microcord

Decades ago, I bought a Selle Italia Turbo Special:

(Maybe it was named after Turbo Pascal; this was big around that time.) The example in the photo (which I purloined from somebody's Pinterest) is more pristine than mine has been in ages; but until a week ago, mine was not far off. It had spent most of its long life stored in a box (long story), and last Friday might have been its first experience of a rainy ride.

As the rainy day went on, a matte area, soggy to the touch, gradually spread from the back towards the front. And today, four days later, it's still matte (though no longer soggy).

I'd assumed that the saddle was made of an impermeable plastic cover over some spongy substance. But whatever the cover is, it's not impermeable. Internally, I hope it won't get mildewy. Externally, how might I restore its semi-gloss? And is there some preventative treatment, or should I just cover it with a plastic grocery bag when out riding in the rain?

Chombi1 

Basically, water damage to the leather cover....
Unless you treat leather with something, it will absorb water and go matte on you.
The "scratched on" lines applied by the factory as decoration do not help as they give the water an easy way to get into the leather being that it is more porous than the smooth areas of the saddle.
I should eventually dry, but the matte look might stay for a while until you ride the saddle enough and naturally polish the surface with some wear, but areas that will not see wear might be matte for good.
You also should watch out for mold forming on the leather as it will discolor it to look all blotchy.. Try to seep out the moisture from the saddle as much as possible by maybe wrapping the saddle with paper towels until most of the moisture is taken out. The problem is, the foam padding between the plastic base and the leather cover is still retaining a lot of the water in the saddle and getting it all out will take a quite a bit of time.....
Using heat to dry (space heater?) could help, but it could also damage the leather if you are not careful.
We have leather saddle experts in this forum like RHM, I'm sure he will have some really good suggestions for a possible fix for you.

microcord

It's . . . leather? I'd taken it for granted that it was plastic. Well, that certainly explains things.

I have a single pair of black leather shoes that I wear for funerals, but otherwise my feet are always shod in various artificial substances. Treatment of any leather is merely a distant and hazy memory. Hmm, should I use dubbin, perhaps? (I remember my mother telling me that she stopped using it because it damaged the thread with which the shoes were held together, but thread doesn't seem to be an issue here.)

OTOH there's no gloss from dubbin, and there's wax as well as shine from regular shoe polish.

(I'm sure that whatever I apply, much of it will come off on my pants, to embarrassing/hilarious effect.)

Chombi1 

Turbos of that vintage were either smooth leather or patterned "buffalo" style leather, which I think yours is, or suede (sometimes called nubuck) or lycra with gel padding. There were few imitation leather saddles made by less known manufacturers, but they were mostly considered cheap stuff, as the imitation leather back then was not that good, did not breath and was prone to cracking. It was only in the later 90's that "Lorica" a breathable imitation leather product, became available to most saddle makers after the material was already well proven on other products like motorcycle racing and sport boots, and they started to use the stuff and it also became common in cars as the new "leatherette" seat upholstery.
A good amount of the reissued Turbo saddles these days have this leatherette material cover to satisfy the demand for "vegan" saddles that a lot of young riders prefer to ride these days.

microcord

Thank you for your patience with my ignorance, Chombi1. Yes, it's this patterned stuff. (Buffalo? Well well: I'd been wondering which critter's hide was being imitated.) Last week, my saddle looked identical to the one in the photo above, except that the fake brass (or real brass?) ornamentation wasn't/isn't quite so bright (and of course the lines were/are in slightly different places).

Whether or not because of age, the saddle isn't quite black: it has a just-discernible brownish tinge (which I find rather attractive).

Yes, polishing the saddle is perhaps a job for my butt.

due ruote 

Spaghetti Legs 

microcord

due ruote, Spaghetti Legs, thank you both very much.

I think the saddle is dry, so the next job is proofing (well, increasing resistance) and cosmetic restoration. I looked for "Obenauf" in the Japanese website of a certain large retailer, and found
tubs of "Obenauf's Heavy Duty Leather Protectant LP" for more than I've ever paid for a saddle. I'll be looking for an alternative brand. (Perhaps at a motorbike parts shop, for the maintenance of classic/retro motorbike saddles?)

Looking for "Obenauf" at the abovementioned retailer brought much else, including three books (or electronic quasi-books): The Virtue of Boredom; An Escort's Confessional; and Empaths and Sensitives: The Secrets to Attracting Beautiful Relationships While Maintaining Your Energetic Boundaries. I'll pass, at least until I've finished Bert Wagendorp's Ventoux.

Spaghetti Legs 

microcord

Now that's a very palatable price -- a pity that the page says "This item does not ship to Japan." Yes, I'll look around.

easyupbug 

If you are near an equestrian tack shop, should be one near anyone of the Japanese racing venues, they will help. I spend 20+ times more for my equestrian saddles than my bike saddles so care is very important.