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Monday, August 22, 2016

ISO OPAL Group - What is it?

I will be Stockholm, Sweden this week for OPAL (Optical Properties Authorized Laboratory) meetings.  The OPAL is made up of representatives of each of the Authorized Laboratories for producing and distributing IR3 standards for optical measurements according to ISO 2469 for the measurement of ISO 2470, 5631, 11475, 11476, and 22754 (and others).  This group is led by the Chairman of ISO TC6/WG3 (optical properties).  Representatives are from:
  • Technidyne Corporation - USA
  • Innventia - Sweden
  • CTP - France
  • FPInnovations - Canada
In order to maintain a high level of agreement among the labs, they participate in monthly inter-laboratory comparisons. This means the labs produce and ship standards to each of the other labs each month. They read the standards that were received and generate a series of tables showing the monthly comparisons of spectral reflectance (minimally 400-700 nm), fluorescent (UV Level D65 & C) and non-fluorescent levels.. This data is then maintained on a common website for later analysis.  This aids the labs in detecting differences or changes among the group.

In regularly scheduled meetings (like the one in Stockholm), each lab reports and discusses any observed trends, changes or differences. This helps build a cohesive group for issuing standards. The idea is to provide the best agreement among customers that receive standards from any of the Authorized Labs. A new report will be issued by the OPAL in the near future which illustrates the inter-laboratory reproducibility.

To learn more about Technidyne's calibration process and materials, contact Nick Riggs and see our website Technidyne Laboratory Services

Technidyne...for good measure. Visit us at

Monday, August 15, 2016

What is TSI Area and how is it used?

Most are familiar with the "peanut" ellipse the is produced from ultrasonic fiber orientation measurement devices. It is a numerical approximation used to transform the data into a polar diagram.  The area of this polar angle plot is the TSIArea .

With a well adjusted head box, the TSIArea is used to measure the influence of a change in jet-wire speed difference or pressure changes in the head box.

When comparing TSIArea in one running condition to another, a fiber quality index can be used to more easily explain the reason for the change.  Ideally, the operator of the device will enter the TSIArea(target) value based on statistically relevant measurements and the goals of the operation. When the sample is measured, both the TSIArea(measured) and the "fiber quality index" (ratio shown below) are displayed.

____________________________________       = fiber quality index   [no units, expressed as a decimal]


Technidyne has been selling fiber orientation measurement devices and helping people with their use of this technology for over 20 years. If you have experience using TSIArea, please share it here.

Friday, August 12, 2016

New PROFILE/Plus System Shipped to Vietnam

A 10-module, PROFILE/Plus™ test system was shipped to Vina Kraft in Vietnam last week. Today, all team members enjoyed a lunch consisting of Chinese favorites to celebrate (there aren't any Vietnamese restaurants in our area). There were a lot of people involved in the process from securing the order to building and testing instruments and setting up profiles and shipping the equipment. The system will be installed next week.

Vina Kraft, Ho Chi Minh City, Vietnam is part of SCG. SCG purchased a PROFILE/Plus™ system for their Chiangmai, Thailand facility nearly 10 years ago. They purchased additional PROFILE/Plus™ modules and Color Touch™ instruments in 2010.  The automated PROFILE/Plus™ test system includes: tensile, caliper, burst, grammage, roughness, porosity, brightness, color, formation and fiber orientation. The system will be measuring linerboard with a grammage range of approximately 100 to 250 g/m2

More on SCG:
4 awards from Thailand Corporate Excellence Awards 2015, including Human Resource Management Excellence which has been awarded for 14 consecutive years, Innovation Excellence which has been awarded for 10 consecutive years, Product/Service Excellence for 6 consecutive years and Leadership Excellence for 3 consecutive years. Thailand Corporate Excellence Awards is organized by Thailand Management Association (TMA) and the Sasin Graduate Institute of Business Administration of Chulalongkorn University. Nominees are selected by CEOs of 1,000 top companies in Thailand.

SCG has been selected by the DJSI (Dow Jones Sustainability Indices) to be world's Industry Leader in Construction Materials for the fifth consecutive year. SCG has retained this prestigious recognition from 2011 and had been on the Gold List for eight years running from 2008 – 2015. Dow Jones Sustainability Indices (DJSI) is a security index that assesses and benchmarks sustainability performance of the world's leading companies and mutual funds from around the world. Those listed in the DJSI are screened for their ability to generate sustainable returns to investors.

SCG has been Awarded "SET Sustainability Awards 2015", "SET Social Enterprise Investment Awards" and "Thailand Sustainability Investment Awards" from The Stock Exchange of Thailand (SET) 

Monday, August 8, 2016

The Physics of Fluorescence

What is really happening when something fluoresces? Electromagnetic radiation at one wavelength is absorbed and is then re-emitted at a longer wavelength.  Wavelengths of light correspond to perceived colors (if they fall in the visible range), and this means that shorter wavelength light like ultraviolet or blue is converted to longer wavelength light, like blue, green, yellow, orange or red.

