The dampening system is the subsystem most often underestimated by used-press buyers: the recirculator tank, the water rollers and the automatic wash-up devices never appear in impression-pressure checks, yet the moment their parameters drift or a wash unit jams, ink-water balance and press availability collapse together. This guide turns dampening-solution chemistry, conductivity monitoring, impression-cylinder wash-up maintenance windows and wash-device fault codes into a practical checklist for both inspection day and daily upkeep.
- Composition water hardness should sit between 8 and 12 °dH, and the mixed solution should hold a pH of 4.8 to 5.5, stabilized by the buffer agent against ink and substrate contamination.
- Tank temperature must stay below 10–15 ℃: higher water temperature raises conductivity, while higher alcohol content lowers it — always correct the reading for both.
- Conductivity has no universal standard value; record a baseline when the tank is freshly mixed, and a drift of 800–1000 µS/cm or more above baseline means the solution is spent — change the tank instead of topping up.
- On CD102 presses from the Drupa '95 version onward, the impression-cylinder wash-up device (DZW) is standard equipment; service it every six months to a year depending on utilization, roughly 4 hours per printing unit, dismantled by an authorized technician only.
- Wash-device faults are graded by code: yellow warnings abort the wash cycle, orange signals consumables, and a confirmed red fault disables the main drive — clearing them one by one on inspection day exposes the machine's maintenance history.
1. Four hard parameters: hardness, pH, temperature and biological stability
Many shops only watch alcohol percentage, and that is the first mistake. Water hardness comes first: excessive calcium and magnesium bind with solution components and build a calcified glaze on the water rollers; once the form dampening roller is glazed, stable water transfer is gone. Very soft water, on the other hand, is corrosive to pans and pipework. Practice puts 8–12 °dH in the workable band; beyond that, treat the water — reverse-osmosis units remove roughly 95 percent of the mineral content of tap water and remain the standard fix in hard-water regions.
For pH, 4.8–5.5 is the working window after mixing; what matters is not hitting a number once but the buffer's ability to absorb the constant pH drag from ink and paper dust. A weak buffer drifts within a shift, and on the sheet it shows as scumming in the non-image areas with growing ink-in-water emulsification. Temperature is the third line: hold the tank below 10–15 ℃ so alcohol evaporates slowly and the solution film stays thin and even. A properly formulated solution also carries anti-fungal and anti-algae additives; algae films inside a long-untouched tank are the most honest physical evidence of neglected maintenance.
2. Watch conductivity, not just pH: baseline first, drift second
A pH meter tells you acidity, not what has dissolved into the water. Conductivity reflects the total load of conductive contaminants — paper dust, saponified ink, minerals — and rises monotonically in service, which is why it has largely replaced pH as the first daily reference. The procedure is plain: measure a baseline the day the tank is mixed, then check daily; a deviation of 800–1000 µS/cm or more above baseline predicts dampening-related trouble — plate scumming, roller calcification, heavier emulsification — and calls for a full tank change.
Two variables correct every reading: conductivity climbs with temperature and falls with alcohol content. Alcohol's job is to pull surface tension from roughly 72 mN/m for pure water down toward 22 mN/m, so the film spreads thin and even, ink-water balance arrives quickly, and foam and mold are suppressed. When a reading looks wrong, check water temperature first, alcohol percentage second, and only then blame the solution — reversing the order wastes good chemistry or stretches bad chemistry another week.
3. The impression-cylinder wash-up device: a six-to-twelve-month window
Buyers check whether an automatic wash-up device is fitted, rarely whether it still turns. Take the impression-cylinder wash-up device: it sits inside the press base where an operator cannot reach it, so service means dismantling the whole unit with an authorized technician. Depending on utilization, plan a full service every six months to a year; under favorable conditions with no major wear it takes about four hours per printing unit. Service is not just wiping: the brush roller (83 mm diameter), gears, bearings, short-stroke cylinder, spray tubes and valves are each checked for wear and function. One detail separates competent hands from the rest — the two Allen screws in the wall frame must never be unscrewed completely, only loosened; dropping one into the base turns a routine service into a recovery job.
4. Wash-device fault codes: from yellow hint to red stop
On newer control platforms, advanced wash-device faults no longer appear in the wash/status display menu but in the central fault menu, graded by code. Six entries cover most inspection-day situations:
| Code | Meaning | Press reaction | Action |
|---|---|---|---|
| 0x2000022 | Ink roller wash-up device: doctoring blade not fitted | Wash aborted; yellow hint; unit wash program blocked | Check blade fitting and sensor |
| 0x2000023 | Insufficient ink-roller wash-up solution | Press blocked while the wash program runs | Refill wash-up solution |
| 0x2000024 | Blanket wash-up device: cloth at end / cassette missing | Wash aborted; orange hint | Replace cloth or refit cassette |
| 0x2000035 | Blanket wash-up device: cloth feed error | Confirmable red fault; main drive disabled | Check feed sensor and cloth roll, confirm to reset |
| 0x2000824 | Ink roller wash-up device: unit not found | Unit wash program cannot execute | Check presence signal and mechanical locking |
| 0x200010C | Dryer: waiting time before wash-up not elapsed | Press blocked at wash start | Wait for the drying program to finish |
On inspection day do not merely run paper: execute the wash program of every unit. A fault list with red records, or a confirm button that has clearly been pressed countless times, points at an unresolved wash chain. Cloth-level sensors and blade sensors are small parts, yet they can report as a main-drive disabling fault — one of the most common sources of phantom stoppages on older presses.
5. An eight-point dampening checklist for used-press acceptance
Compressed for the shop floor: inspect the tank walls for algae and scale; verify a fresh solution can produce both a conductivity and a pH baseline; read the actual tank temperature against the 15 ℃ line; feel the form dampening roller for glaze and uneven wetting; run each unit's wash program and log the codes; check that cloth, blade and their sensors report honestly; look for rust and weeping at pans and pipes; and on hard-water sites confirm reverse osmosis or softening is installed. Two failures out of eight are enough to move the whole dampening section onto the price-negotiation list.
Two more misjudgments recur. First, roller calcification is blamed on the roller; in most cases the solution ran hard and alkaline for months, and fitting new rollers without fixing the water reproduces the glaze within a quarter. Second, wash-device alarms are treated as mechanical breakdowns; walk the code list through sensors and consumables first, because many stoppages are nothing more than a paper-dust-blinded cloth-end switch. A well-kept dampening system is quiet: steady temperature, a flat conductivity curve, wash programs that pass on the first attempt. For the overall service plan, see our earlier piece on the four-level maintenance window from daily to annual checks, and when the parameters look right, browse the current equipment listings to filter by format and color units.
Conclusion: Dampening maintenance is not about wiping more often — it is about managing quantifiable parameters: hardness 8–12 °dH, pH 4.8–5.5, tank temperature below 15 ℃, a full solution change once conductivity drifts 800–1000 µS/cm above baseline, plus a six-to-twelve-month wash-up teardown and a code-graded fault routine. On the used market these numbers are the best x-ray available: the tank and the wash devices almost never lie.
