When purchasing Lamp Black, you must prioritize particle size distribution and surface area (BET), as these determine the pigment's tinting strength and dispersibility. For high-end coatings or inks, look for a low grit content (sieve residue <0.02%) to prevent surface imperfections. Additionally, verify the pH value; a neutral or slightly alkaline pH is often preferred for compatibility with various resin systems. Ensure the oil absorption value aligns with your formulation needs to manage viscosity effectively.