Excessive emulsification of offset ink is one of the most common technical problems encountered in print shops. The symptoms appear quickly: washed-out colors, unstable density, toning (scumming of the non-image areas), slow drying in the stack, set-off and build-up on the offset blanket. Even so, the cause is not always the same, and treating the symptoms without a correct diagnosis leads to wasted time, more waste sheets and unnecessary consumption of materials.

 

This guide explains what excessive emulsification is in offset printing, how it can be correctly diagnosed, what immediate interventions are recommended and how it can be prevented over the long term through the appropriate choice of fountain solution and printing ink.

1. What is emulsification in offset printing and when does it become a problem?

Offset printing works on the principle of mutual repulsion between water and ink. The non-image areas of the printing plate are hydrophilic and attract water, while the image areas are oleophilic, repel water and accept ink.

A certain level of ink emulsification is always present in the printing process. It is inevitable and represents a normal operating condition. The acceptable degree of emulsification differs depending on the type of ink, the dampening system, the printing speed and the production conditions.

The problem arises when emulsification becomes excessive. In this situation, the ink takes up too much water, and the ink vehicle loses its ability to split and transfer properly between the rollers, plate, blanket and substrate. As a result, ink transfer deteriorates, color stability decreases, and the printing process becomes difficult to control.

Clear signs of excessive offset ink emulsification

• Optical density drops, even though the amount of ink laid down increases.
• Dull, washed-out colors, lacking saturation, especially on magenta and cyan
• Toning: scumming in the non-printing areas 
• The ink in the duct takes on a milky or foamy appearance
• Slow drying in the stack, risk of set-off onto the reverse
• Build-up on the printing blanket (piling)
• Ghosting: local density variations or shadows in the image, caused by imbalances in ink transfer and the fountain solution
• Color instability throughout the print run, with the first sheets differing from those in the middle

Note: Excessive emulsification and stripping (poor ink transfer caused by uneven distribution of water in the roller train) can produce partly similar symptoms — unstable colors and dirt on the plate. A correct diagnosis before any intervention is essential. For technical support or help with diagnosis, contact us at contact@printman.ro.

2. The causes of excessive offset ink emulsification: where the problem comes from

a) Too much water in the dampening system

The most common cause. The operator increases the fountain solution to clean toning off the plate, but the excess water enters the ink system and destabilizes the ink-fountain solution balance. The basic rule in offset: use the minimum amount of fountain solution that keeps the non-image area clean. Any surplus beyond this minimum is a potential source of excessive emulsification.

b) Incorrect fountain solution pH

The optimal pH value for offset fountain solution is around 4.8–5.5. Below 4.5, the solution becomes too acidic, attacks the offset plate  and destabilizes the ink. Above 5.5, the stability of the non-printing areas decreases and the risk of toning and instability increases. The pH drifts over the course of a long run due to interaction with the paper (calcium ions from the coating layer are the main contaminant), the ink and dust particles. Regular monitoring is essential for the stability of the printing process.

c) High conductivity of the fountain solution

The conductivity of the solution rises progressively over the course of production due to contaminants: paper dust, ink particles, calcium and magnesium ions. A significant increase compared with the conductivity of the freshly prepared solution indicates contamination and the need for replacement. As a reference value frequently used in practice, a conductivity above 1,000 µS/cm is a warning sign — the exact threshold, however, depends on the quality of the local water and the additive used. A recirculation system without adequate filtration accelerates this degradation.

d) Worn or fouled dampening or inking rollers

Rollers fouled with a surface layer of limescale, polymerized ink or deposits from the fountain solution no longer distribute the fountain solution and ink evenly on the plate. The result is an uneven distribution of water, with overloaded zones that promote local emulsification. Periodic cleaning of the rollers is a preventive maintenance operation with a direct impact on the stability of the ink-fountain solution balance.

e) Printing ink with low resistance to the fountain solution

Not all offset inks have the same tolerance to the fountain solution. An ink with too low a viscosity or without specific stabilizers for the ink-fountain solution balance emulsifies faster and with more severe effects. This is why replacing an ink with a cheaper one sometimes produces printing instability problems that did not exist before.

f) High temperature at the printing unit

Warm ink becomes more fluid and takes up more water. The optimal temperature at the printing unit is 20–25 °C. Pressrooms without air conditioning or high-speed presses without roller cooling are more prone to excessive emulsification during hot periods.

