Most of the things I make are made with a high quality vegetable tanned leather. Vegetable tanned leather is very different from the leathers that are used in upholstery work like your home furniture or in your car and require a different approach for cleaning and maintaing.
Cleaning Vegetable Tanned Leather
There are many home made solutions and suggestions floating around the internet these days. But BE WARNED, many of the "home remedies" will do more damage to a vegetable tanned leather than good. These are often recommended for leather that is chrome tanned or one of several other processes and DOES NOT do well with vegetable tanned leather. For cleaning vegetable tanned leather use a good quality Glycerine Saddle Soap. Fiebing's makes a great product called, Fiebing's Liquid Glycerine Soap, for this and is used by leather crafters and proffesional leathersmiths worldwide. I prefer the liquid version to the bar type saddle soaps because it is easier to apply and much more user friendly and forgiving if a mistake is made. To use it simply spray it on to the area to be cleaned and wipe off any excess. Pretty Simple!
(As with any cleaning product be sure to read the label and follow any manufacturers instructions)
Conditioning Vegetable Tanned Leather
Once the piece of leather is cleaned and has had time to dry it will need to be conditioned. Conditioning replaces the natural oils found in the leather and gives it that soft supple feel that we all love. When looking for leather conditioners for vegetable tanned leather it's imperative that you read the labels on the products and stay away from ones that contain waxes. These work fine for protecting vegetable tanned leather, but will not absorb deep into the pores in your vegetable tanned piece. Try a product like Aussie Leather Conditioner or Pure Neatsfoot Oil. For either of these products use a soft lint free cloth applicator . Apply the product in a thin coat, it is MUCH better to use several light coats on this type of leather than one or two heavy coats, allow it to dry and wipe away any excess product. Repeated coats may be necessary to restore a really worn out piece. But be aware that the conditioner will darken the piece of leather slightly as it restores the natural oil's to the hide.
Protecting Vegetable Tanned Leather
Once the piece has been cleaned and conditioned it will be looking a lot better and will have that soft supple feel again. Now it's time to protect it and prolong the life of the leather. This is especially important if your piece of leather will see outdoor conditions such as a motorcycle seat, horse saddle and tack, etc... To protect it, look for a product that offers weather proofing or a water repellent, but it MUST be safe for use on vegetable tanned leather. Fiebings makes one called Snow Proof Paste that does a great job of sealing and protecting vegetable tanned leathers. It's not just for use in snow; if it will hold up and protect in the rigors of that harsh of an environment and quantity of water, then the abuse the leather gets from a little sweat or light rain is no big deal at all.