Is Oxalic Acid the best stuff for removing black streaks, water stains and uneven tones in wood that’s been exposed to the weather for a while.
The wood ranges from pine to oak and will get a clear finish when prepped.
Kevin Halliburton
“The Greek comic poets, also, divided their plays into parts by introducing a choral song, … they relived the actor’s speeches by such intermissions.” Vitruvious, (Book V)
Replies
Oxalic acid is probably the best all-around. Chlorine bleach will work better in some cases but is a lot harsher, both on the wood and on your skin.
Anything you use will cause some "weathering" of the wood, making it rougher.
Be careful to keep the oxalic acid away from any anodized aluminum (which is to say, most forms of aluminum trim), as it de-anodizes it.
Thanks - It will get sanded after bleaching too so that should knock any raised grain down but a little "rougher"-ness of the wood might actually be a nice touch on this one.
Part two of the question is, Anyone have a good source for Oxalic Acid? I found a fireworks chemical supplier that had it for $5 or $6 a pound but it's an internet company I know nothing about.Kevin Halliburton
"The Greek comic poets, also, divided their plays into parts by introducing a choral song, ... they relived the actor's speeches by such intermissions." Vitruvious, (Book V)
About 1 part acid to 3 parts warm water sound right?Kevin Halliburton
"The Greek comic poets, also, divided their plays into parts by introducing a choral song, ... they relived the actor's speeches by such intermissions." Vitruvious, (Book V)
TRy a hardware store or paint store.
Yeah, a hardware or paint store. Just be careful and read the labels -- lots of different things are called "wood bleach".
You can also find it sold in a liquid form, labeled "deck cleaner" -- usually with a few other chemicals mixed in that may or may not cause problems. Again, read the labels.
I found some on the shelf at the drugstore (walgreens) - - very useful for looking like a genious - - had some discolored oak flooring from the tile guys - it looked bad! - - mixed up a oxalic acid slurry and attacked the area with a brush, took 2-3 applications over a couple of hours - stain gone - did not look like a genious when I neutralized it with baking soda and discolored it again - fortunately caught on real quick and brushed on a little more acid, wiped off, let dry and finished..."there's enough for everyone"
I would try neutralizing the oxalic acid with vinegar next time - shouldn't leave a stain behind
Since both oxalic acid and vinegar are acids, I don't see how vinegar could neutralize the oxalic--I'd use some bicarbonate of soda (baking soda). It will foam, but that's okay. I think I read, probably here, that it's not necessary to neutralize the oxalic--just rinse with clear water. Maybe ask on Knots too.
Yeah, just rinse well, or, better, wash with a little detergent. The oxalic sort of dissolves some of the weathered wood, leaving a sort of gel that needs to be washed off.
Ok, the Oxalic acid did a respectable job but not quite respectable enough. There are several dark gray ghost lines where the water ran between the seams on the upstairs decking and stained the exposed ceiling joists.
Now what? Bleach?
Kevin Halliburton
"The Greek comic poets, also, divided their plays into parts by introducing a choral song, ... they relived the actor's speeches by such intermissions." Vitruvious, (Book V)
Household bleach doesn't work really well in my experience. Oxalic acid is the easiest and best for removing rust or other stains. The two-part bleaches (hydrogen peroxide and sodium hydroxide) work best for removing the natural color of the wood. It isn't so good for spot repairs. They all have limits and sometimes won't remove all of the stain. Bleach it again or try the peroxide stuff. There's always sandpaper.
Now what?
I vote for more acid...keep workin' it, scrubbing, whatever it takes to get the acid to the area - sop it up, scrub it in, let set, repeat as necessary to keep the area sopped - - it's an imperfect world..."there's enough for everyone"
I'm on the fourth scrubbed in application and I didn't notice much of a change between the second and third. This is an oxalic acid "deck cleaner" mixed at max strength but it was probably a lot weaker than a straight acid/water mix to start with. I can't find the acid crystals locally anywhere.
The sandpaper isn't cleaning out the black spots in the pores either. That 4" Rockwell belt sander with an 80 grit belt seems to do the trick but it scoots me and my scaffolding over a few feet every time I kick it on. <G> I might try nipping away the surface layer with a hand plane but I don't want to get too carried away grinding down the thickness of my floor/ceiling joists.
I will hit it with acid a few more times but eventually I may just have to go with a solid body stain or bolt my scaffolding to the slab while I'm belt sanding. Thankfully I've only got about 24 of these critters to tackle.
Kevin Halliburton
"The Greek comic poets, also, divided their plays into parts by introducing a choral song, ... they relived the actor's speeches by such intermissions." Vitruvious, (Book V)
Kevin,
This summer, my wife and I had to remove staining from a log house we are building. We got an Oxalic/hydrochloric acid mix at Sherwin Williams called X-180 and I believe it is available at most paint suppliers. It is a concentrate and you mix 1 part cleaner with 4 parts water and apply with a garden sprayer. After sitting 15 or 20 minutes, we pressure washed the house and it turned out great. You can see pictures of the house with some of the logs partially cleaned at http://www.huskylogwork.com/h_harmon.php.
Steve
I was gonna say try muriatic acid but didn't want a bunch of people jumping on my ####. aka hydrochloric (sp)
I believe that as long as you either rinse or nuetralize it it will be ok, taking into consideration other nearby building materials and vegetation.
I've used it very successfully on darkened flooring from urine.........the floor guy gasped but couldn't believe the results.
You might want to consider that you have the wood so soaked with water currently, that it may be unable to accept any more liquid.
Eric
Every once in a while, something goes right!
Try a log home supply....I used to get the oxalic acid crystals from Schoeder Log Home Supply.... a product called Renewzit.
Bleach is to wood stain removal like Thompson's Water Seal is to deck finishing. (IMO).
I' used straight bleach on cedar with good success when applying four or five times
i've also used oxaylic acid crystals with decent success - more application -- the brighter it gets.
MY best results were with the square vibrating floor sanders and the heaviest paper.
(16" square?) that you can rent... that ground down everything including the stainless screws that weren't set deep enough before they snapped off. probably ground down a 1/8" or so.
I'd try the oxalic/hydrocloric acid combo someone else mentioned, but I had a little luck once, after nothing seemed to work, with using strong ammonia to get a water stain out. It really shouldn't work, but it seemed to help. May want to test in a spot that won't be seen first if you decise to try it. (Also, if you've previously used acids, since ammonia is a base, there may be a reaction (like foaming) as the ammonia first neutralizes the acid, then I'd try more ammonia and see if it helps.)