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I have built a platform bed using 90%+ cedar (all but some quarter round and the legs).

My plan was to use raw, food grade flax / linseed oil to finish it. I like the idea of the raw oil not having chemicals added. Plus, I’ve used this on cedar shelves and love the depth of color it brings to the wood. Since this is an indoor piece and made in cedar, it doesn’t seem to me that there is a need to apply multiple coats to protect it (correct me if I’m wrong on this), so I’m not too worried about drying time - I just want to get one good coat on.

My primary concern is the fact that it takes longer (days to weeks?) to oxidize than boiled linseed oil. If I put the bed on the frame before it fully oxidizes/cures, is there a risk of combustion?

I’m not putting the oil on the slats that the bed sits on, but it would be on the inside of the top layer of trim (about about 3/4” deep). This would be covered by the side of the bed. Thoughts??

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My primary concern is the fact that it takes longer (days to weeks?) to oxidize than boiled linseed oil.

Weeks at least, possibly months. Indoors, if the conditions aren't ideal, it could take a year or more before the overwhelming smell of linseed oil dissipates1.

If I put the bed on the frame before it fully oxidizes/cures, is there a risk of combustion?

The risk of spontaneous combustion from linseed oil (and other drying oils, as well as products made from them including varnish and products like "Danish oil") is from any bundled rags that are wet with them.

If the oil is applied to the wood and then wiped away to nothing, as it's supposed to be, the amount of oil that might come out of the wood into the bed is going to be very small indeed. Enough to cause minor oil staining at worst.

Thoughts??

Since you asked, you don't need to be overly concerned about the 'chemicals' added to most commercial BLOs. I won't sway you if you've made your mind up, but this is of potential value to future readers.

The metallic drying agents added to most versions of BLO are no concern once the finish is on the wood and it has cured2. The primary health risk is to the worker .....just as it is from wood dust, see next point.... and you can easily protect yourself from any contact during application by simply wearing gloves. There's no need to wear a mask of any kind.

In this case what makes the decision not to use a finishing product because of the chemicals it contains a little asymmetrical is there are compounds that are of concern in the wood used. The awesome smell of red cedar is from chemical compounds. And those in red cedar are actually a known irritant.

1 Only possible to generalise here, being a natural product linseed oil varies and it can be surprising just how much variation there is (the colour range alone gives an indication of this).

2 Where they are OK even if used for surfaces that will contact food, which gives a fairly realistic idea of the actual risk they pose from incidental skin contact with wood finished with them.

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  • Thanks for the detailed response. I went with boiled linseed oil to play it safe (after the work to build the furniture, no sense in risking it with a product that could prove problematic). The odor and the absorbtion/drying time has been very similar to the raw linseed oil I used for shelves - sounds like that was likely circumstantial / luck of the draw though.
    – Adam
    Commented Jan 13, 2019 at 5:11
  • I think that was a good call as you'll get more reliable results from BLO. The initial 'drying' time for oils is always hard to judge, because unless there was some liquid oil left on the surface somewhere (always a bad thing) how to tell from the wood? The full curing period for BLO (and most varnishes, and products that contain varnish incidentally) is invariably given as "about a month" to allow a safety margin for different conditions, but essentially full cure can be determined fairly accurately by whether there is any odour when you smell it with your nose right near the surface. [contd]
    – Graphus
    Commented Jan 13, 2019 at 6:45
  • This is where you'll really notice the slow curing of raw oils, because the smell can sometimes linger for more than four weeks. The last time I used a raw linseed oil myself (for an exterior project, I'd never use it for something intended for indoors as there's no point) I could still smell the oil at week six and it may have finally petered out sometime after month two but life got in the way and I forgot to continue to check.
    – Graphus
    Commented Jan 13, 2019 at 6:49
  • What led you to use raw oil on your exterior project?
    – Adam
    Commented Jan 14, 2019 at 13:59
  • Raw oil is the oil of choice for exterior use, BLO isn't recommended. This is if you're using oil at all, in fact it's not advised for wetter climates such as the British isles and that's one of the things I was testing for...... and confirmed, black staining (fungal attack) set in before the end of the first year once it was outside in the weather.
    – Graphus
    Commented Jan 15, 2019 at 6:05

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