The Hot Pan Test

By Rick Da Tech


The HPT or "Hot Pan Test" is a quick, unscientific and non-quantitative test to check for the presence of water in vegetable oil [VO]. The HPT is similar to the Crackle Test, but uses a larger sample. These videos illustrate the HPT procedure.

The HPT is not "foolproof" by any means. False positives can be obtained if the pan is WAY too hot or if solvents are mixed in the VO. False negative results are possible if the sample contains suspended water that has high concentrations of salt/sugar/acids.

Dana's Hot Pan Test

Dana uses his test to test WVO to see if it's dry enough to use without converting to biodiesel in vehicles modified to burn WVO.

Do not pour in a sample with any visible water. If water droplets are visible no testing is needed. There is water present in your sample. Visible droplets of water will spatter hot oil out of the pan and may cause burns or fire.

  1. Smear a finger of wvo across a fry pan (cast iron preferred)as a temp check.
  2. Keep the sample of wvo to be tested handy. Enough for 1/4"-3/8" thickness covering the bottom works best.
  3. Heat the pan on high temp until the smear begins to produce smoke then pour in the sample.
  4. Look closely at the bottom of the pan where the oil meets it. Are there very small bubbles forming? This indicates some suspended water.
  5. The number of bubbles indicates how much water is present in suspended form. I usually accept a FEW suspended bubbles (up to 3 per sq inch maximum). Lots of small bubbles is unacceptable to me.
  6. If crackling or popping is heard..way too much water is present for the VO to be safely used as fuel.


  • Do not average bubble count. The visibility of bubbles is dependent on the temp of the underlying pan and this may be regionalized depending on your heat source.
  • If the pan has been washed or not used previously it must be "seasoned" to make certain that no moisture is trapped in the pores on the surface of cast iron.
  • False positive results (bubbles) can be obtained if the pan is WAY too hot..or if solvents are mixed in the WVO.
  • False negative results (no bubbles) are possible if the suspended water has high concentrations of salt/sugar/ acids.


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