The second square foot bed I built I made out of 2x12 pine instead of 2x6. This time I sanded the wood and treated it with boiled linseed oil for a longer lasting box. Unfortunately I had the pieces finished before I read the warning on the back of the linseed oil. Boiled linseed oil contains toxic metal drying agents and is not recommended for use on children's toys or food prep items. Hardly what I want to grow food on, but since I had it all ready to go, I installed it anyhow and Nikki uses it for cut flowers.