Adding conditioners to leather baseball gloves can increase their weight depending on the type of conditioner used and the amount applied. Heavy oils, waxes or petroleum jelly (vaseline) can weigh down the leather and make the glove feel heavier and more cumbersome. It can also make the leather feel greasy and increases the probability of the ball slipping out of the glove. However, using lighter weight conditioners or concentrates like Mitt-Spit Glove Oil adds very little weight. It only requires about 1/4 ounce of Mitt-Spit Glove Oil for an entire glove. Furthermore, much of the weight is the carrying agent of the active ingredient which rapidly evaporates away leaving a glove well moisturized without the sense of added weight. It's important to use the appropriate amount of conditioner to avoid over-saturating the leather, as this can also contribute to added weight and a less-than-optimal performance on the field. Overall, regular conditioning of a baseball glove is essential to maintain its suppleness and prolong its lifespan, but it's important to choose the right products and use them in moderation to avoid any negative effects on weight or performance.