Professional STS Guide: How to Reverse Cannabis for Feminized Seeds.
The Master Breeder's Guide to STS Reversal
We developed this guide specifically for Ontario growers working with hardy Canadian genetics.
By Twisted Genetics: Professional Feminized Seed Production
At Twisted Genetics, we don't just "spray silver." To ensure 99.9% feminization stability for our Purple Kush Auto and future genetics, we use a lab-grade Silver Thiosulfate (STS) solution. This professional method is more reliable and less stressful for the plant than standard colloidal silver.
Pro Tip: Never use tap water for STS. The chlorine and minerals will cause the silver to "bond" and fail. Distilled water only ensures the chemical stays active for the plant.
Why STS Beats Colloidal Silver
Systemic Action: STS is absorbed better by the plant, meaning fewer sprays are needed.
Higher Pollen Yield: It produces more viable, fertile pollen than other methods.
Stability: STS blocks ethylene (the hormone that makes a plant female) more effectively, ensuring your seeds are truly feminized.
The Twisted Genetics STS Recipe
To make a stable Stock Solution, you must keep your chemicals separate until the moment you mix.
Part A: Silver Nitrate Solution
Mix: 0.5g Silver Nitrate into 500ml Distilled Water.
Storage: Amber glass bottle, wrapped in foil, stored in a dark fridge.
Part B: Sodium Thiosulfate Pentahydrate Solution
Mix: 2.5g Sodium Thiosulfate Pentahydrate into 500ml Distilled Water.
Storage: Cool, dark place.
The "Golden Rule" Mixing Step
When you are ready to create your Stock STS, you must always pour Part A slowly into Part B while stirring.
Warning: If you pour B into A, the silver will "crash out" (precipitate), turning the liquid cloudy and useless. A proper mix stays crystal clear.
The Application Schedule (Autoflower Edition)
Since Autoflowers have their own internal clock, timing is everything.
The First Sign: Apply your first spray as soon as the first "pre-flowers" (pistils) appear.
Dilution (The Working Spray): Mix 1 part mixed STS Stock with 9 parts Distilled Water.
Application: Spray your target branch until dripping.
Repeat: Spray every 5 days for a total of 3–4 applications.
Safety: Always spray right after the lights go out. This prevents "light burn" on the leaves and keeps the STS from breaking down.
Post-Treatment Care
PPM Management: STS is a salt. Keep an eye on your runoff using the VIVOSUN guide. If your plant looks stressed, check that your PPM is between 600-800 for established veg.
Zero Waste: Never consume or smoke a plant that has been treated with STS. These plants are for Pollen and Seed production only.
Troubleshooting STS and Facts
Why did STS fail?
most common would be.
"Using tap water instead of distilled" (the minerals ruin the silver), "Mixing in the wrong order" (pouring B into A), or "Applying under heavy lights" (UV light kills STS).
Pro Tip: Never use tap water for STS. The chlorine and minerals will cause the silver to "bond" and fail. Distilled water only ensures the chemical stays active for the plant.
We perfected this reversal timing specifically for the Ontario photoperiod and Canadian autoflower cycles.
Treated plants are never for consumption. Dispose of treated foliage responsibly.
The Ontario Advantage
Bred in the heart of Ontario, we use this STS method to ensure our Purple Kush Auto can handle the unique humidity and light cycles of the Great Lakes region.
frequently Asked Questions Mastering STS Cannabis Reversal
How long does mixed STS solution last?
Once you combine your Part A (Silver Nitrate) and Part B (Sodium Thiosulfate) into a Stock Solution, it is viable for 30 days if stored in an airtight, light-proof amber glass bottle in a cool refrigerator. The individual, unmixed powders have a near-indefinite shelf life if kept dry. If you see black or grey "precipitate" (bits) in your liquid, the silver has fallen out of solution and it is time to mix a fresh batch.
Can I save and store feminized pollen?
Yes. To store pollen long-term, it must be kept bone-dry. We recommend mixing your collected pollen with toasted flour (ratio of 4:1 flour to pollen) to act as a desiccant. Place it in a sealed, airtight vial with a silica gel packet and store it in the freezer. When frozen correctly, feminized pollen can remain viable for up to one year.
What are the signs that the STS reversal is working?
