As an expert in leather tanning would tell you the process for baseball glove leather is quite involved. Tanning is a crucial step in transforming raw animal hides into durable and flexible leather. It involves treating the hide with certain chemicals to stabilize the proteins and prevent them from decomposing (stops the rotting process), thus creating a material that is suitable for baseball gloves.

Here's a simplified explanation of the tanning process:

Preparation: The first step is to prepare the raw hide for tanning. This involves removing any flesh, hair, and fat from the hide, usually through a process called fleshing.
Soaking: The hide is then soaked in large vats of water to rehydrate the collagen fibers and make them easier to work with. This process can take several hours or even days, depending on the thickness and quality of the hide.
Liming: After soaking, the hide is treated with an alkaline solution, typically lime, to remove any remaining hair and other non-collagenous materials. This step also helps to open up the collagen fibers and prepare them for the tanning agents.
Dehairing: In some cases, additional dehairing may be required to ensure all the hair is removed. This can be done mechanically or through the use of enzymes or chemicals.
Pickling: The hide is then placed in a solution containing salts and acids to lower its pH and prepare it for the tanning process. This acidic environment helps to prevent the hide from putrefying and prepares it for the penetration of tanning agents.
Tanning: The actual tanning process begins by treating the pickled hide with tanning agents. There are various types of tanning agents available, including vegetable tannins, chrome salts, and synthetic tanning agents. Each type has its own characteristics and results in different leather properties. For baseball glove leather, chrome tanning is commonly used due to its ability to produce soft and pliable leather.
Post-Tanning: After tanning, the leather undergoes a series of processes to further improve its quality. These can include washing, neutralization, dyeing, and fatliquoring. The leather is stretched and dried to the desired moisture content, which allows it to retain its shape and prevent shrinkage.
Finishing: The final step in the tanning process is finishing, where the leather is treated with various substances to enhance its appearance, texture, and durability. This can include applying pigments, dyes, oils, and protective coatings.

Now, let's discuss why leather is tanned. Tanning is essential for several reasons:

Preservation: Raw hides are perishable and will decompose if not properly treated. Tanning stabilizes the proteins in the hide, making it resistant to decay and preventing the growth of bacteria and fungi.
Strength and Durability: Tanning transforms the hide into a strong, flexible, and durable material. It improves the tensile strength and tear resistance of the leather, making it suitable for demanding applications like baseball gloves.
Softness and Flexibility: The tanning process allows the leather to retain its natural properties while also making it soft and pliable. This ensures that baseball gloves are comfortable to wear and provide a good grip. Though when new, baseball glove leather can be quite stiff and require “breaking in” the leather with products like Mitt-Spit Break-in. This is best done with application of break in products to the leather that will accelerate its softening without damaging the leather fibers.
Water Resistance: Tanning agents, especially chrome salts, impart water-resistant properties to the leather. This is beneficial for baseball gloves, as it helps them maintain their shape and performance even in wet conditions.

Leather is porous so it looses the moisture imparted through the tanning process. This is why applying Mitt-Spit Glove Oil to the leather is important as it replenishes the proper oils. Be sure to usa an oil (Mitt-Spit Glove Oil is perfect) with a low iodine index else you run the risk of the oil turning rancid.

Bottom line, the tanning process for baseball glove leather involves several steps, including preparation, soaking, liming, dehairing, pickling, tanning, post-tanning treatments, and finishing. Tanning is also necessary to preserve the hide, improve its strength and durability, enhance its softness and flexibility, and provide water resistance.