Sealing raised bed made from treated wood

Asked June 2, 2020, 10:44 AM EDT

Hello, we recently constructed a raised bed out of treated wood (micronized copper azole). From HGIC info (https://extension.umd.edu/hgic/topics/materials-building-raised-beds) it seems this is minimal risk for food gardening, but we are still interested in sealing the wood, both for looks (stain), and to prevent things from the wood getting to the food. We have some stain left over from other non-gardening things we are interested in applying to the bed. Is it safe? It is Thompsons WaterSeal Timber oil (https://www.thompsonswaterseal.com/waterproofing-products/penetrating-timber-oil) I don't see much info on what is actually in it on the can or the web page. Is that Timber oil safe to use all over? If not all over, is it safe to use on the outside? I understand linseed oil is safe to use to treat food gardning wood, so we could treat with linseed oil where soil touches the wood, and colored timber oil on the more visible parts. Thanks!

Baltimore County Maryland

1 Response

Your leftover sealant may be safe to use, but we cannot be certain. As you suggest, you can certainly use it on the outer surfaces only, and use the linseed oil on the interior. Similarly, you could use linseed oil exclusively on all surfaces. Any other wood preservative products labeled as food-safe would be fine to use as well. If uncertain as to what product alternatives exist, you could seek out and try asking area woodworking groups, as they likely have members crafting wooden items meant to come into contact with food (serving spoons, salad bowls, etc.).

Miri