g) IPA outside the correct parameters

Isopropyl alcohol (IPA) reduces the surface tension of the water and helps form a uniform dampening film on the plate. At too high a concentration (>15%), IPA can destabilize the ink and accelerate emulsification. At too low a concentration, relative to the amount of water, the dampening film becomes uneven. The correct concentration depends on the dampening system, the type of additive and the water quality; there is no universal value.

h) The paper: an often ignored factor

Alkaline paper (pH >7) or paper with an unstable coating layer releases calcium ions and particles into the fountain solution, increasing conductivity and destabilizing the pH during the run. Paper with low pick resistance releases fibers and particles that contaminate the solution. If emulsification consistently occurs on the same type of paper and not on others, the source may well be a property of the substrate itself.

3. Rapid diagnosis on the press: what to measure and in what order

If you want to start the diagnosis on your own, you can use these measurements as a starting point. And if you need help or technical support along the way, you can contact us any time at the email address contact@printman.ro or directly here, on our website.

First of all, measurement is the first step with which we begin the technical diagnosis. Any intervention without measurement data is a correction with an equal chance of making the problem worse or of solving it.

 

Minimum investment: a combined pH + conductivity tester (e.g. Hanna HI98129) is the basic instrument for any offset print shop. Without these two measurements, diagnosing the ink-fountain solution balance is almost impossible to do objectively.

4. Immediate interventions on the press: 5 steps in order of priority

Step 1 — Gradually reduce the amount of water

As a rule, this is the first intervention to try. Reduce the fountain solution flow by about 5–10% from the current setting and watch how the density and plate cleanliness evolve. Objective: the minimum amount of water that keeps the non-image area clean. Do not reduce abruptly and do not eliminate the water completely.

Step 2 — Check the pH and conductivity

If the pH is outside the 4.8–5.5 range, adjust the concentration of the dampening additive. If the conductivity has increased significantly compared with the value of the fresh solution, replace the fountain solution completely — a fresh preparation with water and additive at the recommended concentration.

Step 3 — Assess the ink in the duct

If the ink has a milky, foamy appearance or has lost its normal consistency, the emulsification has reached the duct. As a rule, the only effective remedy at this stage is to stop the press, wash the ink train completely (rollers + duct), add fresh ink and restart with minimum water. Do not try to "save" the emulsified ink by adding new ink on top of it.

Step 4 — Control the temperature

If the temperature at the printing unit exceeds 28–30 °C, reducing the speed or activating roller cooling (if the press allows it) can stabilize the emulsion. Over the long term, air conditioning of the pressroom is the only durable solution.

Step 5 — Check the pressures and the condition of the rollers

Incorrect pressures between the rollers and the plate or between the inking and dampening rollers create local zones of excessive water. Check the contact stripes (with carbon paper) and compare them with the press manufacturer's specifications. Glazed rollers must be cleaned or replaced.

If the problem persists after these steps: the cause is most likely an incompatibility between the ink and the dampening additive, or an ink with insufficient water resistance. Contact your consumables supplier with the data: press type, additive used, IPA concentration, water hardness, current ink and the exact symptoms.

5. Offset dampening additives: the Printman products and when to use each

The correct dampening additive is the most effective preventive tool against excessive emulsification. A good additive stabilizes the pH throughout the entire run, ensures a uniform dampening film on the plate and keeps the ink-fountain solution balance within controllable parameters, regardless of variations in paper, speed or ambient temperature.

Sheetfed offset presses: fountain solutions

Fountmax Blue 30.11 — formulated for modern CTP systems and sheetfed presses, with 8–12% IPA. Recommended for all types of water (soft or hard). Dosage 2–3%. Compatible with conventional and UV inks. Ensures a stable pH of 4.8–5.5, a stable ink-water balance and consistent print quality, without excessive emulsification.

Fountmax Blue 30.33 AF — for reducing IPA to 0–8%, including completely alcohol-free printing. Dosage 3–4%. In addition to preventing emulsification: reduced VOCs, improved working conditions, savings on IPA cost, fewer stoppages and higher productivity.

