We know it’s important to properly apply oil or conditioners to leather.  What’s also important to know which oils are good for leather and which can go rancid. Have you ever heard of the iodine index? This measurement is used to determine the potential for rancidity in oils, which is an important factor to consider for health reasons.

The iodine index, sometimes called the iodine value, is a measure of the unsaturated fatty acids present in an oil which determines the oil’s potential for rancidity. Unsaturated fatty acids contain double bonds between carbon atoms, which can become rancid when exposed to oxygen and heat. The iodine index is determined by adding iodine to the oil, which reacts with the double bonds to form a complex that can be measured.

The higher the iodine index, the more unsaturated fatty acids are present in the oil. This means that the oil is more susceptible to oxidation, which leads to rancidity. Rancidity is characterized by a stale, unpleasant, unhealthy odor.  I’m sure you’ve seen young boys and girls standing in the outfield totally bored and literally putting their mitt in their mouth.

Different oils have different iodine indexes, depending on their composition. For example, coconut oil has a very low iodine index of around 10, which means it contains mostly saturated fatty acids and is less prone to rancidity. On the other hand, soybean oil has an iodine index of around 130, indicating that it is high in unsaturated fatty acids and more prone to rancidity. 

It's important to note that not all unsaturated fatty acids (oils) are created equal. Neat’s-foot oil has a value of about 72.  Mink oil runs about 88.  Mitt-Spit Glove Oil has an iodine index of about 1.  Making Mitt-Spit Glove Oil by far the safest to use to prevent rancidity.

The iodine index is an important measurement for assessing the potential for rancidity in oils. Oils high in unsaturated fatty acids are more susceptible to oxidation, which leads to rancidity. By choosing oils with lower iodine indexes, we can reduce the risk of rancidity and enjoy healthier lifestyle.