On a recent job, we had some dark satins in redwood appear after the rain.

When redwood gets wet, it can sometimes have dark spots turn up.

Since the frame of the gate was steel, we thought perhaps the dark spots may have been the result of oxidation (rust) from shards of metal perhaps blown onto the wood from grinding during steelwork.

Previous experience using cleaning solutions were only with hardwood with species such as ipe or red mnagaris.

In fact, we just went through a similar dilemma after installing garapa wood on a garage door in Bel Air.

The rain, especially heavy rain for sustained periods, can really pressure-test any outdoor setting.

To restore the wood and refinish, we stick with Penofin brand's recommended three step process: strip, clean, and brighten.

This is a water-based method which avoids both sanding and power-washing.

However, redwood responds differently to this method. Redwood does not have the density of ipe, red mangaris, or garapa. It can be damaged by power washing so this is definitely not a course of action.

After much experimentation, we ended up needing to sand it. This was the only sure way to eliminate the spots without damaging the wood.

Conversely, with a hardwood like ipe, we never found it necessary to sand it after the three-step process.

The reason why redwood is selected is price, sustainability, and color variation which has a naturalistic tone that evokes a sense of unity with nature.