BaCO3—alkaline earth—active high-temperature flux, but also promotes matt glaze surface. Unsafe for low-fire functional glazes. Source: Clay: A Studio Handbook Controversial in high-temperature functional glazes, but toxicity problems from balanced glaze not proven. Often used as additive in clay bodies in very small percentages to render sulfates insoluble, reducing scumming. Toxic in inhalation and ingestion. Source: Clay: A Studio Handbook

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