We had a redwood deck installed some years ago. DW stained it. Within a year or so, it got very dark......almost black, and although not perfectly uniform, uniform enough that it was hard for me to believe that it was mildew, which for some reason, I associate w/ irregular patches.
I removed the blackness by mechanically sanding the deck w/ a small power sander and also some time-consuming hand-sanding in some deeper grooves that we had at some point created w/ our first experience with a power washer.
Right or wrong.....I did not believe at that time that the blackness was mildew (too uniform) or natural graying of the redwood (too black, too fast ). I instead thought it was something about the stain.
For the next go-arounds, I instead used Thompson Water Seal which seemed to be much better. It did not turn "instantly" black like that first stain but the process seemed to be a lot more gradual. After some number of years of rejuvenating w/ more of the same, the black stage again has arrived.
Although I rejected chemical treatments the first time around, I'm considering it this time.
My issue: what is the blackness and what treatment makes sense?
Chlorine bleaches are not recommended.
O2 cleaners are recommended for mildew and natural graying.
If I don't think it's mildew , is it reasonable to believe it would work.
Oxalic acid cleaners are recommended for redwood tanins but
they talk about these as being orangish...or at least something other than black. Is it reasonable to believe this would work.
I don't mind doing the power sanding but the blackness in the grooves from the earlier power washing is the part I don't relish doing again.......the grooves are deep enough that I wouldn't want to level the whole deck.
Suggestions welcome.
edit to add: DW went out and bought a power washer over objections from my still-alive (I think) body so now there are patches of bare wood and blackness. Will the chemical cleaners do harm to the bare wood?
I removed the blackness by mechanically sanding the deck w/ a small power sander and also some time-consuming hand-sanding in some deeper grooves that we had at some point created w/ our first experience with a power washer.
Right or wrong.....I did not believe at that time that the blackness was mildew (too uniform) or natural graying of the redwood (too black, too fast ). I instead thought it was something about the stain.
For the next go-arounds, I instead used Thompson Water Seal which seemed to be much better. It did not turn "instantly" black like that first stain but the process seemed to be a lot more gradual. After some number of years of rejuvenating w/ more of the same, the black stage again has arrived.
Although I rejected chemical treatments the first time around, I'm considering it this time.
My issue: what is the blackness and what treatment makes sense?
Chlorine bleaches are not recommended.
O2 cleaners are recommended for mildew and natural graying.
If I don't think it's mildew , is it reasonable to believe it would work.
Oxalic acid cleaners are recommended for redwood tanins but
they talk about these as being orangish...or at least something other than black. Is it reasonable to believe this would work.
I don't mind doing the power sanding but the blackness in the grooves from the earlier power washing is the part I don't relish doing again.......the grooves are deep enough that I wouldn't want to level the whole deck.
Suggestions welcome.
edit to add: DW went out and bought a power washer over objections from my still-alive (I think) body so now there are patches of bare wood and blackness. Will the chemical cleaners do harm to the bare wood?