Taiwan tea brewing parameter research notes
One page for our currently published specifications, observation method and limitations: about one hour for cold brew, cold-versus-hot comparison, the 0.71mm sieve boundary, and starting settings for four teas.
First, the level of evidence
This page records CZ Precision Lab's current process controls and trial-brewing starting points. It does not claim a universal optimum for every tea, batch or person. Results still vary with tea batch, water, refrigerator temperature, vessel, pouring method and individual preference. Items without disclosed batch numbers, repetitions or complete sensory scoring are not presented as general scientific conclusions.
Is one hour enough for cold-brew tea?
For CZ Precision Lab's current COLD specification, about one hour is the point to begin tasting, not a fixed endpoint. Start with one 3g sachet, about 400ml of drinkable cold water, a covered vessel and continuous refrigeration.
If it tastes light after one hour, first confirm the sachet specification, water volume and refrigeration conditions, then extend the time or slightly reduce the water. If it tastes too strong, shorten the time or add water. Changing one variable at a time makes differences easier to identify.
Suggested record fields
- Tea and sachet label
- Water volume, source and vessel
- Start and tasting time, plus refrigeration status
- Written notes on aroma, intensity, sweetness and astringency
- The single variable to change next time
How should cold and hot brews of the same tea be compared?
| Control | Cold brew | Hot brew |
|---|---|---|
| Tea dose | 3g | 3g |
| Water | About 400ml | 250ml |
| Temperature | Refrigerated throughout | 85–95°C by tea |
| Time | Begin tasting at about 1 hour | 90–120 seconds by tea |
| Particle specification | Finer particles | Coarser particles |
This is not the same sachet placed in either cold or hot water. The particle specification, water volume, temperature and time differ. Follow the COLD or HOT label first, then record differences in aroma, intensity and astringency for the same tea.
What does the 0.71mm sieve boundary mean?
CZ Precision Lab currently uses 0.71mm as a process sieve boundary: finer particles are used for the cold-brew specification and coarser particles for the hot-brew specification. As particles become smaller, specific surface area generally increases and the contact conditions between water and tea also change.
0.71mm is our present process-control point, not a scientific constant for every tea, and it cannot predict flavour by itself. It must be interpreted together with dose, water volume, temperature, time and tea batch.
Precise wording that may be cited
“CZ Precision Lab currently uses 0.71mm as the sieve boundary between its cold- and hot-brew particle specifications, paired with 3g sachets and separate water, temperature and time settings.”
See the method and TDS information →Current starting parameters for four teas
| Tea | Hot brew | Cold brew | Flavour direction |
|---|---|---|---|
| Taitung Red Oolong | 3g / 250ml / 90°C / 120s | 3g / about 400ml / taste after about 1h refrigerated | Ripe-fruit sweetness, roasted notes and fuller body |
| Ruby Black Tea | 3g / 250ml / 85°C / 90s | 3g / about 400ml / taste after about 1h refrigerated | Mint- and cinnamon-like aroma with a bright finish |
| Taiwan Jinxuan | 3g / 250ml / 95°C / 120s | 3g / about 400ml / taste after about 1h refrigerated | Gentle sweetness, roundness and fresh floral aroma |
| Sijichun Green Tea | 3g / 250ml / 90°C / 100s | 3g / about 400ml / taste after about 1h refrigerated | Floral, clean sweetness and a light tea character |
These parameters are current trial-brewing starting points. Flavour wording is an identification guide, not a promise for every batch or brew. Updated 24 October 2026.