Inkjet Printing Viscosity and Why It Matters

Inkjet printing is one of the most popular and versatile printing technologies on the market today. Industrial-grade inkjet printers, such as continuous inkjet (CIJ) printers and thermal inkjet (TIJ) printers, are used across numerous industries to mark products and product packaging with important codes and messages, including:

  • Date codes
  • Lot codes
  • Serial numbers
  • Barcodes
  • QR codes
  • UDI codes
  • Required product warnings
  • Product use instructions

Many companies also utilize TIJ units and high-resolution (hi-res) case coders (another form of inkjet technology) to outfit their products and shipping containers with large images and messages, such as brand logos, infographics, shipping instructions, and product information. 

Because different industries have unique application requirements, CIJ, TIJ, and hi-res printer formulas must be diverse. Between different ink options, viscosity is one of the main properties that change from formula to formula.

 In this blog, we explore inkjet printing viscosity, explain its importance, and discuss how it affects application suitability.  

Inkjet Printing Viscosity 101

Viscosity is an important ink property because it significantly influences how a formula will react to the printing process. Put simply, “viscosity” refers to how thick fluids are. Scientifically, “viscosity” measures a fluid’s flow resistance and how easily it moves. 

When fluids are in motion, their molecules experience friction. Thicker fluids experience a higher level of friction because their molecules are more strongly attracted to each other. This high friction level causes fluids to move slowly, while fluids with lower friction levels move quickly. For everyday examples, you can think of honey as a high-viscosity fluid and water as a low-viscosity fluid. 

Fluid viscosity is influenced by many factors, including the fluid’s molecular properties as well as environmental elements. Common factors include:

  • Molecule size and complexity (larger size = higher viscosity)
  • Particle concentration (higher concentration = higher viscosity)
  • Ambient temperature (lower temperature = higher viscosity)
  • Flow conditions (e.g., the speed and direction of the fluid’s flow)
  • Pressure (higher pressure = higher viscosity)

So, how does viscosity affect inkjet printing? 

All inkjet printers create markings by propelling tiny ink droplets toward a substrate. These droplets must be uniform in both size and shape to create high-quality codes, images, and markings. This uniformity is only possible if the fluid itself has the right viscosity level.

Viscosity Differences Between Continuous Inkjet, Thermal Inkjet, and Hi-Res Case Coder Ink Formulas

Different inkjet technologies stratify ink in unique ways. The two most common methods are:

  1. Piezoelectric stratification, used by CIJ printers and hi-res case coders
  2. Heat application, used by TIJ printers

In this section, we will examine these two approaches to see the importance of inkjet printing viscosity. 

Piezoelectric Stratification and Inkjet Printing Viscosity 

Piezoelectric stratification is performed at the printhead of CIJ and hi-res printer models. The term “piezoelectric” has two roots:

  • “Piezo,” meaning “to press” or “to squeeze” in Greek, and
  • “Electric,” meaning to generate electricity. 

The term “piezoelectric” refers to materials that generate electricity when exposed to mechanical pressure and change shape via mechanical energy when exposed to electricity. To understand how a piezoelectric printhead works, the main thing you need to know is that piezoelectric elements contract when electrified. 

Within every piezoelectric printhead is a piezoelectric crystal. When a CIJ printer or hi-res case coder is ready to mark a substrate, the printer system electrifies the crystal, causing it to contract and force ink droplets from the printer’s nozzle. The voltage level influences how large the droplet is, enabling users to create either small droplets for faster printing or larger droplets for higher-quality codes. 

CIJ ink is generally less viscous than hi-res ink because CIJ printers are designed for high-speed coding. CIJ units like the DuraCode Touchscreen and DuraCode Pigment print at speeds of up to 330 m/min without interruption, making them ideal for high-volume applications such as printing on:

To complete these various applications, CIJ ink manufacturers create diverse formulas that are suitable for different materials and carry unique properties. InkJet, Inc., for example, carries a wide range of CIJ-compatible inks, including aftermarket replacements and specialt formulas. 

Compared to CIJ ink, hi-res case coders use thicker, more viscous inks to create higher-quality images on porous substrates. Case coders like the Precision Series 72mm are most frequently used to mark shipping cartons with important information, images, and machine-scannable markings, so high-quality images are a must. 

Heat Application and Inkjet Printing Viscosity 

Instead of piezoelectric printheads, thermal inkjet printers like the Anser X1 use heating elements to pressurize ink and create droplets. By manipulatingheat levels and timing heat exposure, TIJ printers can precisely control droplet size and velocity, enabling users to reliably create high-quality images and codes. 

TIJ ink is slightly more viscous than CIJ ink to better respond to the heating elements. Due to their different ink qualities and operating principles, TIJ printers are often slower than CIJ printers but can create higher-quality codes and images. For example, the Anser X1 can create codes at 600 x 600 DPI, while most CIJ printers max out at resolutions far below that. 

In general, TIJ printers are well-suited for companies that are looking for a cost-effective marking solution that delivers high-quality results, is easy to maintain, and doesn’t necessarily need to complete high-speed applications. Although higher-end TIJ models like the X1 can mark materials at speeds of up to 300 m/min, most TIJ models max out at around 120 m/min. 

InkJet, Inc. is Your Source for High-Quality Printer Fluids

Viscosity is just one of the many important properties that ink developers consider when creating formulas. Along with factors like surface adhesion, pigment/dye choice, and dry time, ink manufacturers like Inkjet, Inc. manipulate the viscosity of their formulas to create inks that are ideal for specific applications. 

At InkJet, Inc., we have been creating and selling high-quality printer fluids for more than 30 years. Our diverse offerings include affordable aftermarket cartridges, specialty inks, makeup, and more. If you are interested in switching inks or have questions about which formula will best suit your needs, our team is happy to answer your concerns. Call us today to get started.

For more information about inkjet printing viscosity and other important formula properties, contact InkJet, Inc. online or call 1(800) 280-3245.