I have a recliner with some cat urine stains. Actually, they are cat spray stains that are a mixture of urine and scent gland excretions made by a male cat. The stains remained on the chair for many years before I decided to do something about it. The leather where the stains is is not degraded. It is as soft and supple as the unstained areas. I've cleaned the stained areas with vinegar and water and removed a lot of original stain. I could see the darkened urine coming off on the rag when I applied the vinegar solution. I would clean the area, wipe with a clean rag, and let it dry. I repeated this 4 to 5 times until, I now do not see any more dark urine on the rag after I apply the vinegar. I'd like to dye the chair a darker color. The chair is located in an area that gets afternoon sun and is quite faded. Also darker leather furniture is more fashionable, at least, in my part of the world. I've roughtly estimated the total area to be approximately 50 sq. ft. or 47 sq. meters