The foundation of offset printing lies in the repellent principle between oil-based ink and water-based dampening solution. Translating this principle into a stable press production process requires precise control of the water-ink balance. Imbalances account for 70% of press issues like scumming, slow drying, excessive dot gain, and emulsification. In this technical guide, we examine fount pH, conductivity, and isopropyl alcohol (IPA) parameters.
01Fountain Solution pH and Its Significance
The pH of the dampening solution directly controls the cleanliness of the non-image areas on the plate. The ideal fount pH range is 4.8 to 5.5 (acidic). A pH below 4.8 slows down ink drying (oxidation), wears out the protective layer of the printing plate, and causes metal corrosion. A pH above 5.5 causes the fount to mix easily with ink (emulsification), leading to flat prints and scumming.
Water hardness affects pH stability. The ideal water hardness for offset printing is between 8 and 12° dH (German hardness). Very hard water shifts pH to alkaline, while very soft water increases emulsification risks.
02Conductivity (µS/cm) Monitoring
Conductivity measures the amount of dissolved ions, indicating water purity in microsiemens (µS/cm). A freshly prepared fount solution should have a conductivity of 800 - 1500 µS/cm. As printing progresses, calcium carbonate from paper, ink solvents, and dust dissolve into the water, raising conductivity. When it exceeds 2500 µS/cm, the chemical structure is compromised, leading to color fluctuations. At this stage, the water must be drained and replaced.
03Reducing Isopropyl Alcohol (IPA) and IPA-Free Printing
Isopropyl Alcohol (IPA) reduces fount surface tension, enabling plate wetting with a thin water film. However, high IPA volatility threatens operator health and generates VOC emissions. Modern environmental regulations target lowering IPA levels to 3-5% or achieving 100% alcohol-free (IPA-free) printing. This transition requires advanced fount additives containing surfactants and precise cooling unit calibration (water temperature 10-12°C).
04Frequently Asked Questions (FAQ)
How does dampening water temperature affect printing? Water temperature in the circulation tank should be kept at 10-12°C. Higher temperatures accelerate alcohol evaporation, lower viscosity, and soften ink, increasing emulsification risks. Stable temperature control is a prerequisite for color consistency.
Gallery
Related Products
SIM Baskı Malzemeleri
Get a Custom Quote for Your Project
Contact us for information about our wide product range and custom color production.
