Act 5. Scaling and Direct
Scaling the Batch
When one pot stops being enough.
The kitchen batch that works at three vessels does not automatically work at thirty. Wax mass has thermal inertia: a 1.2 kg melt cools measurably faster than a 6 kg melt, so the pour temperature that gave you glossy tops last week gives you sink holes this week. Fragrance-oil dispersion is worse at higher volumes because the stir path is longer. And every extra pour is a chance for temperature drift between the first and last vessel of the run.
Scale in disciplined doublings. If today's proven batch is twelve vessels, the next tested batch is twenty-four, not the fifty you actually want to ship. Every doubling triggers a fresh four-burn protocol on the first and last vessel of the run to prove homogeneity.
Batch-size thermal targets (soy container blend)
- 1–12 vessels (hobby)
- Melt on a bain-marie. Pour temperature 55–60°C, tolerance ±2°C.
- 13–36 vessels (weekend maker)
- Thermostatic melter, 8–12 L. Pour temperature 55–60°C, tolerance ±2°C. Stir at 500 rpm for 2 min after fragrance drop.
- 37–100 vessels (workshop)
- Jacketed melter, 20–30 L. Pour temperature 55–60°C, tolerance ±1°C. Powered stirrer, timed 3 min. Pour within 12 min of fragrance drop.
- 100+ vessels (small-batch production)
- Two jacketed vessels in parallel plus a decanting pot. Pour temperature 55–60°C, tolerance ±1°C. Fill from a levelled decant pot to hold surface finish across the run.
Source:
± 1°C
Temperature tolerance for a workshop-scale melter·
Pre-scale checklist
- Batch doubled, not tripled or quadrupled in one step
- First and last vessel of the run tagged for four-burn protocol
- Melt-to-pour clock recorded, target under 12 min
- Ambient bench temperature logged for the whole run
- Cure shelf capacity confirmed before the pour begins
| Symptom | Likely cause | Fix | Prevent |
|---|---|---|---|
| Frosting appears on the last third of a scaled batch, not the first. | Melter temperature drifted below the target as pour progressed and no reheat was scheduled. | Hold the melter at pour temperature ±1°C with a jacketed vessel or return to the melter between pours; log temperature every 6 vessels. | Schedule reheat checkpoints into the pour plan before starting; use a jacketed vessel or a thermocouple alarm rather than eyeballing. |
| Sink holes appear only on the larger batch size. | Thermal mass of the bigger melt is cooling more slowly, so surface skins before the interior settles. | Drop pour temperature 2°C and pre-warm vessels to 40°C to slow the surface skin; retest the four-burn protocol. | Re-run the four-burn protocol every time batch size doubles; record the pour temperature and vessel pre-warm target on the batch record. |