What really happens:

  • Photon #1 hits a molecule
  • Photon #1 absorbed, electron at ground level gains energy and jumps to higher level
  • Electron loses some of that energy
  • Electron jumps back down to ground level and emits photon #2
  • Photon #2 has less energy, corresponding to a different color (longer wavelength of light)
           Jablonski Diagram for Fluorescence
A Jablonski diagram (right) is typically used to illustrate the physics of fluorescence. In the diagram electronic (energy) states are indicated by bold horizontal lines. The thin horizontal lines above them represent vibrational/ rotational sublevels. Electrons are normally at the lowest energy state, indicated by S0. When a photon (indicated by the blue line entering from the left) with appropriate energy interacts with a molecule the photon may be absorbed, causing an electron to jump to one of the levels of an excited state (S1 or S2 in the diagram). By ‘appropriate energy’ we mean an amount corresponding to the energy difference between the ground and excited states. Thus not all incident photons are equally likely to be absorbed. This transition process is very fast, on the order of 10-15 seconds (a millionth of a billionth of a second).

An excited-state electron rapidly (on the order of 10-12 seconds) loses its energy to vibration (heat), a process called internal conversion, and falls to the lowest level of the first (S1) excited state. From there the electron may fall to one of the sub-levels of the ground (S0) state, emitting a photon with energy equivalent to the energy difference of the transition. This happens on a time scale of nanoseconds (10-9 – 10-8 seconds) after the initial photon was absorbed. Since the emitted photon has less energy than the absorbed photon it is at a longer wavelength. This explains the magical process of fluorescence that converts light of one wavelength (color) to another, and leads to the phenomenal display of highly saturated colors in corals and so many other marine organisms.

The probability that a photon will be absorbed varies with wavelength (energy). Even for those photons that are absorbed there are other processes that compete with fluorescence for de-excitation of the excited-state electrons. The number of photons fluoresced relative to the number absorbed is the quantum efficiency. The higher the absorption and quantum efficiency, the brighter the fluorescence.

Principle of Fluorescence1. Energy is absorbed by the atom which becomes excited.
2. The electron jumps to a higher energy level.
3. Soon, the electron drops back to the ground state, emitting a photon (or a packet of light) - the atom is fluorescing.

Another way to think about this is with the old model of electrons orbiting around the nucleus. In the ground (S0) state the electrons are in the orbital closest to the nucleus. When they absorb the energy of an incoming photon they jump to a higher orbital (S1, S2, etc.) or its sublevels. They can’t jump to the spaces between orbitals, and that is why not all wavelengths of light will make something fluoresce.  The best way to document the fluorescence properties of a particular specimen is to measure excitation and emission spectra.

Wednesday, August 3, 2016

Spectrophotometers: Bandpass & Resolution

The smaller the bandpass the better the resolution. Current ISO 2469 conforming instruments are all 10 nm bandpass. However, the new Color Touch™ X has 10 nm, 5 nm and 2 nm bandpass capability.

Excerpt from: 
  • Workman Jr., Jerry & Art Springsteen, "Applied Spectroscopy: A Compact Reference for Practitioners", p. 19-21, 1997.
The terms bandpass and resolution are used to express the capability of a spectrometer to separate spectral bands or lines that are separated by some finite distance.  For an instrument that disperses energy over a prespecified spectral region of the electromagnetic spectrum, the bandpass of a spectrometer is used to describe which portion of the spectrum can actually be isolated by the spectrometer in a "pure" wavelength form.  The spectrometer bandpass is dependent on the dispersion of the grating and the entrance and exit slit width.  An example is often used to illustrate the problem associated with  measuring monochromatic light using conventional spectrometers.  If the ideal spectrometer was used to measure a bright line emission spectrum at a single wavelength (Fig. 8) the spectrum would appear as a single line.  What really occurs when such a spectrum is measured using a conventional spectrometer is a broadband spectrum as shown in Fig 9.  The spectrum assumes a Gaussian-like (or bell-shaped) curve.  This characteristic
broadening of a line spectrum through the spectrometer is an illustration of the spectrometer bandpass.  The actual bandpass for any instrument is assigned a value by determining the FWHM height of the bell-shaped spectrum.  Thus, for the band in Fig. 9, the FWHM could be empirically determined by finding the wavelength at which maximum intensity occurs and measuring the peak height at this position.  This height measurement is divided in half and the bandwidth is measured at this half-height on the band as illustrated in Fig. 10.

To summarize, bandpass and resolution are identical in practice.  Only for the resolution specification of a spectrometer is the expression of bandpass under the specified measuring conditions of an instrument dependent on the slit width settings.

Monday, July 18, 2016

Legacy of TAPPI Opacity

The last BNL-3 to ever be sold was shipped from Technidyne Corporation (New Albany, Indiana, USA) last week.  Nearly 700 BNL-3 (and previous model BNL-2) TAPPI Opacity instruments have been manufactured and sold since 1978.

