Hi all,
according to this meaningful 2018 study ...
Interest in hemp (Cannabis sativa) for its medicinal compounds, cannabidiol (CBD), and Δ-9-tetrahydrocannabidiol (THC), continues to increase. Maximizing yield of CBD and/or THC requires female plants because female inflorescences accumulate significantly greater concentrations of these...
journals.ashs.org
and this source ...
..as well as the study they are based on from the early 80s, the STS should be prepared with a molar ratio of 1:4.
If my calculations are correct, that would mean a weight ratio of 5.835:1 for the two components using the Pentahydrate version.
Many older tutorials seem to have taken the second source with its 20/80 solution mix and just quadrupled the amount of Silver Nitrate to get the same amount of A/B solutions, but this lowers the total dosage by a factor of 2.5 because the additional water also dilutes the other component accordingly! However, the very high amount of 20 mM would then still come out as 8 mM, or 0.8 mM after 1:9 dilution. Good enough, but not perfect, as the first source above suggests.
For the ~3 mM solution from the study with nearly 100% success, that would be 0.1g Silver Nitrate and 0.58g Sodium Thiosulfate mixed with 100 ml of distilled water each (=2.92 mM), NOT diluted any further.
Application is done 3 times: once directly before switching 12/12, once a week later, once another week later.
I have found this to work perfectly as long as temperatures are not too low. I did have problems with plants in a basement at 14°C. No problems at 20°+ and complete conversion.
The amount of pollen starts very small but gets larger later. What helps a lot is drying the sacks or, later, the entire plant, because otherwise moisture from the plant tissue soaks up the little pollen there is. For this, flowering has to be induced a few weeks earlier than for the one that is to be pollinated, but just a week earlier works as well.