How to Hot Pan Test

Collecting, filtering and dewatering of WVO SVO vegetable oil. For Biodiesel producers too.

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How to Hot Pan Test

Postby SunWizard » Thu Oct 07, 2010 2:10 pm

The "Hot Pan Test" (HPT) is a quick, unscientific and non-quantitative test to check for the presence of water in SVO. Its a small variation on a very old test called the "crackle test", by using a little more oil than they used to.

It works, although it 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 SVO. False negative results are possible if the sample contains suspended water that has high concentrations of salt/sugar/acids.


Smear a finger of SVO across a frying pan (cast iron preferred) as a temp check.

Keep the sample of SVO to be tested handy. Enough for 1/4" thickness covering the bottom works best. Heat the pan on high temp until the smear begins to smoke then pour in the sample. If you have an infra-red thermometer, this should be at the temp of 350-400F.

NOTE: 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 a fire. If you hear crackling, this is way too much water.

Make sure you have bright lighting on the pan. Look closely at the bottom of the pan where the oil meets it. Are there very small bubbles forming? This indicates water is present in the SVO. The number of bubbles is a rough indicator of how much water is present. Look quickly since the bubbles will evaporate to steam within a few seconds. I always dewater until there are no bubbles.

Now that I have been testing and comparing many other water testing methods, I have found that even no bubbles can mean a large amount (1500 PPM) of water is present if the SVO is old and abused (high FFA.) I am going to quit using the HPT and mainly use my Homebrew capacitive water in oil % saturated meter link
which is much easier and more accurate than a HPT.
YVORMV - Your veg. oil results may vary.
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