Scope of this guide
This intermediate guide goes into diagnosis: reading symptoms, isolating the variable that changed, and fixing it with data you can collect on the line.
Process: Cold Painting. Figures in this guide are industry-standard starting ranges; confirm against your supplier TDS before locking settings.
Working ranges and control points
The table below is the daily reference for a cold spray bench. Set by the card, verify by the control point column.
| Parameter | Typical range | Control point | Watch out |
|---|---|---|---|
| Thinner ratio | 5–15% by volume | Viscosity cup per batch | Over-thin low build |
| Air pressure | 2.5–4 bar | Regulator locked | High pressure overspray |
| Coat count | 2–3 light coats | Dry-touch between coats | Heavy single coat sags |
| Dry time, ambient | 20–40 min per coat | Finger-drag test | Stacking too early prints |
| Colour check | Standard card under D65 + A light | Metamerism screen | Match fails indoors only |
Diagnose It Fast: the intermediate view
Beyond the basic card, this is the layer that matters at your level:
| Symptom | Likely variable | Confirm by | First fix |
|---|---|---|---|
| Dull or hazy finish | Bath chemistry drift | Hull cell panel | Rebalance per test |
| Defects cluster on one rack position | Contact or current map | Position thickness map | Repair contact / re-map amps |
| Good-bad-good pattern | Loading or cycle drift | Time-stamped samples | Standardise load weight |
| Defect appears after maintenance | Work just done | Revert one change | Restore and re-verify |
Standard routine
- Match colour under two light sources before production
- Filter paint through 120 mesh
- Keep bench drafts off while spraying
- Dry-touch between coats, full dry before pack
- Sign the colour standard card per batch
Engineer notes
- Metamerism is the classic cold-paint reject — check under shop and daylight lamps
- Cold booths need warmer thinner ratio in winter
- Small parts on wire stands show shadow lines — rotate stands 180° between coats
- Record batch numbers; colour claims trace to them
- Old paint absorbs moisture — filter twice and test on scrap
Safety: Spray mists carry isocyanates in some 2K paints. Use supplied-air or A2P respirators for 2K products; skin contact needs barrier cream.
FAQ
Why does colour match in the booth but fail at the customer?
Metamerism. Approve colour under both D65 and warm light before production.
Can I speed drying with heat?
Mild warmth 40 °C is fine; hot air skins the coat and traps solvent.
How much thinner should I add?
To viscosity, not volume: target the cup seconds on the paint card, 16–22 s typical.