Originally Posted by observant_imp
Anonaperson--what type out output and longevity do you get with your recipe?
Let me pull some of the records from when I was obsessing about THAT....
First, I used Knox gelatine powder since is is cheaper than Jello and has no artificial flavor or color.
Ok, my first test was 4 pkt gelatine, 2 cups water, 2 cup sugar for gelatine, chilled solid in round 2 liter juice jug. Then 1/2 cup water, 1/2 teaspoon yeast, 1/4 teaspoon sugar to get the yeast started. Then I think I filled the jug up with water, no notes here, I doubt I had only 1/2 cup of water in the jug! Didn't count bubbles, until day 10, it was so fast (guessing 50+ bpm), day 10 was 25 bpm, day 25 was 12 bpm, day 33 was 10 bpm, then I stirred the solid jell with a stick on day 38 and added tap water to get 16 bpm, fixed a leak on day 39 to get back to 10 bpm. Poured off some water and replaced on day 46 to try to get above 7 bpm, stopped on day 50 at an unstable 5 bpm. I think there was still gelatine left in the jug.
Then I started experimenting. Next was 2 1/2 cups gelatine, made with 2 cups water total, 2 pkts of gelatine, 1 cup sugar (note half the sugar as before), chilled in the bottom of jug. 5 1/2 cups liquid, 1/4 teaspoon bread yeast. Took one day to start, temp 64 that day, later days room temp was warmer. Got to 12 bpm on 3rd day, stayed at 8 to 12 bpm until day 21, then tapered to 5 bpm on day 30. I did open it and add 2 teaspoons baking soda on day 38 and a bit of salt after day 40. (note, the salt is a bad idea I later discovered)
I experimented with using "yeast nutrient" from the brew store, it tended to make it foam, particularly with gelatine, but it was a good thing to add to sugar water mixes.
I learned that starting with hot water was a bad mistake, I would think it had cooled but I guess it still had hot spots to harm the yeast. I learned that baking soda was a necessary addition, even though my tap water is KH 9 and lots of calcium, low magnesium. I learned that wine and beer yeast did not like baking soda but bread yeast did. I suspect acid/base requirements of the different yeasts. I found that the water in the jug gets very acidic, and if you add baking soda later it will explode -- eew! stinky sticky mess!
Cutting the gelatine into cubes gives a lot more surface are for the yeast to act upon, and so will shorten the life of the mix while boosting the rate.
My records end after a dozen tests, after that I just kept a tag on the bottle to tell me what a jug had in it and when it was replaced, so those records are lost now. I was looking for a more steady rate and not that concerned with lifespan and so I ended up reducing the sugar and cubing the mix to get a pretty stable rate that lasted 3 weeks roughly. I was using 2 cups of sugar in 4 packets of gelatine, 3 cups of water in the gelatine total. Of this pan of gealtine, I'd use 1/4, and keep the rest in the fridge -- beware, for sometimes it will mold before you get that last 1/4 used. In the bottle I'd put 1 teaspoon baking soda, 1/4 teaspoon yeast and water to 3" from the top, at that point. Near the end, I started using 1/3 of the pan of gelatine, and I think the molding of the last bit actually happened more often, so it may have been lasting much longer, sorry no notes!!
The sugar to gelatine to water mix is important. The first test was 2 cups of sugar in 4 pkts of Knox and was too strong. At the end I was using 1/2 cups of sugar and 1 pkt of Knox per bottle, which was 1/4 of the pan of Knox blocks.