Developed in the 1930's, Bausch & Lomb was the original manufacturer of the TAPPI Opacity instrument. TAPPI T 425 was written around this instrument which was developed to measure of the hiding power of a material. In most applications, it is a sheet of paper or a single layer of flexible packaging.  The initial idea was to compare the reflectance of a single sheet backed with a black body to the reflectance of a single sheet backed with a white backing with the highest known reflectance.
Bausch & Lomb Opacimeter (gen. 2)

Magnesium oxide was the highest reflectance across the visible spectrum at the time of the development of brightness and opacity. Therefore, the reflectance of magnesium oxide was set as the 100% point on the brightness scale in the 1930's.  Likewise, magnesium oxide was going to be used as the white backing for the measurement of opacity.  The problem was that magnesium oxide was very unstable (it yellowed quickly when exposed to air) and it was a chalky material which would be affected when coming into intimate contact with paper.  The solution was to place a piece of glass between the magnesium oxide and the paper.  Magnesium oxide was replace with magnesium carbonate which was more stable. These two changes led to a white body with a reflectance that was 89% of the reflectance of magnesium oxide.
BNL-2 Opacimeter (2 piece design)

Bausch & Lomb sold the rights to the opacimeter to Diano Corporation (Woburn, MA, USA) around 1970. Diano also purchased the rights to the GE Brightness design originated by Kimberly-Clark and General Electric (the basis for TAPPI T 452) from Martin Sweets Company (Louisville, KY, USA).

Jerry Popson was an employee of both Martin Sweets and Diano. He was involved in design and sales of the equipment. He started Technidyne Corporation in 1974 with the opacimeter and brightness tester.  The BNL-2 Opacimeter™ was manufactured by Technidyne from 1978 to 1987. The BNL-3 Opacimeter™ was manufactured by Technidyne from 1987 to 2016.
TEST/Plus™ Opacity from Technidyne
A new generation of laboratory testing, TEST/Plus™, has an opacity testing instrument. TEST/Plus™ Opacity by Technidyne Corporation includes the key elements of the design of the original opacity instrument along with modern electronics and user interface. The TEST/Plus™ Opacity instrument is current available.

Tuesday, July 12, 2016

Tensile Testing Basics

Tensile breaking strength has always been considered the most fundamental strength test run in the Paper Industry. It is more complicated than it appears since it involves tensile, shear and flexural forces acting on the fibers and bonds in the sheet.

In a tensile measurement, a paper specimen of uniform width and length is clamped between two jaws.  The jaws are then separated to exert a tensile stress on the specimen, and the instrument indicates the tensile force when the specimen ruptures. Most modern instruments also indicate the stretch and tensile energy absorption (TEA). TEA is the area under the stress-strain curve. It is proportional to the energy that the paper can absorb up to the breaking point.

In the Paper Industry, vertical and horizontal tensile testers are most common. However, there is the pendulum-type tester as well. Sample width and length are important variables in the tensile test. Longer specimens give a greater chance for weak points to exist, provide initiation points for rupture, and result in lower tensile strengths. TAPPI Test Method T 494 specifies that the test specimen be 25 +/- 1 mm wide and long enough to be clamped in the jaws when they are 180 mm apart. Also, the specimen must have sides parallel within 0.1 mm. 

Tensile breaking strengths are reported as the force per unit width required to rupture the specimen. This is often reported as lb/in or kN/m. Tensile breaking strength corrected for grammage is called the tensile index. A similar quantity called the breaking length is also used for reporting grammage corrected tensile strength. Breaking length is defined as the length of a strip of given paper that will cause it to break under its own weight. It is calculated by dividing the tensile breaking strength by the grammage. Tensile strength can vary dramatically from machine direction to cross machine direction.

Tensile Specimen Cutter
Tensile strength is a direct indication of the durability and potential end use performance of a number of papers that receive direct tensile stresses in use, such as wrapping, bag, gummed tape, cable wrapping, twisting papers, and printing papers. In general, a certain minimum tensile strength is required of any paper that undergoes a web converting operation where it is subjected to tensile stresses during startup and while being pulled through the process. Printing papers are a primary example of this.

There are several ways to increase the tensile strength of paper. For example, increasing beating or refining, increasing wet pressing, adding a beater adhesive, increasing long fiber content of the furnish, and increasing the basis weight will all usually lead to improved tensile strength.

Do you see any change in the use of tensile tests and measurements?

Are there applications where a pendulum-type tester is preferred over a vertical or horizontal tensile tester? Why?

Is there a good way to estimate tensile with other tests?

Common Standards:
ISO 1924-2 Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method (20 mm/min) 
ISO 1924-3 Paper and board - Determination of tensile properties - Part 3: Constant rate of elongation method (100 mm/min) 

TAPPI T494 Tensile properties of paper and paperboard (using constant rate of elongation apparatus) 

NOTE: Tissue and wet tensile are discussed under a different blog post.

Reference: "Properties of Paper: An Introduction" - Scott, W.E & Trosset, S. p. 56-58 (1989)