Free tools for winemakers
Bench trial calculator
From a bench sample to the whole volume
Dose rate
Type the stock strength, the mL added and the sample size.
Amounts for the full volume appear once you type the volume to treat.
Check the copper limits.
Grams of product per 100 mL of solution.
How do we calculate this?
The exact formulas used in this tab:
What this calculator does
Scales a bench trial up to the cellar. From the stock solution and the sample, it gives the dose rate in g/hL and mg/L, and the grams of product, or mL of the same stock, for the whole volume.
- Type the strength of your stock solution as % w/v (grams of product per 100 mL), how many mL of it you added and how big the sample was.
- Add the volume to treat to get the amounts for the whole volume.
- Presets fill in typical strengths for bentonite, copper sulfate, tannin and gelatin.
- For copper sulfate it also shows the copper concentration it adds to the wine and warns at the legal limits.
The formula
Strength (% w/v) = grams of product per 100 mL of stockProduct in the sample (g) = strength × stock added (mL) ÷ 100Rate (mg/L) = product in the sample (g) × 1,000,000 ÷ sample (mL)Rate (g/hL) = mg/L ÷ 10Product for the full volume (g) = g/hL × volume L ÷ 100Stock for the full volume (mL) = stock added (mL) × volume L × 1000 ÷ sample (mL)Copper (mg/L) = copper sulfate (mg/L) × 0.254 (CuSO₄·5H₂O is 25.4% copper)Source: AWRI, "Conducting a bentonite fining trial" (1 mL of a 5% slurry in 100 mL = 500 mg/L)
Worked example
- Bentonite slurry: 5%
- 1 mL of it in a 100 mL sample
- 1,000 L of wine to treat
- Bentonite in the sample 5 × 1 ÷ 100 = 0.05 g
- Dose rate 0.05 × 1,000,000 ÷ 100 = 500 mg/L
- The same rate in g/hL 500 ÷ 10 = 50 g/hL
- Bentonite for the whole volume 50 × 1,000 ÷ 100 = 500 g
- Or slurry for the whole volume 1 × 1,000 ÷ 100 = 10 L
Add 500 g of bentonite, or 10 L of the same slurry
Questions
What does % w/v mean?
Weight per volume: grams of product in every 100 mL of solution. A 5% slurry is 5 g of bentonite made up to 100 mL with water. Made up to, not added to, so the final volume is 100 mL.
How much copper does copper sulfate add?
Copper is 25.4% of the weight of copper sulfate pentahydrate (CuSO₄·5H₂O). So 0.1 mL of a 1% solution in 100 mL is 1 g/hL of the salt and 2.54 mg/L of copper. That is already past the US limit of 0.5 mg/L left in the finished wine and the EU’s 1 mg/L. That is why copper trials dilute the 1% solution further.
US: 27 CFR 24.246. EU: Regulation (EU) 2019/934.
Does the stock I add change the sample volume?
A little, and the calculator leaves it out, as the AWRI method does: the rate is worked out on the sample before the stock goes in. With 1 mL in 100 mL the difference is about 1%, far smaller than the steps between the rates a bench trial compares.
Does it tell me which dose to use?
No. Run a series of samples at different rates, pick the lowest one that does the job, and type that one in. The calculator only scales it up.
Guides that use this calculator
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How much bentonite? Protein stability in white and rosé wine
White and rosé wines usually need 10–100 g/hL of bentonite, but only a bench trial and an 80 °C heat test tell you how much. Run one, then scale up.