Considering Oil for Deck

The immutable truth of exterior finishes is that the greater the opacity, the greater the longevity.

I suspect that oil would weather quickly, and need frequent renewal, probably every year, or two at most.  I didn't readily see how labor-intensive that renewal process is.

Jason

raw (and high quality) tung oil is $33 a gallon from jedwards. It would take it a while to dry, but it's close to waterproof when you're done - very close, and would effectively be in the wood, and you could buy it pretty much forever. i'm sure there are a lot of explanations from these euro and other oil type or modified oil type finishes touting why they cost that sometimes per quart (or more), but I can't grasp the value proposition. 

Jason is right, though, for a good reason - finishes that dry by bonds like drying oils do can be cured by UV light. The same light that causes the curing or linking of molecules to harden eventually breaks the bonds and degrades the finish so that it loses flexibility and harden and cracks or glazes. 

I've got tung in direct sunlight pigmented on some metal posts now for two years - the paint that I painted on the same posts has started flaking. The tung on the metal posts and the wooden extension above, it's *in* the finish. How long it will last, I don't know, but the outdoor enamel paint (which I knew wouldn't last or adhere correctly) started failing in the first year. 

I don't think you'll find many outdoor oils that guarantee they will hold up without pigmentation, and if they say they do, I'd read what they claim carefully and see what their warranty is. Refined linseed oil is also an option, but not the stuff you'll see on the shelf at home depot. The refined linseed will have a lot of the junk that causes it to darken faster and feed fungus removed. I'd guess all of the oils will still darken over time either the oil itself or the wood under it. 

I have no deck, but had a rail and tried spar urethane. It's junk. My neighbor has a huge deck and tried a couple of years to put an oil type penetrating clear on the deck and realized it only looked good if he did it every year. About a decade ago, he sprayed paint on it and it's been a lot less maintenance, but paint isn't failsafe - it'll hide water ingress at joints and you'll find out the wood is rotted when it falls apart at the joints. he's had to replace some parts of the deck, but it's still been less maintenance than taking a day or two man days every year to put clear on it, and probably has been cheaper. 

I can't vouch for legitimate oil vs. the "water seal" type cheap finishes. Those look to me to be mostly solvent that flashes away and they don't often tell you anything useful about what's left behind as it's a "trade secret".

Added later 13 min 06 s:

I checked the product info sheet for the outdoor version at the link you sent. It's modified linseed oil and possibly with some resin, base oils, and it mentions isoaliphatic components (not sure, but that might be solvent). 

10 liters of the stuff is $540 (in US terms - $205-ish a gallon, presumably plus sales tax!!)

Barf. 

The info sheet says once a year on a deck for the first three to five years, and it has non lead dryers in it (no kidding, so does everything else in the US). 

reapplying once a year for the first three to five years would have me looking quickly at just pigmenting tung oil and if you don't want to wait a long time for it to dry, 1% klean strip japan dryer or another brand that's the same thing (zinc, manganese, and probably cobalt salts), and you're making your own. I find that 1% dryer of that type in tung results in mostly dry finish if applied and wiped off, but soaked in - in a day. Lightfast pigments in the finest particle size would be next on my list to try with it. I would guess that you would be applying finish on wood with pigment using artist grade micronized pigments for about $50 a gallon, and you'd own the process. Raw tung is a stock sold in bulk - it's not going away. Pigments won't go away. We'll see about drying elements that are in japan dryer - they are getting less widely available at the retail level). 

If esterified linseed oil was better for durability than tung, I'd be surprised. 

Watching my neighbor faff with his deck makes this hypothetical for me. I dug up the ground and laid a paver patio, instead. Every five years or so I refresh the polymerized sand in the joints.

Peter Martin wrote:

Opinions?
https://www.youtube.com/watch?v=gncCfLg30b8

it'll kill everything that tries to get in wood or cause rot alright. I didn't listen through the video other than to find what it was, but it's unhealthy for human contact. Creosote is pretty effective on wood, too - spent some of my youth brushing it thinned with diesel fuel on horse fences. Fortunately not too much of my youth doing that!

https://www.gefislands.org/HazardousProducts/Used-Oils
" Used oil can cause chronic and acute damage to human health. It is carcinogenic, genotoxic and fetotoxic. Exposure to used oil can impact immunological and reproductive systems and damage kidneys, liver, heart, lungs and the nervous system. Impacts on fauna include toxic contamination, impaired reproduction, damaged intestinal tracts and reduced fur insulation."

My relatives were farmers. I have one remaining relative who still is one, but my parents' generation as farming got bigger and was still combination large but a lot of hard manual labor at high speed, went to college and got out of it. 

the article you put together with the help of AI reminds me of my childhood. Largest farm in the family back then (35 years ago) was 700 acres, and with that much acreage at the time, there was a lot of oil changing on diesel tractors and a lot of used oil. It was just kept. I remember a relative of mine having some left over after in the bottom of a pan dribbling it along the edge of one of his buildings. If you dribble used motor oil on the ground, nothing grows where the ground meets the building and if you have a lot of buildings and low margins, that kind of labor reduction is important. 

It also reminds me that if you live in the city, you'll lean against fences and posts. Back then, we never would. if someone used motor oil on posts, and you leaned against them, you'd get ruined clothes. if you touched the posts, your hands would stink. I think even back then, it wasn't legal to use used oil like that, but in a situation where there's not a lot of contact, if the contents don't run off (can that really be controlled?), it does work well. 

An enterprising person with a couple of flea market stainless pots, a cheap double sealed burner off of ebay and a thermocouple can make limed tung and rosin varnish for about $35 a gallon or something, I think. I could be off by $10 somewhere with that, but you can do a lot to manipulate it, making it seem more like an oil finish or more like a top clear finish. That'd be my choice here. Since that's not reasonable for the average person to do it, raw tung oil would come up after that, which is $33 a gallon at jedwards and not gummy or thick like the polymerized oil. If it's thinned further, it can really penetrate. 

I'm genuinely curious what some kind of esterified oil product for $200 will do. it will probably dry faster, darken less, and maybe it has an antifungal additive or something -but if you find out what that is, you can probably just add it to tung oil. Since starting to make varnish, and seeing how good some of the relatively simple varnishes are, and buying the oils that are put in smaller bottles and then jacked up in price, I'm kind of surprised there isn't more curiosity about making finishes above and beyond mixing shellac. 

lastly, what would be the difference in life span on a deck, for example, for Tung oil (pigmented or not) vs. the commercial products? There must be some benefit to buying the commercial stuff, but until I manage to hide a piece of wood for a few years outside to see how it holds up (ok, that won't happen), I can't really answer that question. 

Side comment - I see waterlox sells pure tung oil for decks, and they describe use and care. It's an in the wood finish like any other oil, and not on it, so when it looks worn, you refresh it, according to them. 
and for the privilege of buying something branded, you pay $109 a gallon for it instead of $33.60.  Identical CAS number and composition.

We have a Trex deck. We tend use it mornings and late afternoons when the days are hot and sunny. It can get hot enough to actually burn the feet of barefoot children and dogs.