From my reading the right approach is:
- Wet down timber - aide penetration, prevent drying out
- Spray with warm/hot sodium percarbonate solution - soften dead surface materials
- Wait 15-30 minutes
- Rinse off/scrub off/gently blast off
- Spray with oxalic acid solution - neutralise high PH from hydrogen peroxide and bring out colour
- Wait 10 minutes
- Rinse off/scrub off/gently blast off
- Allow to dry
- Oil or oil stain the timber, two coats, 6-24 hours apart - bring out colour and protect from water
The other thing is, the stuff on some of it is soft enough to scrape off with your finger nails, so I might give it a gentle blast to get the loose stuff off first.
I already had the oxalic acid, so last night I ordered 5kg of sodium percarbonate to go with it. Yet to select an oil/stain or buy that, however it's coming soon!
Ideally I need to have all the wood treated to the end of the process and loaded on my trailer by Friday night this coming week.
So I had better go and collect it later today or tomorrow evening, then! :-/
Don't have a good strategy in mind for cleaning all four faces of the timber efficiently, either.
Was thinking of just laying them on the ground tightly spaced and doing one side/face at a time in sets, then turning and repeat.
Goal is to prepare the timber for use on a small deck for a small 10sqm cabin my wife and I are going to build, and then get it stored on site ready for use.
Initial requirement is to have it out of my sister's garage by the end of August, so we're well on target for that, at least.
The timber: https://twitter.com/FredCookeNZ/status/ ... 1843072000
The quality varies from piece to piece and end to end, some parts have clearly been sheltered, and other parts clearly constantly wet and deteriorated.
Hard to tell while it's like it is, should be obvious once the water blaster has had its way - any bits too far gone can be trimmed/discarded.
Thoughts welcome.