Black Spotting on Wood Door & Floor

[i_am_chris]

Hi, we are wondering what this spotting might be. Its happening on both the doors delivered by our yurt manufacturer and the floor we sealed ourselves.

Pictures and more details here: http://www.yippee.cc/woodspots.shtml

Thoughts?

[Don_P]

It looks like a metal stain.
Could be mildew but the trail off it looks more like metal.

A deck brightener containing oxalic acid might work .
You have insufficient finish protecting the wood.

[i_am_chris]

We obtained oxalic acid and it does appear to be working to remove the stains. Thanks for the tip. We've noticed the floor has a bit of a yellowish taint to it. The manufacturer suggested rinsing with baking soda & water in addition to clean water. On the web I found two suggestions for light sanding after the floor had dried, though the manufacturer does not suggest this. The floor had already been sanded smooth before we started spot-removal. Would the sanding be to remove the yellowing or just a generally good thing to do before applying finish?

[Don_P]

Just a good idea, especially after wetting with anything that can be grain raising.
We've spent the past 2 days sanding an oak timberframe entry, boy was that a job. We used LandArk finish. It might be of interest to you. It was my first time with it. I'll try to keep an eye on how it holds up.

[i_am_chris]

Any idea why the floor might've turned yellowish?

[i_am_chris]

The oxalic acid worked great. It was a bit of work, and Cassandra let it sit a bit longer on some of the darker stains, but as a whole this was the perfect solution. Additionally, oxalic acid seems to be more "natural" in the sense that it is not some complex mix of nasty stuff, just the acid itself. We found Savogran brand at a local hdwe store after reading the MSDS on-line. Cass was safe for using it. Thanks again for the tip. We've got two coats of finish down and the floor is looking excellent!