Various types of metal or synthetic substances are used for bit mouthpieces, which may determine how much a horse salivates or otherwise tolerates a bit; a horse having a moist mouth is considered more relaxed and responsive. Commonly used metals include stainless steel and nickel alloys, which generally do not rust and have a neutral effect on salivation; sweet iron, aurigan and copper, which generally tend to encourage salivation, and aluminum, which is considered drying and is discouraged as a mouthpiece metal.
Different materials, such as metals or synthetic substances, are used for bit mouthpieces, affecting how much a horse produces saliva or tolerates the bit; a horse with a moist mouth is seen as more relaxed and receptive. Frequently employed metals include stainless steel and nickel alloys, which generally do not corrode and have no effect on salivation; sweet iron, aurigan, and copper, which typically stimulate saliva production, and aluminum, which dries out the mouth and is avoided.