Supreme Varn — a pH-regulating additive for sheetfed presses, recommended for water with a hardness below 15 German degrees. It provides cleaner and faster press starts, with a clear reduction in ink consumption. ISEGA certified. Dosage up to pH 4.8–5.5.

Supreme 250 Varn — the same Supreme range, but formulated for water with a hardness above 15 German degrees. The choice between Supreme and Supreme 250 is made exclusively according to the hardness of the local water.

Varn SFF 9275 — a new-generation additive for advanced reduction or complete elimination of IPA. Stable in any water quality. Compatible with all types of offset plates, inks and dampening systems. It provides sharper printing, a clean start, is biodegradable and inhibits corrosion.

Varn Ultra 4100 — formulated specifically for printing with UV, LED-UV and H-UV inks, but also compatible with conventional inks. It provides gentler dampening to reduce the emulsification specific to UV inks, which have a narrower tolerance to water. ISEGA certified.

Heatset web presses

Varn HSF 9209 — formulated for high-speed heatset web presses. It allows the reduction or complete elimination of IPA. Fast start-up to ink-water balance, reduced downtime and fewer blanket washes. Flash point >100 °C, for safer storage and handling.

Sunday Fount Varn — specially formulated for the demanding requirements of high-speed heatset web presses. Compatible with negative and positive CTP plates. An extremely clean solution, it minimizes ink returning into the recirculation tanks. It can completely eliminate IPA. It reduces start-up waste, with proven performance at speeds above 15 m/s.

Coldset web presses

Journal Fount SEW-D Varn — an additive for coldset web presses with brush and spray-nozzle dampening systems. It works with less water and ink, provides an extremely fast and clean start-up, a stable pH system, advanced anti-corrosion technology, CTP compatibility and OEM approval.

Auxiliary: against foam in the dampening system

Antifoam — used against foam formation in the dampening system. Foam in the solution tank is a sign of contamination or of an incorrect additive concentration. Antifoam treats the immediate symptom; the cause (degraded solution or wrong concentration) must be addressed separately.

6. Offset printing ink and water resistance: what matters

If excessive emulsification consistently occurs at the same printing unit, with correct fountain solution parameters, the cause may be the printing ink. Inks with low water resistance or too low a viscosity emulsify more easily and with more severe effects.

Properties to look for when choosing an offset ink

• Good resistance to the fountain solution: the ability to repel the fountain solution without excessive absorption
• Stability in the duct (duct fresh): ink that emulsifies in the duct overnight has insufficient water resistance
• Low dot gain: a stable halftone dot reduces the need for repeated adjustments that generate waste sheets
• Confirmed compatibility with the dampening additive used on your press

Flint Group inks from the Printman catalog with good resistance in the ink-water balance

Novavit 950 Fauna — is a high-performance ink based on renewable raw materials (BIO quality), designed for high printing speeds and multicolor presses. It is optimized for coated paper and board, gloss or matte, but also works excellently on uncoated substrates. It complies with the ISO 2846-1 standard and is suitable for printing according to ISO 12647-2. The duct fresh formula prevents drying in the ink duct, while the advanced binder system improves the stability of the ink-water balance and reduces misting at high speeds. It provides fast setting, superior rub resistance and high halftone dot sharpness. 

Novasens P670 Prime — a high degree of pigmentation, allowing printing with a minimal ink film. Fast setting and good performance with subsequent varnishing. ISEGA certified, compliant with EU 1935/2004.

Novavit F700 Speed Bio —  a vegetable-oil-based ink, made from renewable raw materials (BIO quality), recommended for printing on coated and uncoated substrates that require fast processing. It is suitable for printing according to the ISO 12647-2 standard, stays fresh in the ink duct overnight (duct fresh), provides very good rub resistance and can be used at high printing speeds. 

NAKA K-Supply — vegetable-oil-based, with over 70% renewable raw materials. Duct fresh, suitable for any type of substrate. Fast drying and setting. Color standardization according to ISO 12647-2. Also usable on presses with a perfector.

Novaboard 1090 Race Bio — high pigmentation, fast drying and high rub resistance. Low tack and a high degree of gloss. Suitable for high speeds and presses with a perfector. Recommended for paper and board of all types.

