Hi
I x-jetted the shed with SH and soap, rinse with a garden hose. Then I applied oxalic acid(powder) with a sprayer let it sit for 10min and rinse with garden hose.
I used black propertioner 3-1 with 9,6% SH, 3% hit the wood am I right ?
The wood turn very white when it dried…
Thanks for your help
Sylvain,
Wow, a wood guy from France! Welcome.
For wood, dilute your SH down to ~ 1.5%. Soap content a squirt per gal. of water. Mix, apply, dwell for 5-10 min. and pressure wash off lightly. 3% SH on wood is way too much and is not good for any wood. No need to neutralize with an acid, SH is basically benign on wood but just rinse with a lot of water.
If you are staining, I’d rinse the wood well with a lot of water, then stain when dry.
Hey thanks 
As you can see, I’m really not a wood guy :D, I’m trying to learn.
On this
//youtu.be/h4Bxj4m9AxE
the guy say " 2% on wood and 3% on heavily stained wood"
I tried first 2% SH with a pump sprayer and the stain was stripped as well…
Sylvain,
Oh boy. SH does not strip any wood stain. SH, on its own does not clean. Add some soap and a P’washing, kills mold/mildew and will remove a lot of dirt. Only sodium hydroxide for oil stains, or a really “boosted” hydroxide mix for weathered water based wood stains, will strip off old stain. Otherwise, for the really tough stains, it is magic that us old guys do not readily teach.
Thanks for your help
Before I washed it the shed was like that
Do you think there is something wrong with the stain? When I wet the wood with the garden the run off was brown
@Sylvain, just to clarify, did you use 3% Sodium Hypochlorite (aka chlorine bleach), or Sodium Hydroxide (aka lye or caustic soda)? Because most people on the forum here only use SH to signify bleach. I guess if you wanted to abbreviation sodium hydroxide, you could use the chemical abbreviation NaOH.
You’re right, it’s easy to be confuse. I use SH = Sodium hypochlorite
Hi Sylvain,
I started watching your attached video, but this is a roof guy, not a wood guy. Tile, asphalt shingles, aside from cedar shakes, is not wood. Don’t know if he addressed wood shakes, but I was not going to view 2 hrs. to find out. We do not do roofs, aside from cedar shake gazebos. Have cleaned and stained plenty of those.
Bottom line, sodium hypochlorite (SH) kills, it does not “clean”. Add in some soap, and a SH - soap mix will both kill and clean. In my experience, any mix over 2% SH is harmful to exterior wood.
Stripping wood means emulsifying the old stain, and washing off. SH - soap does not emulsify. Sodium hydroxide does for oil stains, and very weathered certain water based stains. It must be followed up by an acid, typically oxalic or citric acid, to neutralize the high pH of the caustic stripper and brighten the wood.
If you applied 3% SH to that wood, and a garden hose rinse removed the old stain, it was extremely weathered. And your 3rd pic of the shaded side, indicates more intact stain the the SH did not remove. The job is not “stripped”.
Being curious, did a search on Gargenville, France. Beautiful area and country. Spent a few weeks in France years ago, and had a hard time leaving. I’m jealous!
Keep at it, exterior wood can be a puzzle just starting out. More an art learned by experience. It is not “pressure washing”.
Thanks Rick,
Next time I’ll do it better, I’m lucky that is not a job for a customer.
Do you have any recommendation on what type of wood stainer I should use ?
The grass is always greener on the other side of the fence. I want to immigrate to the US, I just bought a house in Indianapolis in April.
Sylvain,
I have no clue as to what exterior wood stains are available in France. If the EU allows oil stains that is good. Stay away from water based stains if possible, for multiple reasons, mostly maintenance.
For an entrepreneur, the US offers opportunity. Work hard and smart, keep a fair amount of profit. In today’s world, for a small business, it is still the “land of opportunity”. But it is competitive, tough, and takes a lot of time, moxie, and effort.
I and many Americans, have a romantic vision of provincial France. Slower, more reflective and intimate way of life.
I’m getting older, so disregard the sentiment.
I happened to have read this thread last night and went with using 1.5% SH Sylvain recommends on wood plus soap on a grayed out deck me and my dad built years ago with no stain And it came out pretty good. I did use a concentrated inexpensive brightner but didn’t seem to do anything I don’t think. The deck looked clean without the bright white I’ve experienced but still can tell it was done with SH to me but the customer really likes it. When wet it had that bright look we were hoping stayed.
Sent from my iPhone using Pressure Washing Resource
For unstained grayed out older raw wood, we generally use a sodium percarbonate based wood cleaner. If there is mold/mildew present, we’ll prewash with a 1.5% SH mix before hand. Follow up with an acid wash, and the coloring of the wood when dry is more natural.
SH is used to kill. On maintenance jobs, where we are just adding additional stain, a SH mix works well as it is not aggressive in removing existing pigment, resins or oil in the wood. And no need for an acid wash.
