporate from the wood; especially, in areas exposed directly to the sun
and the high temperatures that result

If there is any question about water extracting the glycol or the borates,
you can retreat periodically with glycol on any surface, painted or bare,
and with borate solutions on bare wood

Glycol's toxicity to humans is low enough that it has to be deliberately
ingested (about a half cup for a 150 lb. human); many millions of gallons
are used annually with few precautions and without incident. It should not
be left where children or pets can get at it, as smaller doses would harm
them, and they may be attracted by its reported sweet taste that I have
confirmed by accident. The lethal dose of borates is smaller than of
glycol, but the bitter taste makes accidental consumption less likely.


Solid sodium octaborate; dissolves in water to make approx. a 10% solution
containing 6.6% borate (B2O3 molecules); about $3/lb. plus shipping.

Same as Tim-BorŽ; $19.95/lb. plus $2 shipping.

40% solution of sodium octaborate in ethylene glycol; 27% borate content;
$70/gal. plus shipping.

Home-Brew Water Solution of Borates:
Based on U.S. Navy spec -- 60% borax-40% boric acid (this ratio gives the
maximum solubility of borates in water); 65% water, 20 %borax, 15% boric
acid; 15.8% borates; borax costs 54 cents/lb. (supermarket), boric acid
costs about $4/lb. in drug stores (sometimes boric acid roach poison, 99%
boric acid, is cheaper in discount stores); equiv. to Tim-BorŽ or Ship-BorŽ
at 30 cents/lb. To make this solution mix the required quantities and heat
until dissolved. The boric acid, in particular, dissolves slowly. This
solution is stable (no crystals) overnight in a refrigerator (40°F.), so
can be used at temperatures at least as low as 40°F.

Home-Brew Glycol Solution of Borates:
This is equivalent to Bora-Care° diluted with an equal volume of glycol to
make it fluid enough to use handily; 50% glycol antifreeze, 28% borax, 22%
boric acid. To make a stable solution you mix the ingredients and heat till
boiling gently. Boil off water until a candy thermometer shows 260°F.
(This removes most of the water of crystallization in the borax.) This
solution is stable at 40°F and has a borate content of 26%. With antifreeze
at $6/gal. and borax and boric acid prices as above, this is equivalent to
Bora-CareŽ at about $15/gal.


Craig O'Donnell
The Proa FAQ <http://www.cyber-dyne.com/~jkohnen/proafaq.html>
The Cheap Pages <http://www.friend.ly.net/user-homepages/d/dadadata/>

-- Professor of Boatology
-- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.