Carl Hansen & Son Chairs? Refinishing Options  

I could tell you what I would do but usualy @tktoo2 is the one to be trusted when it comes to woodworking and finishes. Let's see what he recommends. 

@andrewhess, @herringbone, Sorry for tardy reply. I've been blissfully away without internet connectivity.

From the photos and description, my guess is that the bleaching and dark streaks deep in the wood grain may have been caused by fungal infestation resulting from long-term exposure to a dark, high-humidity environment. Unfortunately, dried linseed oil (primary ingredient in almost all commonly available "Danish" or "teak" oil finishes) makes a good meal for various molds or mildews. As do certain wood glues, btw, so check those joints.

I've only done work on two pieces that seemed to suffer from a similar condition with not the greatest results, I'm sorry to report. But I would probably try treatments in this order: Stripper, oxalic acid (maybe 2 or 3 rounds) and, as a last resort,  two-part wood bleach (which I did not try as it is hard to source and seriously toxic). I found regular household laundry bleach too weak to do much of anything at all.

As for oil furniture finishes, most any product should be fine. I buy Watco in the smallest size from high-volume retailers to assure freshness, label the container with the date opened and dispose of any leftover more than 2-years-old.

That's all I got. Good chairs worth saving. Bon chance!

@tktoo2, @herringbone I'm replying with a new account (can't seem to get my original account un-banned!):

Fungal infestation!?! Ahh! Here are some new pics after I sanded to 150. What do you think? Do I try some oxalic acid, or do you think an oil finish will look okay at this point?

Second pic.

@andrewhess2, Color looks fairly even in your photo despite remaining dark streaks. That's pretty much as far as I was able to get even after 2 oxalic acid treatments. YMMV. If you decide it's worth a try, oxalic acid is is inexpensive and available at most good paint stores, but the water in the solution will raise the grain meaning you'd need to re-sand before oiling.

If it were me, I'd go ahead and apply oil and consider the dark streaks to be honest evidence of age (patina!). Oiled white oak will darken somewhat over time and exposure to UV (and other environmental elements) and, hopefully, will help to even out overall appearance. Besides, what's the point of owning something old if it's been tarted up to look brand new?

Whatever you do, please post results and welcome to the Forum!

Oh, the banned thing. Happens to the best of us. It's a bug. Try logging out and logging back in. That seems to work for me.

I like your answer! Time to reach for the oil. And you mentioned the joints -- they are solid.

I'll def post results.