Welcome to the Lounge, SET.
1) I've heard rumors that Gary White the custom hatter is the only hatter that stocks the onionskin. I'm not sure, though.
His website: www.custom-hatter.com
I agree with Dinerman that the onionskin often creates more issues than it solves.
2) In my experience, the simplest solution is to carry large white cotton hankies with you. Wipe the sweat off the front section of the leather sweat and off your forehead, and do it as frequently as the heat demands. What's most destructive to the leather is of course the dried salts contained in the sweat; if you wipe off the sweat while it's still watery you will also remove most of the salt along with it.
When you return home from the heat, wipe the leather band with a damp cloth to remove the superficial salt stains that may have accumulated during the day. Apply a small amount of water-based leather conditioner to give back the oils. I use a water-based cream with almond oils that smells good and is quickly absorbed by the leather. Terpertine oil based or petroleum based leather conditioners wouldn't smell good and wouldn't be absorbed as quickly. Else you can use whatever is within reach - sometimes I only had sunscreen handy.
It's a bit like shoe care - you don't have to do it every day, just regularly.
That is what I do.+1 on Rabbit's advice here. In my youth I watched local farmers wipe the sweatbands of their hats and wipe their foreheads frequently.
this one sounds like a better idea, i just tried shea butter, it seemed to do well and not retain unwanted waxes for any long period of time, the picards, was petroleum based i wrote them ----- i don't like petroleum based anything, natural waxes seem to be the best-------I like Lord Sheraton Leather Balsam (beeswax based) not sure whether its available outside the UK though.
Honest questionLeather sweatbands are thin and have a life. When they dry and become brittle, their life is at an end. Moisturizing the leather will not bring it back. It might soften, but it will have the strength of a wet tissue. If retaining the original sweatband in a hat is important to you, pay close attention to the condition of the sweatband before you purchase a hat. Don't sweat a sweatband that has seen the end of its life. It can be replaced and the hat will wear as good as new.
For a sweatband in good supple condition, the oily moisture from your forehead will be a good conditioner. Other treatment is not necessary or helpful.
Honest question
Doesn't that oily moisture from your forehead contain a lot of salt that will remain when the perspiration is gone and eventually dry out the leather ?
I was always under the impression that the salt in our perspiration was the ultimate enemy of soft leather in the long run
Beer
I don't know exactly what you're replying to, but I wholly endorse this post.
Honest question
Doesn't that oily moisture from your forehead contain a lot of salt that will remain when the perspiration is gone and eventually dry out the leather ?
I was always under the impression that the salt in our perspiration was the ultimate enemy of soft leather in the long run
Wouldn't it be great to know the treatment that was applied to Stetson's Fray sweatband?!