Heh heh, it's a big read, isn't it. Right at the very end is a link to Dr Brian Blood's recommendations on care of Dolmetsch Recorders. (Brian is a son-in-law of the late Carl Dolmetsch, and is now managing director of the firm. I never met Carl, but caught a glimpse of him when visiting the factory at Haslemere in 1974. The staff seemed very much in awe of him.)
In the care notes, Brian mentions:
Dense hardwoods like grenadilla [posh term for African Blackwood]
generally require very little additional oil, but porous woods like boxwood and even softer fruit-woods like cherry or pear as well as the ubiquitous maple, if not already treated in some other way (see below for further comments on this), will benefit from a regular treatment of the inside of the acoustic bore with a good well-drying oil.
And later:
Lighter oils (mineral or walnut) are to be strongly recommended because they dry more quickly.
Now, clearly, mineral oils do not dry. But perhaps he means they soak in more quickly?
But then he goes on to say (near the end):
"Bore oil" that you buy at the local music store in little bottles is an entirely different
story. It's often mineral oil or petroleum oil and has a number of interesting
characteristics. First, it's biologically incompatible (except for special bacteria genetically
engineered to clean up oil spills) so it does not go rancid. Second, it dries much slower,
and is much more immune to natural and man-made detergents, so it stays in the bore
much longer. Third, it's a very effective vapour barrier. But it's not as compatible with
wood as the nut oils, and it's difficult to clean out of the bore (keeps building up in waxy
layers). Personally, I avoid it. Clarinet and oboe players swear by this kind of oil, but
then again, these are the same people who take Grenadilla (African Blackwood) which is
absolutely beautiful with long streaks of browns, reds, and blacks, and stain it jet black
(and lacquer the outside of the instrument) so it looks like plastic.
So, perhaps a little oddly, he at first seems to promote mineral oils because they don't go rancid, stays in the bore longer and forms a "very effective vapour barrier". But he seems confused on whether they dry or not. Hmmm.
Interestingly, the preceding article seems to be reasonably positive about mineral oils. Most of the modern commercial instrument making companies promote or sell mineral oil. I know it doesn't fit easily with our preconceptions....