Applying real tung oil to freshly milled pine?

[Jason Evans]

I'm making some raised beds and using freshly milled pine. I know there are better woods around to use, but a great mill in the area sells pine boards for a great price. I hope to get a few years out the beds. I've seen freshly milled pine last a long time with nothing on it, even close to the ground.

To extend the life of them I was considering using tung oil and citrus solvent to coat them, might add a couple years to them. The cost of the oil and the pine is far below any other wood choices around. I'm pretty familiar with working with tung oil on dried woods and have finished quite a bit with it.

I am looking for opinions on whether or not the tung oil would work on freshly milled pine. I imagine they won't soak up much, but it seems like the tung oil would at least create a pretty good film on the boards, especially if applied thick, as in less citrus solvent or close to none. But maybe the moisture of the wood will cause the tung oil to not stick at all. Anyway, any opinions welcome. Thanks

[Lisa Starr]

Jason, I know of a wood turner that uses Tung Oil on green wood to prevent cracking while it dries. I'm not sure if he used any solvent though. I know he said it doesn't soak in much.

[Doug Garson]

No idea about the tung oil but if you line the raised bed with 6 mil poly so the wood is not in contact with the soil (inside and bottom) you can extend the life of the wood.

[Jason Evans]

Thanks Lisa. I imagine it helps prevent cracking by slowing the dry time. Maybe a slower dry time would be good for raised bed wood, since it would keep the pine oils and all in there longer, possibly providing protection. Maybe.

Seems like it would be better than not using it. But by how much is the question. I wonder if it’s worth the extra cost and time.

[Jason Evans]

No idea about the tung oil but if you line the raised bed with 6 mil poly so the wood is not in contact with the soil (inside and bottom) you can extend the life of the wood.

Thanks Doug. Would probably help. Trying to keep prevent using plastic on these. Once it dries up and breaks into pieces it’s difficult to remove from the soil.

[Doug Garson]

Thanks Doug. Would probably help. Trying to keep prevent using plastic on these. Once it dries up and breaks into pieces it’s difficult to remove from the soil.
I've lined cedar or pt wood with the 6 mil poly and not experienced any of what you described years later when the wood finally had to be replaced. I guess if you want to avoid plastics, you could line with aluminum flashing (I haven't tried it). Assuming you using 1 1/2" or full 2" thick boards they should easily last several years without treatment, just my guess.

[Jason Evans]

Great info Doug, good to hear your experience with plastic. May still go that route.

I really like the idea of aluminum flashing, seems less questionable than plastic. Thanks a lot

[Andrew Seemann]

Thanks Doug. Would probably help. Trying to keep prevent using plastic on these. Once it dries up and breaks into pieces it’s difficult to remove from the soil.

The polyethylene doesn't dry out; it degrades in UV light. It will be fine for a while, then it will start getting brittle, and then suddenly it will break into flakes which then break into smaller and smaller flakes.

Under the soil it should last indefinitely, as long as you don't cut into it. The problem is if it rises above the soil. That is exposed to the light. Construction poly tends to last a little under a year, UV resistant will be rated in years and can go up to around 5 or so years. I'm not sure where you would get multi year UV resistant poly in small sizes though, it typically is used for greenhouse roofs and agriculturally.

[Richard Coers]

I'd question the longevity of a single coat of tung oil in an outdoor application.

[Jason Evans]

The polyethylene doesn't dry out; it degrades in UV light. It will be fine for a while, then it will start getting brittle, and then suddenly it will break into flakes which then break into smaller and smaller flakes.

Under the soil it should last indefinitely, as long as you don't cut into it. The problem is if it rises above the soil. That is exposed to the light. Construction poly tends to last a little under a year, UV resistant will be rated in years and can go up to around 5 or so years. I'm not sure where you would get multi year UV resistant poly in small sizes though, it typically is used for greenhouse roofs and agriculturally.

Thanks Andrew. I appreciate your time. It does seem like it would last for quite a while with the soil covering it. I also wonder about things like the plasticizers like BPA etc. and their effects on the the food with direct soil contact. I'm starting to think I would be better off just letting the wood rot and replace later.

[Jason Evans]

I'd question the longevity of a single coat of tung oil in an outdoor application.

Me too, what about several coats of tung oil? I wonder if it would stick to wet wood or would the water escaping the wood cause the tung oil film to drop off the wood?

There's also a milkpaint product which is mainly tung oil, pine oil and zinc for outdoor wood protection that might be good. I guess the zinc adds uv protection. But the main concern is probably the soil wood contact.

[Alex Zeller]

If the wood is cheap enough I don't think I would do much of anything. So it rots? It'll just make for good soil in a few years. I've used hemlock (since it's easy to get around here) and the sap wood will last 5 years without doing anything. I did use cedar for my wife's raised beds since it's also not hard to get.

[Jason Evans]

If the wood is cheap enough I don't think I would do much of anything. So it rots? It'll just make for good soil in a few years. I've used hemlock (since it's easy to get around here) and the sap wood will last 5 years without doing anything. I did use cedar for my wife's raised beds since it's also not hard to get.

Thanks Alex. I think not doing anything is probably the best route. Time is really valuable for me. Easier to just replace it later or wrap some new wood around the whole thing when it starts to rot.