Oxalic acid is for cleaning cedar and redwood decks, not treated pine.
For treated pine, the standard chemical used to be sodium hypochlorite
(common household bleach). Many people still use that, but a lot of
experts are starting to recommend against it, because the chlorine can
damage the wood. It attacks the lignin in the wood and weakens the
wood surface structure.
A lot of the home improvement gurus now recommend sodium percarbonate,
which when added to water turns into hydrogen peroxide (oxygen bleach)
and sodium carbonate (washing soda - remember the old Arm and Hammer
washing soda that you used to be able to buy in the laundry aisle?).
The combination is an effective deck cleaner and brightener which does
not damage the wood and is very safe to use.
You can buy 2-pound jars of pure sodium percarbonate at
thechemistrystore.com for about two bucks a pound, plus shipping. Or
you can buy a bucket of "Oxy Clean" at the supermarket - it's the same
thing except its not 100% sodium percarbonate - it contains a large
percentage of sodium carbonate filler which is a less expensive
You can also buy a bucket of Tri Sodium Phosphate (TSP) and throw a
couple of ounces it in a bucket of warm water together with some
household bleach to create a very effective deck cleaning solution, if
you don't believe the warnings about using chlorine-based bleaches on
You can also buy a bucket of oxalic acid there too.
Please note that oxalic acid IS a toxin to humans. It can be absorbed
through the skin. Use with care.
Why not just buy hydrogen peroxide and washing soda, and mix them? They're
both readily available, cheap as dirt, and bound to be less expensive and
easier to find than sodium percarbonate.
If you only "used to" be able to buy washing soda in the laundry aisle, either
you're shopping in the wrong stores (e.g. Wal-Mart), or you're not looking
very hard. I don't have any trouble at all finding washing soda in the laundry
aisle of my neighborhood Kroger grocery store.
Doug Miller (alphageek at milmac dot com)
When you say hydrogen peroxide is "readily available" and "cheap as
dirt" I of course think of those brown plastic 16oz bottles they sell
everywhere, from WalMart to Walgreens. There are two problems:
1) That's only a 3% solution. You would have to use it full strength.
So, not sure it would much cheaper, if at all.
2) The reason it's in a brown plastic bottle is that it's unstable.
Has a short shelf life. The powdered sodium percarbonate keeps much
longer, as long as you keep the lid on it to keep the moisture out.
You can buy much stronger hydrogen peroxide at some pool and spa supply
stores, but it's expensive - and at high concentrations is somewhat
dangerous to handle.
Sodium percarbonate is easy to find. It's the active ingredient in
OxyClean and other oxygen-based cleaners which line the supermarket
shelves (but as I said, those products contain a lot of filler - they
are not 100% sodium percarbonate). Most pool and spa stores carry
"oxygen shock" which is sodium percarbonate. Many mail-order places
sell it. Type the words "oxygen" and "deck" and "bleach" into your
internet search engine, and you'll get hundreds of hits.
WalMart and Meijer used to carry it in their laundry products aisle but
they no longer do. I also checked two or three other chain stores and
they don't carry it either. Haven't checked Kroger yet - but I will.
While I'm there, I'll also look for "20 mule team Borax" which WalMart
also stopped stocking (I've had good results using a Borax and vinegar
solution for spraying on treated pine and vinyl siding to
prevent/destroy mildew and algae).
Speaking of WalMart, is it just my wild imagination, or do I sense a
slight change in their business model? Besides Arm and Hammer Washing
Soda and 20 Mule Team Borax, there are other low-volume products I have
seen disappear from their shelves recently. In the past, I had the
impression they wanted to be all things to all people. Now lately I
seem to perceive a trend to eliminate some of the low-volume stuff.
They may save a nickel in the near term, but people may start to
re-discover other stores. That may be a good thing.
Any sail boats in your area? Oxalic acid was (if it still is not)
the bleaching agent of choice among sialboat owners for cleaning their
When I lived in the Annapolis area of Maryland every Drugstore sold it
and every marina had it in stock in many sizes... Drugstores should be
able to order it for you in any part of the country... Also works
well on convertible vinyl tops...you just have to have the hose
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