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I quite often spray old wood timbers around customers flower beds.  Makes them look new again.

That wood was stained? are you sure? It wasnt just old wood? It just looks like old gray wood. I could be wrong.

-- Edited by gutterdog on Friday 21st of May 2010 09:34:42 AM

no, it had an old worn out stain/sealer on it...it was in a little better condition under the eaves

I dont know??? I see how, when you wash a house, the SH in the house mix, when some gets on wood it brightens it. I had some leftover love, apple cider, and sprayed it on one of my aluminum sheds. Dwelled it and rinsed with the garden hose. It worked. I dont know???

Yes SH will break down wood fibers, thats why it so very important to rinse, rinse, rinse......
and then rinse a little more. A lot of guys will say is awful for wood, but honestly its been my "go-to chemical" for years. You just have to rinse until all residue is gone, then rinse again.

I use SH on 98% of my house washes. However, if you do have a house with a semi transparent stain, it can & will ruin that stain ( even the front door stain ) if shot too "hot" or not rinsed immediately. This was a case where the painter wanted all the residual stain removed, though.

also when doing this kind of app I have found TSP to help out because it really preps the wood for an even coat and gets rid of any oil, grease or dirt.

I don't work with it that much, just for rust stains on roofs really or if I have cedar roofs or decks or siding but they aren't too common...
But first of all you want to be real real careful because this is strong acid so protect yourself. If you have worked with it then you know how it fizzes and gets hot so don't allow it to come in contact with anything but the stuff your cleaning, like wood or concrete. This is a seriously dangerous chem too so don't take it lightly just because you work with it a lot and you can only mix with water in a super clean sprayer that is free of all other chems just like you would with 12.5% SH because if not you will have big trouble..

Anyway mix about 1 1/2 to 2 cups of Oxalic acid to 1 gallon H20 for a strong larger job and about a half a cup per gallon for a few rust stains. Only H20 in a crystal clean pump sprayer!!

It has that distinct "I'm gonna melt right through your skin, acid" smell to it. So agiain wear protection. Make sure you wash down whatever you are treating with clean water 2 or 3 times BEFORE YOU USE THE OX ACID, and the same afterwards.

It definitely is something you do have to play with so in your case your in good shape. Every wood will act a little different too. I always put about a cup in and 1 gallon of H20 and mix her up and start from there, that way you can still dilute if necessary. Sometimes that is all you need depending an the tannin of the wood and age and how funked up it is. The main thing you want to use it for is a nutralizer and brightener. Before this you used your tsp or whatever to get all of the grease and oil out.
You "can" downstream this too, but thats not how I roll.
Just make sure you clean out your pump sprayer and if you used and brushes brooms as well.

If you use TSP and bleach on new cedar siding before you paint, the paint won't peel. If you don't it will peel within a year

When you are staining cedar it is a whole different story. Oxalic acid is also called "Wood Bleach" and if used properly it is the right chem for the job most of the time. Especially when dealing with woods that do not have any pitch or resin.