My son worked 6- years as a wildland firefighter. They swear by a product called "Obenauf's" he put this on his 400.00 fire boots every 2 weeks. They are walking in hot coals and wood ash. Wood ash and water forms acid that dries leather out in a heart beat. It comes in a paste and oil. I like the paste it is not as hard as Snow Seal you can work it into the leather with your hands no heat needed. It will darken the leather.