Density Testing

A fluid inside a glass U-tube will vibrate at a certain frequency depending on the mass and temperature. The measured frequency is compared to known calibration points for accurate results. Density plays an important role in beverage, chemical, petroleum, pharmaceutical and sugar industries. The density of a fluid is an important parameter that is necessary for the application of other measurement techniques and to gain a complete understanding of a fluid’s properties.

Typical Experimental Results

Density and Specific Gravity of Motor Oil at Different Temperatures with Viscosity Correction

Motor oil density vs. temperature

Density of Cyan and Magenta Printer Inks

Applications

For more information please read our application notes:
Density and Surface Tension of Ink, PDF

Instruments: Rudolph Research Analytical DDM 2911 Density Meter

Instrument Key Specifications

Density and Surface Tension of Ink

Inkjet printers can produce high quality pictures in a short amount of time. One important aspect to the print quality is the surface tension of the inks. Controlling the surface tension of the inks can help to improve their surface wetting properties to the printing media. One method to determine the surface tension of a liquid is the so-called Pendant Drop method. For surface tension measurements using the Pendant Drop method, a single droplet is suspended in air from a needle tip. The drop shape is then captured by a high speed camera for analysis. A fitting routine is used to analyze the captured image and determine the surface tension of the liquid.
The Pendant Drop method requires the density of the liquid to be known or measured. Other surface tension measurement techniques, such as the Wilhelmy Plate and du Noüy Ring, do not require the liquid density to be known. Nonetheless, the Pendant Drop method requires significantly less of a liquid sample for analysis. Just a few milliliters are sufficient for multiple surface tension measurements with the Pendant Drop method. In addition, the needle tip does not need to be cleaned using burning heat between measurements and is much more resilient to deformation than the Wilhelmy plate or the du Noüy Ring.

Two common printer ink colors are cyan and magenta. To determine the density, the cyan and magenta printer inks were measured with a DDM 2911 Density Meter manufactured by Rudolph Research Analytical (USA). Each ink was carefully injected into the Density Meter at room temperature. The results of the density tests for the cyan and magenta printer inks are shown in Table 1.

With the densities of both the cyan and magenta inks measured, the surface tension of each ink can be determined through the Pendant Drop method. The surface tension measurements were performed with a DM-701 Contact Angle Meter made by Kyowa Interface Science Co. Ltd. (Japan). The DM-701 allows for automatic liquid dispensing and drop size control. Figure 1 shows typical droplets formed by the cyan and magenta printer inks. The drop shapes were analyzed using the Young-Laplace theory.

The surface tension for each ink was approximately 30 mN/m with the cyan ink being slightly greater in value than the magenta ink. Both measured surface tension values fall within typical surface tension values for printer inks. Even though the Pendant Drop method requires more information about the liquid properties to be known than other methods, it still has advantages over other surface tension measurement techniques for certain applications where liquid amount is rather limited.