Silphium Extracts

This was originally a recipe by Rob Clarke,

It a common recipe, and can be found everywhere people talk cannabis online, or in his book, Marijuana Botany, which is essential reading in my line of work.

1. Silver Nitrate (AgNO3): Available from chemical suppliers.
2. Sodium Thiosulfate (Na2S2O3): Available from chemical suppliers or photography stores.
3. Distilled Water: To ensure purity in your solution.
4. Protective Gear: Gloves, goggles, and a mask for safety.
5. A Dark Glass Spray Bottle: To store and use the STS solution.
6. Measuring Equipment: Spoons, measuring cups, and scales for accurate measurements.
7. pH Meter or pH Strips (optional, but recommended): To check the pH of the solution.
8. A Dimly Lit Room or Work Area: Light degrades the STS solution.

Basic Safety Recommendations
The following steps require careful measuring, along with basic chemical safety. It is strongly recommended you work on a flat surface with a plastic sheet or several layers of newspaper to protect it. Silver nitrate does stain brown to black, so gloves and safety goggles are recommended.
Sodium thiosulfate has a very low toxicity, make sure you still wash up any spills well to remove all concern. Both of these solutions can be safely rinsed down the drain, when followed by a large amount of water.

Measuring and Mixing Stock Solution “A”

• Fill your 500ml measuring cup with 500ml of distilled water
• Measure out .5g of Silver Nitrate
• Mix the silver nitrate powder into the 500ml of distilled water
• Pour the silver nitrate solution into a brown glass bottle and seal tightly
• Label the bottle “A” Silver Nitrate
• Thoroughly clean the 500ml container and rinse with distilled water

Measuring and Mixing Stock Solution “B”

• Fill the 500ml container with 500ml of distilled water
• Measure out 2.5 grams of sodium thiosulfate anhydrous, OR 3.9g of sodium thiosulfate pentahydrate
• Mix the sodium thiosulfate with the 500ml of distilled water
• Pour the sodium thiosulfate solution into a brown glass bottle and seal it tightly
• Label the bottle “B” Sodium Thiosulfate
• Thoroughly clean the 500ml container and rinse with distilled water

Keep Both “A” and “B” Solutions Cool and Dark!

Mixing and Diluting STS
The next step is to mix the two stock solutions together properly, creating the actual Silver Thiosulfate Solution (STS).
Before using the STS, it must be diluted to a weak solution for spraying!

• Measure 50ml of stock solution “B” with the 60cc syringe and gently squirt it in the 500ml glass measure
• Thoroughly rinse the syringe with distilled water, or change to a new syringe
• Measure 50ml of stock solution “A” with the 60cc syringe
• While whisking solution “B” in the glass measure, slowly squirt solution “A” into the glass measure in less than 30 seconds
• Pour the mixed solution into the 32oz brown glass bottle with black sprayer top
• Add 900ml of distilled water to fill the sprayer the rest of the way, leaving room for a little bit of surfactant
• Add yucca extract in small amounts and shake well
• Test spray on a leaf to if solution still beads up and rolls off
• Add additional yucca extract and shake well, until the solution spreads across the leaf instead of beading up
• Thoroughly rinse all tools using more rinse water than usual

Final Notes:

Using STS to reverse the sex of cannabis plants is a powerful tool for breeders looking to produce feminized seeds. Proper handling and disposal of chemicals are crucial to minimize environmental impact and personal health risks.