Asked by ssbothwell ·July 14, 2020 ·18.7k readers

Various FPJ Questions

Hi. I recently discovered KNF and it really resonated with me. I've been going through as much reading material as possible and last week I made a batch of Comfrey FPJ following the instructions in Chris Trump's How To FPJ video. After making my FPJ, I read in this paper that you need to stabilize your FPJ by adding equal parts by weight of brown sugar to the solution. I did this yesterday and then later saw people on this board suggest equal parts by volume, which is a very different quantity of sugar. Today I checked on my FPJ and it looks like most of the sugar went out of solution with the FPJ:

OK, finally here are my questions:

Did I add way too much sugar?
If I siphon off the FPJ from the mass of sugar below will it be super saturated properly now?
If I make another batch of Comfrey FPJ, would it be ok to reuse the excess sugar from this batch?
After super saturating FPJ, should I adjust the application ratio to account for the additional sugar diluting the FPJ?
Without super saturating, roughly how long is FPJ good for at room temperature and in the refrigerator?
When making FPJ, Drake says to only use a sugar cap when fermenting fruit. However, Chris Trump adds one in his video when using Banana Flowers and says the cap is very important. When should and shouldn't I use a sugar cap?

Thank you for everyone for helping spread the knowledge of KNF!

fpj storage super-saturation

The answer

hugoflmatos · Jul 17, 2020 ✓ Marked as the answer

Hi there,

Yes, so here is the deal: when adding sugar you should stir the solution, at first you'll notice how fast the sugar sinks and dissolves, when aproaching saturation the sugar will sink in "slow motion" and need more stirring to dissolve, but when you see sugar precipitating at the bottom and not dissolving, regardless of how much you stirr, then the FPJ is saturated.
Most likely yes, if not i guess it will be very close to, but just add a little bit of sugar until you notice it precipitating at the bottom, then you know for sure its super saturated.
You could try, in theory the microbes there wont differ but keep in mind that the sugar is no longer dry, so im not sure if it will create enough (if any) osmotic pressure to extract everything from the new plant material. Anyway, you still could use that sugar in the kitchen for example.
Not sure i understood what you mean here.
Outside I would say 3-7 days, depending on your specific conditions, temperature mainly. Just check that yourself, if you see bubbles in the FPJ, they are still there, when bubbles become less intense its an indicator the food is running out and the microbe population is fading. When the solution starts smelling like alcoohol then it's already degrading, it is still usable but less effective. In the fridge at least 6 months.
If you think of it, banana flower is a material with more in common with fruit than with the tender parts of plants we use in FPJ, I believe that's why Chris does the sugar cap. So I would say sugar cap for fruit or fruit like plant materials, stuff which is denser and has more fiber in it when compared to regular tender shoots or leaves (which is what we use in FPJ).

Hope it helps!

From the KNF library

From the KNF library Drafted by Claude from Office Hours and the books · Sep 2026 · 3 sources

The sources disagree on how much sugar. The UH manual adds an equal amount of brown sugar by weight for long-term storage. The Pure KNF Manual says the sugar content of poured-off solution varies, so add equal volume to be safe. (Pure KNF Manual, p. 80) To save sugar, it says add the sugar slowly and stir thoroughly. (Pure KNF Manual, p. 80)

Dilution: FPJ is mixed with water at 1:500. (Student's Manual, Basic Course, p. 37) Go more dilute, 1:800 or 1:1000, when the FPJ is over a year old and highly concentrated. (Student's Manual, Basic Course, p. 37)

Storage: Cho says use FPJ within two or three days of full fermentation, when it works best. (Cho, Theory, p. 71) To keep it longer, he adds more sugar so it does not oxidize or turn to alcohol. (Cho, Theory, p. 71) Store it in a dry, cool place out of direct sunlight. (Student's Manual, Basic Course, p. 37)

Sugar cap: Cho covers the top of the filled container with sugar. (Cho, Theory, p. 71)

The library gives no shelf life at room temperature or in the refrigerator. It says nothing on siphoning, reusing sugar, adjusting the ratio for added sugar, banana flowers, or Drake's fruit-only cap rule.

Sources

p. 37 Student's Manual, Basic Course · “FPJ is mixed with water at a ratio of 1:500.”
p. 80 Pure KNF Manual · “Supersaturating PureFood is a different story as the sugar content of the poured off solution will vary.”
p. 71 Cho, Theory · “two or three days after the full fermentation since the time is the most effective period for crops.”