What's sold today as Danish oil is usually some variation on an oil/varnish blend which you can easily make your own version(s) of. As I recently read it called on some blog somewhere, "oil from another country" :lol:
Two simple variations to make are one for warmer weather and a thinner one for colder weather.
Cold-weather version:
2 or 3 parts polyurethane varnish
1 part oil
3 parts white spirit
Warm-weather version:
1 part polyurethane varnish
1 part oil
1 part white spirit
I use boiled linseed oil for this type of thing, you can substitute tung oil it if you prefer it to BLO but it won't give you any benefit in the short term. And eventually the colour will end up the about the same as if you'd used linseed so you might as well get used to it now
DIY teak oil:
1 part alkyd or polyurethane or phenolic varnish
1 part raw linseed oil (don't substitute BLO)
3 or more parts white spirit
or
1 part spar varnish
3 or more parts white spirit
You blend in as much spirit as needed to get to the right watery consistency. This is an application where you may see a benefit to substituting tung oil for the raw linseed oil.
Bog-standard paste wax for rust prevention:
melted candle wax
white spirit
Approximately equal volumes of wax and spirit. You melt the wax, see what volume it makes up and pour in the same amount of spirits. The liquid will cloud when you pour in the cold spirit to the molten wax, stir and heat until it's clear again then decant into an airtight container and wait for it to solidify before use.
Best to use a double boiler for safety reasons when doing this, especially if you have gas rings.
Paste wax for wood finishing:
some combination of waxes
white spirit
Finishing wax is made in the same way as above but substitute some combination of harder waxes to make the finish more durable. Beeswax + 15-25% carnauba works well and has been used for generations. Many today are using versions of microcrystalline wax (with or without other waxes) which can be very hard and is often much cheaper than beeswax.
Standard mix is again 1:1 wax and white spirit. If you prefer a softer wax that's easier to apply don't use softer waxes, blend them with more white spirit. If you prefer a stiffer mix that has to be worked into the surface with harder rubbing use less white spirit.
Oil/wax finish for tool handles:
2 parts melted wax
2 parts walnut oil, raw linseed oil or sunflower oil
1 part white spirit
This gives a nice grippy feel to tool handles. I don't like this for anything else as it's not a durable finish and gets grubby far too easily. Plus it's just dull.
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You can substitute turpentine for white spirit in any of the above if you prefer the smell, it makes zero difference to the result. Despite what some sources claim there is no synergistic effect because turps is from a natural source and not distilled from crude oil. Only the woodworker cares, the wood doesn't notice.
If you don't like the strong odour of turpentine or standard white spirit, or would like to make a finish that is slightly less hazardous to handle, you can use low-odour solvent or OMS in most of the above. But this may cause an issue with certain resins so you'll need to experiment with anything that has a varnish component.