Silver Thiosulphate Mixing Guide, Overnight vs Pulse Dosing & Safety Precautions
S.T.S. is the worldwide industry-standard anti-ethylene treatment for carnations, snapdragons, delphiniums, gypsophila, larkspur, lisianthus, stocks, and lilies. While the treatment is most potent when applied by growers immediately post-harvest, wholesale florists also benefit when conditioning untreated sensitive stock.
Solution Strength: 2.0 mM S.T.S.
Environment: Room temperature (approx. 20°C).
Procedure: Stand stems in 2.0 mM S.T.S. solution in clean plastic buckets for 15 minutes. A 10-stem bunch should absorb 2.5 to 25 mL of solution during this period. Transfer stems immediately to fresh water or preservative for at least 1 hour to allow silver ions to travel up into the flower head.
Solution Strength: 0.2 mM S.T.S. (10x more dilute).
Environment: Cold room (0°C – 2°C).
Procedure: Stand bunches in 0.2 mM S.T.S. solution inside the coolroom overnight. Target uptake is between 25 and 250 mL per 10-stem bunch. Lower concentration prevents leaf margins from burning during extended immersion.
Never mix dry chemical salts directly into each other. Always prepare two separate liquid stock concentrates first using clean dark plastic or amber glass containers stored away from light.
Dissolve 17 grams of Silver Nitrate in 1 Litre of distilled or demineralized water.
⚠️ Warning: High quality distilled or deionised water is essential. Tap water chlorine will react, turning the solution black and cloudy. Silver nitrate crystallizes into toxic salts and causes brown skin stains that take weeks to wear off. Always wear protective gloves.Dissolve 100 grams of Sodium Thiosulphate Pentahydrate into 4 Litres of clean water.
Never reverse this order or pour the two concentrates together without water, otherwise silver thiosulphate will precipitate out and become useless.
For every 1.0 mM of required silver concentration in 10 Litres of treatment solution, you need 100 mL of Silver Nitrate stock and 400 mL of Sodium Thiosulphate stock. The table below outlines standard 10L bucket recipes:
| Desired Strength | Application Type | Water Volume | Sodium Thiosulphate Stock | Silver Nitrate Stock |
|---|---|---|---|---|
| 0.2 mM | Overnight / Coldroom (24 hrs) | 9,900 mL (9.9 L) | 80 mL | 20 mL |
| 0.5 mM | Extended Cool Soak (6–8 hrs) | 9,750 mL (9.75 L) | 200 mL | 50 mL |
| 1.0 mM | Medium Pulse (1–2 hrs) | 9,500 mL (9.5 L) | 400 mL | 100 mL |
| 2.0 mM | Standard Fast Pulse (15 mins) | 9,000 mL (9.0 L) | 800 mL | 200 mL |
| 4.0 mM | Ultra-Short Dip (Specific Crops) | 8,000 mL (8.0 L) | 1,600 mL | 400 mL |
Treatment liquid depth in buckets only needs to be approximately 10 cm. Solutions may be reused for up to 3 days if kept clean and refrigerated.