Tech Tip: Proper Coolant Mixing Practices

Posted by Lube-Tech on Jun 26, 2018 9:45:24 AM

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When machining with water-soluble coolants, maintaining coolant stability is essential to produce quality parts and surface finish. Therefore, it is important to mix the coolant properly. 

Water-soluble coolants consist of both an oil phase (nonpolar) and a water phase (polar). These phases are extremely dissimilar, so they tend to separate from one another. Hence, emulsifiers are an important component in the coolant concentrate. Emulsifiers are molecules that consist of both polar and nonpolar sides, which help bring the two phases together.

Proper mixing techniques must be applied for the emulsifiers to orient themselves correctly between both phases and to ultimately maintain a homogenous mixture. If mixed incorrectly, the coolant emulsion will become unstable, and poor tooling and surface finish will result.

 mixing practices - emulsifiers

Coolant Mixing Tips

  • If possible, use a proportioner to mix and dispense fluid
  • Introduce the concentrate to water, not water to concentrate
  • Mix fluid thoroughly before checking concentration
  • Use water that is at least 50°F and not below
  • Daily make-up should be between 2-3% to maintain fluid concentration
  • If the concentration is high, DO NOT ADD ONLY WATER. This leans out in-use coolant over time and does not replenish important additives present in the coolant concentrate (biocides, rust preventatives, pH butters, etc.) Instead, provide a make-up of at least 1% concentrate
  • Do not introduce other coolants to the system


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