I was watching “Ask This Old House” with my grandchildren yesterday and was surprised to see them building a raised bed for a disabled individual out of what looked like pressure treated lumber. To my surprise, the lumber was treated but not with the usual toxic chemicals. Rather, it was treated with sodium silicate (a mixture of sand and sodium bicarbonate) which is glass. The high pressure and temperature process infuses the wood fibers with a protective glass coating and makes the lumber impervious to rot. The product is fairly new on the market is called “TimberSil”. If your thinking about making a raised bed, this new product may be answer to more expensive borders like stone or block.