Okay, now that you have read about, and hopefully did, the basic transesterification process
We will get a little more in-depth about the reaction.

This process. the base/base method, was developed by the folks at the University of Iowa.
They conducted an in depth analysis of the process with the goal of getting the most complete reaction with the minimum amount of methanol and catalyst. This is the result.

There are currently two accepted methods. We will look the one most home brewers are using first.

80/20 - 80/20

As you might have guessed, the numbers represent the first stage and the second stage reactions.

The number 80/20 - 80/20 represents the amount of methanol and catalyst to use for the first reaction.

The second set of numbers 80/20 -80/20 represents the amount of methanol and catalyst to use in the second reaction.

Now there is a common misconception out there that the base/base method uses more methanol and catalyst. Not true, it is the same amount as you would use for a single reaction, just split into two parts. Actually, most people find they can use LESS of these using this method. More on that a little later.

So you might be thinking "Why does this work better?". Here is why.

In the first reaction, the methanol and lye are "used up" very quickly creating a large amount of glycerol. This glycerol will attract and absorb a portion of your methanol and catalyst. What is absorbed is not available to complete the reaction. Therefore, it goes to waste and gets drained out with the glycerol.

Bring in the 2 stage reaction! The portion in the second stage is held out and therefore not wasted. The first reaction will remove a LARGE amount of the glycerol. What is left is biodiesel and un reacted oil, but in a much purer state. Now that the majority of the FFA's and impurities are removed, the second stage can come in and finished the job!

Now you add the second stage and mix longer. How long you mix it will vary. We have more information on this under the testing section.

After this final stage, just as the first, you will glycerol settle-out. Just significantly less. It will also be a whole lot lighter in color than the first reaction and you will notice your biodiesel will also be lighter in color (less glycerin!)

So, as you can see, the base/base reaction process make much better use of your raw materials and in the end will save you money and give you a MUCH better product.

Lets face it, we do the reaction to remove glycerin. the single stage reaction just does not do the job well. It leaves a considerable amount behind, which is not good!

I stated above there are two base base methods. The methods actually pioneered by the University of Iowa was basically the same, accept that they used 90/10 - 90/10. We have tried it and it does work. We have found for high FFA oil, like WVO the 80/20-80/20 seems to work better and is more repeatable.

I recommend you try both and use what works best in your situation.