There are tests that are within our scope and tests that are not. However the tests we can do are more than good enough to ensure that our end product can be poured into the tank with confidence.
As you say the 10/90 only guarantees a @ 98% conversion and the test is 'invisible' as regards most monoglycerides. There is a simple remedy for this which is to do a very small further stage after you ger a clear pass. We are talking something like 0.25gms KOH/litre.
50/50 shake up is an excellent quick check for soap and also works to detect small amounts of glycerol. However the test is not quantitative, so will not tell you actual amounts of contaminants. You would be better to purchase a soap test kit which you can use in conjunction with your 50/50
Water- this really should be checked and as you say the clarity of the bio is no accurate indication. Best (cheapest) way to check is to build yourself a carbide manometer, you don't have to check every batch and once you have established a method that works well then don't deviate from it.
Waterwashing/settling There is no doubt that w/washing is superior but is more time consuming, if w/washed properly it will remove soap and free glycerine to levels of <10ppm.
Final filtration - as the bio at this point is easy to filter then select the finest filter you can use, there seems little point in doing anything else. If you really want good filtration at sub micron levels then use a centrifuge. I have found it still removes sub-micron particles of glycerol even after water washing.
I know I sounded sceptical with one of your recent posts re your drying method. I have tested many samples of bio from people and the water content is usually high if dried by spraybay or similar methods. Also I have found that using filters that claim to absorb water also don't work.
I purchased a 'hippo' polishing pot some years ago. The filter is 3 micron absolute. The claim is also that the filter can absorb water (from memory it can absorb 750gms of water) I did some before and after tests on mine and found it absorbed no water at all.
Hope this helps you Bio Boy, Dave.
