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I have not built allot with redwood, but I have noticed that sometimes there are dark stains in the wood. Looks like where water has sat and the chemicals in the wood migrated to form the stain. Is there a way to get rid of those stains? It seems like they go away on there own, once out in the open and allowed to breath for a few weeks. Thanks for your responses.
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Hi David,
Water stains are common with redwood and red cedar.It doesn't take much for them to form either.Pressure wash it than let it dry.Pressure washing will quickly take out almost anything with out damaging the wood.Don't use to much psi or you may raise some splinters(you can sand a little after to remove them). It's the only way I found to take out stains in wood without sanding(which doesn't always work). I did it to a weathered fence and it brought the wood back to new without using chemicals.The stains may go away on their own if they are not too deep but a good wash evens everything out.I've only worked with red cedar, but I'm sure it's very similar to redwood.
Good luck
Gaby
*Redwood and cedar contain naturally occurring chemical extractives. They derive their durability and weather resistant characteristics from these chemicals. However, these chemicals can dissolve quite easily in water. If water enters redwood from the surface it soaks into the wood, dissolves the chemicals and then is drawn back to the surface as the wood dries. In any event, the extractives are also brought to the surface, resulting in a stain. The stains caused by the extractives can be removed. Mix one cup of REAL tsp, one cup of bleach and one gallon of water. Wash the wood with this solution. Follow this with a solution of four ounces of oxalic acid crystals dissolved in one gallon of warm water. Certainly scale down the proportions if needed. Use a plastic, not metal, bucket to mix the oxalic acid. Wash the wood with this and let dry. When dry rinse with fresh water. Oxalic acid is poisonous and can burn. Wear rubber gloves and goggles. It can kill your landscaping plants as well. Tarp if req'd.There is a way to virtually eliminate extractive bleeding stains, but it requires completely sealing each piece of exterior wood before it is installed. This prevents any water penetration into the wood. Make sure the wood is completely dry before sealing. The California Redwood Association recommends that this practice be followed with any exterior finishing system. As long as you keep your wood "natural" you'll probably get stains. Over time the they may get lighter, but as long as the water soaks the wood and brings the extracs to the surface, your problem will continue.If you can live with the stains, try to do so. I'm not a fan of chemicals that require spacesuits to apply.Regards, Mongo