How can I take linseed oil off wood that has dried sticky? It tried thinner, denatured alcohol, nothing works.
In addition to the good comments already made, I'll add that in order to remove cured drying oil, you will have to mechanically, not chemically, remove them. I am thinking a fine steel or brass wool, or maybe a scrubby pad, dampened with oil.
Unless it's unsightly though, I'd just leave it. It will slowly cure. It will never be hard, but it won't be gummy either.
Have been reconditioning axe handles, tools, outdoor furniture and wooden ladders as a hobby for many years. Linseed oil comes in two varieties where I live - raw and boiled. Old dry timber responds best by painting with 60:40 mix of Raw linseed oil and turpentine (turps). On an old ladder, you can see the thinned oil disappear into the wooden rungs and stringers straight away. Repeat until it leaves a thin residue on the surface, leave it overnight then do it again. This gets oil right into the timber pretty quickly. For follow-up - maybe after 6 months or a year, use 70:30 Raw to turps mix - this makes the wood feel soft to touch - great on axe handles, outdoor seats etc but not so important for ladders. If you want a nice shiny surface, use 70:30 BOILED linseed oil and turps. Sinks in without leaving a sticky scum on the surface, and it can be polished by just rubbing it with an old cotton singlet. Keep the left-over mixes in a tightly sealed glass jar and they won't go off. Note that 100% raw linseed oil on wooden ladder rungs is dangerous as it leaves a slimy residue on the surface that never dries, and which is only partially rubbed off by the occasional falling human.
I've used mineral spirits in the past to do this. Depending on how gummy things are (the earlier you do this, the better), you may need to scrub a bit, but given time it should come off.
In the future, you may want to dilute your linseed oil prior to applying - I find this makes things easier. (Personally I use linseed oil / polyurethane / mineral spirits in a 1:1:2 ratio, but you could leave the poly out and just go 1:1 linseed oil / mineral spirits for a similar result). The thinner solution helps you to not put it on too thick, and (may be anecdotal but it seems to work for me) helps to penetrate deeper into the wood.
I accidentally left some danish oil on a piece once (a hectic day/mind slip) over a weekend. I just applied some more oil to a cloth and gave it a good rub and it worked a charm. There was a lot of oil on the cloth when I was done which I used to oil a few small pieces I'd lying around that I'd never coated. Waste not want not and all that.