7. Roller maintenance: cleaning as a preventive tool

Fouled rollers are a frequently ignored cause of excessive emulsification. The build-up of a hard layer of limescale, polymerized ink or residues from the fountain solution changes the hardness of the roller surface and the uniform distribution of ink and water on the plate.

Pur-O-Past — a paste for cleaning and reconditioning the rubber rollers of offset presses. It cleans deeply and removes limescale deposits from the rollers, originating from paper and fountain solution. Used during washing when switching from a dark color to a light one.

Walzenreiniger 6001 — a paste for cleaning and reconditioning rubber rollers. It has the same purpose as Pur-O-Past, being an alternative option for the same type of application.

MRC-LO — a strong degreasing solution for rubber and chrome dampening rollers, where fast evaporation is required. A universal product for the deep cleaning of the rubber rollers of printing presses.

The recommended cleaning frequency depends on the production volume and the water quality. As a general reference: monthly or every 500,000 sheets, whenever the rollers show visible signs of changed hardness or uneven distribution.

8. Long-term prevention: the routine that eliminates the problem before it appears

Systematic monitoring of the fountain solution

• Measure the pH and conductivity at the start of each shift
• Change the fountain solution at most every 14 days, more often at high volumes
• Record the values. Variations over the run indicate whether the paper or the ink is contaminating the solution
• Check the raw water hardness at the source. A hardness >15 German degrees requires an additive formulated for hard water

Preventive roller maintenance

• Periodic  cleaning with Pur-O-Past, Walzenreiniger 6001 or MRC-LO
• Checking the contact pressures at every major job change
• Replacing rollers with changed hardness. A roller that is too hard or too soft changes the transfer of water and ink

Calibration of the dampening system

• Keep the solution temperature at 10°C if the press has a cooling system
• Check the recirculation filters. A clogged filter reduces flow and creates uneven distribution
• When switching to IPA-free printing, the press adaptation process takes several weeks and must be done gradually, not abruptly

Frequently asked questions about offset ink emulsification

What pH should the offset fountain solution have?

The optimal value is 4.8–5.5. Below 4.5, the solution is too acidic and attacks the plate; above 5.5, the stability of the non-printing areas decreases and the risk of toning and instability in offset printing increases. The pH drifts over the course of the run due to contaminants, and monitoring at every shift is recommended as standard practice.

Why does the ink density drop over the course of the run, even though I haven't changed anything?

The most common reason is the progressive degradation of the fountain solution: the conductivity has risen (limescale from the paper, calcium ions from the ink), the pH has drifted, and the ink-water balance is no longer maintained. The ink gradually emulsifies more and more, and transfer decreases. Solution: completely replace the fountain solution and recalibrate the additive.

How do I know if the ink in the duct is emulsified and needs to be changed?

The clear visual sign: the ink has a milky, foamy appearance or a texture that has changed from its initial state. The simple test: take a sample on a spatula. Emulsified ink is more fluid, lighter in color and loses its gloss. At this stage, a complete wash of the unit and replacement of the printing ink are the only correct solutions.

What dampening additive do you recommend for my sheetfed offset press with 10% IPA?

Fountmax Blue 30.11 and Supreme Varn are all formulated for 8–12% IPA on sheetfed presses. The correct choice additionally depends on the hardness of the local water: below 15 German degrees, Supreme Varn; above 15 German degrees, Supreme 250 Varn . Contact the Printman technical team with your water pH and hardness values for a precise recommendation.

Emulsification appears only on Magenta and Cyan, not on Yellow and Black. Why?

Certain pigments used in Magenta are more sensitive to calcium contamination and pH variations than the pigments used in Yellow and Black. If the problem is localized on certain colors, check the pH first — a value below 4.8 can disproportionately affect Magenta — as well as the specific compatibility of the ink with the additive used.

Do you have recurring emulsification and haven't identified the cause?

If the problem keeps recurring, even after standard adjustments, the cause is usually more complex: an incompatibility between the ink and the dampening additive, water with unsuitable hardness, contamination of the solution or unstable press parameters.

The Printman technical team can analyze the specific situation in your print shop based on real production parameters: the press type, the pH and conductivity values, the IPA concentration, the type of ink and its behavior during the run. The goal is not just to recommend a product, but to identify the real cause of the instability in the offset process.

For technical support or personalized recommendations, you can contact us at contact@printman.ro or directly at printman.ro.