Question
I have a large millwork project for storage of sensitive paper documents. The spec is asking for no (or negligible) pH in the wood product. I was told they have used "aspen" before because of these qualities but I can find no documentation on such that supports such a statement. Do any of you know what wood, or if this wood is available to achieve this criteria? I understand it has low pH, but certainly I need more info. Also, what finish is suitable to remain pH free? I believe they used salts in the past but the company that supplied their existing millwork is gone.
Forum Responses
(Architectural Woodworking Forum)
From contributor J:
There's no such thing as 'pH free.' If you want a wood that's neutral then you want it to have a pH of 7. Lower than 7 and you're talking about acids; higher and you're talking about alkali/bases.
The wood and glues in any wood product create an extremely art-hazardous environment. You have to use some type of vapor barrier on the inside surface of the case to prevent this. Some common materials which have proven effective are high and low pressure laminates, aluminum, and acrylic sheets. We often wrap the interior surface of our cases with a product called Marvel Seal, which is sort of an aluminized plastic sheet. Some people iron this down, but we have found that a much easier method is to use 3M transfer tape to hold it down. If this surface is visible, we cover it with Sintra board, which can be coated with an appropriate paint (we have all of ours tested for off-gassing, and allow it to cure for a month before installation of the art) or fabric, also held down with transfer tape.
Actually, one of the easiest materials to use is melamine board. The melamine surface is an effective vapor barrier, which is why HPL also works. If your client has more forgiving standards, here is a list of woods which are considered low in acidity: parana pine, spruce, poplar, elm, African mahogany, walnut, iroko, ramin, and obeche, in descending order of acidity.
