Sizu Riatto
Flush Hour · Chapter 2

Wet and Dry

Get the water right and the rest of the grow follows. Follow the dry stuff: it never changes, so one oven test tells you what the soaked straw should weigh before you soak it.

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Opens on the book's tub. Change any number to your own and press Calculate.

The oven test: weigh a sample, dry it, weigh it again

The straw and the target

Check the drained straw: oven-dry a sample of it

Enter the oven test and the straw's weight, then press Calculate.

The formula

  • Moisture, wet basis = water ÷ (water + dry matter) × 100; the oven test: (before − after) ÷ before × 100
  • Dry matter = weight × (1 − moisture ÷ 100): it stays the same however wet the straw gets
  • Weight at a target = dry matter ÷ (1 − target ÷ 100)
  • Water taken up = the wet weight − the weight as bought
  • Dry basis = water ÷ dry matter × 100 = wet basis ÷ (100 − wet basis) × 100: 70% wet basis is 233% dry basis
The book's worked example, Chapter 2. The oven test takes 100 g of straw to 90 g: 10% water. So 2.0 kg as bought holds 1.80 kg of dry matter and 0.20 kg of water. At 70% it weighs 1.80 ÷ 0.30 = 6.0 kg (13.23 lb), holding 4.2 kg of water; it takes up 4.0 kg. On a dry basis that is 233.33%. The drained sample checks it: 200 g dries to 60 g, 70%.
Check it. Before the oven, call the moisture of a drained handful: a hard squeeze that gives a few drops is the feel test; the oven and the scale are the real one.

Honest limits. A home oven or a dehydrator may not hold 103 to 105 °C, the lab's drying temperature, so a home oven test is an estimate: dry until two weighings an hour apart agree. Straw varies bale to bale; test each bale. The book's tub, its straw and its harvests were worked out on paper from published figures, not grown by us: weigh your own. Prices are illustrative, as seen in November 2026 (US mid prices, with UK beside where they differ), shown without a currency sign; put in your own. No yield or profit is promised. Everything stays in your browser: no sign-up, nothing stored.