The 5 Tests Every Home Brewer Should Know
By Rick Da Tech
1) Testing finished biodiesel for water.
Water in our biodiesel will make it cloudy or turbid. If the biodiesel is clear enough to read a newspaper through a sample then conventional wisdom is that it's dry enough to use in a vehicle.
The test is temperature dependent since hot biodiesel can hold more water without going cloudy than cold biodiesel. To make sure you have your biodiesel dry enough to use, put it in the refrigerator and chill it down below the coldest temperature your batch of biodiesel is likely to see. If it's going to be used right away then look to the nightly lows. If it's going to be stored long term, then look to the historical lows for the period you expect to store it. If the biodiesel gels up before going turbid then you have dry biodiesel.
The problem with this test, is that ASTM requires less than 500 ppm of water in biodiesel that is to be blended with diesel and biodiesel will hold 1500 ppm of water before going cloudy. So we can pass this test and fail for ASTM water levels. To Make sure your fuel meets the ASTM standards, use the Carbide Manometer or Sandy Brae test.