Penetrants and emulsifiers should not...

• A. Be mixed between manufacturers
• B. Be mixed with compatible additives
• C. Be stored in the same container
• D. Be used with care

Answer: (A)

Penetrants and emulsifiers must stay within the same manufacturer's system because their formulations are designed to work together. Mixing products from different manufacturers can create incompatibilities that change how the penetrant wets the surface and how the emulsifier removes excess material, degrading flaw visibility or causing false indications. This is why cross-manufacturer mixing is avoided. Other statements describe general safe handling or potential allowances only when the supplier provides explicit compatibility guidance, but they don’t capture the specific incompatibility risk.