The parent’s 6-8 weeks of peat drying is a guide, not a measurement; the way to know a block is ready is to weigh it. Weigh three marked blocks weekly, find the dry mass of a matching sample by drying it fully, and calculate wet-basis moisture as one minus dry mass over current mass; the peat is ready at 30% or below.
Part of Peat Harvesting
Tracking peat drying week by week by weighing sample blocks, and turning the weights into moisture figures.
A Block Dries From The Outside In
A crust forms in a week or two, while the inside stays wet. Hand tests (weight, hardness, a dull knock) are quick, but they only read the outside. The scale reads the whole block. The parent states the target as below 30% moisture, a wet-basis figure (water as a share of total mass).
What You Need
- A scale that reads to 10 g or better and holds a block
- Three marked sample blocks, cut from the same layer as the rest and kept with the batch
- A way to dry a sample completely: a stove-top or oven at about 100-105 °C, with the sample weighed repeatedly until the mass stops changing
- A notebook (Record Keeping)
Method
Step 1: Fresh mass. Weigh each marked block when cut and record the date.
Step 2: Find dry mass. Take a similar piece from the same cut, weigh it, dry it fully and weigh it again. Dry fraction = dry mass ÷ fresh mass. Multiply by each marked block’s fresh mass to get its dry mass.
Step 3: Weigh weekly. Moisture (wet basis) = 1 − dry mass ÷ current mass.
Step 4: Plot it. Mass falls fast at first and then slows. The block is ready when moisture reaches the 30% target and two weekly weighings agree.
Worked Example
Inputs: fresh block 3.00 kg; the matching sample shows a 10% dry fraction, so dry mass = 3.00 × 0.10 = 0.30 kg (an invented example, not a measurement).
| Week | Block mass (kg) | Moisture = 1 − 0.30 ÷ mass |
|---|---|---|
| 0 | 3.00 | 90% |
| 2 | 1.60 | 81% |
| 4 | 0.90 | 67% |
| 6 | 0.55 | 45% |
| 8 | 0.45 | 33% |
| 9 | 0.43 | 30% |
The target mass is 0.30 ÷ (1 − 0.30) = 0.43 kg, so the block is ready at week 9 in this invented example, a week later than the parent’s top of 6-8 weeks. A wet summer would add more.
Common Mistakes
- Reading moisture from the surface. The crust dries first.
- Not drying the control sample. Without dry mass the weights say nothing about moisture.
- Mixing bases. A dry-basis figure is larger than the wet-basis figure for the same peat.
Safety
Oven-drying peat is a fire risk
Dry the control sample in a metal tray, in a stove or oven that you watch, at the lowest heat that works. Dry peat smoulders when overheated, and its smoke contains carbon monoxide: ventilate the room.
What’s Next
- Learn next: Burning & Performance — using the dry fuel
- Combine with: Weather Dependency — why the timeline moves