Cleaning Oak Trusses with Oxalic Acid?

[ashthekid]

I’ve been recommended to use Oxalic Acid to clean up my newly installed oak trusses which have all sorts of black marks and water tide marks from where they were stored for so long. 
 

Apparently it’s nasty stuff to deal with and after you’ve used it to treat your oak you must wash it off with soapy water. 
I’ve also read somewhere that it can bleach the oak badly unless you make sure you treat the whole truss evenly. 
 

Is this my only option?

Sand blasting sounds like a waste of time and messy. 

[Temp]

I've reconditioned bunch of oak with just a 30/40 grit sanding disc in a drill. Lots of work (and the divits) add "character" but possible.

[markc]

I wouldn’t use acid, wire brush (with the grain) this could well remove a lot of the marks. You could use some dilute bleach to then make the stains less dark, be careful and don’t apply in drops but rub to soften the edges

[nod]

I’ve used Oxalic to good effect 

Rubber gloves and glasses 

Marvelous stuff

[ashthekid]

I suppose they aren’t too bad but all the videos I see makes me think Oxalic acid will work really well. 

 

 

 

Edited February 27, 2022 by ashthekid

[tonyshouse]

Oxalic acid is a weak acid and is great on oak and ash. brilliant on water stains. 
 

 

[Rishard]

+1 for oxalic acid. Not very nice, but neither are most cleaning products. Wear good protection. It does bleach the wood so you have to cover the whole area. I sand blast all my oak frame jobs as it gives a much nicer Finnish once the job has been exposed to building site conditions. Oxalic gives instant results but trying to make the whole job look uniform is is the tricky bit. Looking at the amount of steel staining and water marks I would look into a local blaster. Make sure you test a sample before they blast your trusses as I’ve seen some blasters turn oak into driftwood! 

[ashthekid]

I’ve arranged for a sand blaster who specialises in oak restoration to do the job at the end of the month. 
I’ll post an updated photo. 

[Temp]

Should look fantastic. I'd suggest putting oil on them soon after as possible. Otherwise make sure no iron or steel is left in contact with them (eg ladders, scaffolding or tools).

 

You could also consider routing the edges before sand blasting but that depends what look you prefer.