Typically, between 14 and 21 days after your first spray, you will notice the plant's growth "stalling" or lagging—this is a sign the chemical is working. Soon after, you will see the formation of male pollen sacs instead of white pistils. For stubborn strains, you may need a fourth application to ensure full conversion.
Can I use tap water for my STS mix?
Never. The minerals, chlorine, and fluoride in tap water will immediately react with the Silver Nitrate, causing it to "crash out" and turn cloudy. This neutralizes the solution, making it useless for reversal. Always use 100% Distilled Water for both the stock solutions and the final spray dilution.
Can I smoke the plant after I’m done?
No. Any part of a plant treated with STS contains heavy metal residues. This material is strictly for breeding purposes only. At Twisted Genetics, we prioritize safety: treated plants should be harvested for seeds/pollen and then safely discarded. Do not consume, vape, or make edibles with treated material.
Need Expert Help or Lab Supplies?
At Twisted Genetics, we are more than just a seed bank—we are active breeders. If you are a Canadian grower looking to start your own reversal project and need high-purity Silver Nitrate or Sodium Thiosulfate Pentahydrate, we can help you source the professional-grade chemicals you need.
If you have questions about the timing for a specific strain or need troubleshooting on a reversal that isn't dropping pollen, feel free to reach out to the Twisted Genetics team. We are here to support the Ontario growing community of all growers with real, breeder-level expertise.
Contact Us Today for Lab Supplies or Breeding Support
Why did STS fail?
most common would be.
"Using tap water instead of distilled" (the minerals ruin the silver), "Mixing in the wrong order" (pouring B into A), or "Applying under heavy lights" (UV light kills STS).
Pro Tip: Never use tap water for STS. The chlorine and minerals will cause the silver to "bond" and fail. Distilled water only ensures the chemical stays active for the plant.
We perfected this reversal timing specifically for the Ontario photoperiod and Canadian autoflower cycles.
Treated plants are never for consumption. Dispose of treated foliage responsibly.
Mandatory Safety & PPE: Why We Don't Take Risks
Handling the chemicals for STS reversal requires professional respect. At Twisted Genetics, we prioritize garden safety and human health. You must use the following Personal Protective Equipment (PPE) whenever mixing or spraying:
1. Chemical-Resistant Nitrile Gloves
Why: Silver Nitrate is a caustic salt. If it touches your skin, it reacts with your proteins to create Silver Chloride, leaving stubborn black or brown stains that can last for weeks. High concentrations can cause actual chemical burns or tissue damage.
2. Protective Eyewear (Safety Goggles)
Why: This is the most critical rule. Accidental splashes of Silver Nitrate in the eyes can cause severe irritation, corneal damage, or in extreme cases, permanent vision impairment. Never mix these chemicals without sealed eye protection.
3. Dust Mask or Respirator (N95 Recommended)
Why: When handling the dry Sodium Thiosulfate or Silver Nitrate powders, you must avoid inhaling the dust. Inhalation can irritate the respiratory tract, causing coughing or shortness of breath. Long-term exposure to silver dust can lead to Argyria, a permanent blue-gray discoloration of the skin and internal tissues.
4. Long Sleeves and Proper Footwear
Why: To prevent "permeation" (where chemicals soak into your clothes and sit against your skin), always wear long sleeves and closed-toe shoes. If you spill the solution on your clothes, change them immediately.
Environmental Responsibility & Disposal
Never Smoke Treated Plants: This is non-negotiable. Plants treated with STS contain heavy metal residues (silver). Smoking or consuming these plants can lead to heavy metal poisoning.
Safe Disposal: Silver Thiosulfate is highly toxic to aquatic life and can damage soil microbes if dumped down the drain or into the garden. Once your seeds are harvested, dispose of the treated plant material in the trash, not your compost pile.
Storage: Keep your Stock Solutions in labeled, child-proof glass containers in a cool, dark place (like a dedicated seed fridge) away from food and drink.
Genetics Bred for the North: The Ontario Advantage
The Twisted Genetics STS protocol wasn't just copied from a textbook—it was refined right here in Ontario. We developed our specific timing and 1:9 dilution ratios to work with hardy, short-season genetics like our Purple Kush Auto.
Growing in the Great Lakes region means dealing with unique humidity spikes and unpredictable light cycles. By using this lab-grade reversal process, we ensure our seeds carry the stability and vigor required to thrive in the Ontario climate, whether you are growing in a high-tech indoor tent or a Southern Ontario backyard.
