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Monday, June 29, 2015

What is bandpass and resolution when talking about spectrophotometers?

The smaller the bandpass the better the resolution. Current ISO 2469 conforming instruments are all 10 nm bandpass. However, the new Color Touch™ X will have 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.

Thursday, June 25, 2015

Technidyne Gets "Fresh" Calibration from NRC

Technidyne has just received its transfer standards (IR2) from NRC (National Research Council Canada).  The updated IR2 calibration will be used on the Master equipment and standards produced in July will include this fresh calibration.  

ISO Authorized Laboratories get fresh IR2 calibration from NRC on a regular basis. This is then used to produce the IR3 standards that everyday users calibrate their ISO 2469 conforming equipment. Calibration for optical properties in the Paper Industry includes calibration of spectral reflectance (minimally 400-700 nm), fluorescent (UV Level D65 & C) and non-fluorescent levels.  ISO employs a three level system of distribution of calibration standards as described in ISO 2469.  The three levels are:

IR1: The perfect reflecting diffuse (absolute reflectance)

IR2: Standardizing laboratories; National Research Council of Canada (NRC), NIST (USA) and PTB (Germany)

IR3: Authorized laboratories according to ISO 4094:

         USA        Technidyne Laboratory Services

         Canada    FPInnovations
         France     Centre Technique due Papier
         Sweden   Innventia

Standard Issue

ISO Standardizing

Establishes IR1 (perfect reflecting diffuse)
Evaluates IR2 against IR1

IR2 (level 2 standard)
ISO Authorized
Evaluates IR3 against IR2

IR3 (level 3 standard)
Calibrates test instrumentation with IR3

All of the ISO Authorized Laboratories exchange IR3's on a monthly basis to see how they agree and as a diagnostic tool to detect errors.  The labs also meet at least every 18 months to discuss procedures, discrepancies, concerns and coordinate projects.

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, June 22, 2015

Paper Barrier Properties: Cobb Test

Because paper is composed of a randomly felted layer of fiber, it's structure has a varying degree of porosity. Thus, the ability of fluids, both liquid and gaseous, to penetrate the structure of paper becomes a property that is both highly significant to the use of paper. The need to limit the spreading of ink resulted in "sizing" the paper with gelatinous vegetable materials which had the effect of sealing or filling the surface pores. Later, the term "sizing" was applied to the treatment of paper stock prior to the formation of the sheet, with water-repellent materials such as rosin or wax. Resistance towards the penetration of aqueous solution / water is measured by Sizing or Cobb values. 

The Cobb size test measures the amount of water a specified area of paper will absorb in a given length of time.  In this test, a circular metal ring is clamped on a weighed sample of paper backed by a rubber-covered metal plate.  A measured volume of test liquid is poured into the ring, allowed to stand for a preset time, and then quickly poured off.  The metal ring is removed, and the sample is blotted to remove all free liquid.  The wet sheet is then weighed.  The results are reported as the weight of liquid absorbed per are of paper surface, usually grams per 100 cm².  The test is very satisfactory for paperboard and for many types of paper.
  • Scott, William & Stanley Tosset, "Properties of Paper: An Introduction", p. 105-106, 1989.
  • TAPPI T 441 om-13, "Water absorptiveness of sized (non-bibulous) paper, paperboard, and corrugated fiberboard (Cobb test)"

Friday, June 12, 2015

Summer is Heating Up

Many times in business, summer is a time for vacations and slow down in terms of production and activity. At Technidyne, summer 2015 is ripe with activity.  Here are a few highlights...

Color Touch X is moving from Engineering to Production. The first shipments of the long awaited evolution of the Color Touch family of instruments will be going to customers.  Many Color Touch X instruments are already on order and demonstration instruments will be heading out for sales people to show to customers. Let us know if you want to see the best spectrophotometer in the world!

TEST/Plus is progressing with several devices (gloss and caliper) moving into pre-production. This is when we build 3-5 units to test drawings, kit lists and do R&R studies. These units will then move into production in late summer.  Also, new designs in the TEST/Plus line are moving along which will result in additional releases this fall.

The 2015 International Sales Meeting and Service Certification Training will be held in August at Technidyne Corporation in New Albany, Indiana, USA. Agents from around the world will get training on features, operation and service of new equipment from Technidyne.

E-commerce capabilities via our partnership with is expected to come on line this summer as well. Initially, customers will be able to order calibration standards and get recertifications started on-line. Eventually, additional parts and instruments will be available for order directly from the web.

Monday, June 8, 2015

Paper Barrier Properties: Hercules Size Test

The Hercules Size Test is an instrument flotation test that measures the decrease in reflectance of the side of paper opposite to that which has been covered with a given amount of ink.  The apparatus determines the time required for the reflectance of the sheet surface not in contact with the penetrant (ink) to drop to a predetermined percentage of its original reflectance.

Hercules size tests are more precise than ink flotation tests. Because of its high precision and objectivity, the Hercules size test is widely used as a routing quality control test.  However, the results are influenced by brightness, color, opacity, basis weight, and filler content.  The test should be limited to paper which range in grammage from 50 g/m² to 250 g/m². Procedures have been worked out for making grammage corrections to the test values when different weight papers are to be compared. Lightly-sized papers can give erroneous results if the liquid penetration time is very short.

Other tests designed to measure the sizing of paper include:
  TAPPI T 433, "Water Resistance of Sized Paper and Paperboard (Dry Indicator Method)"
  TAPPI T 441, "Water Absorptiveness of Sized Paper and Paperboard (Cobb Test)"
  TAPPI T 458, "Surface Wettability of Paper (Angle of Contact Method)"
  TAPPI T 491, "Water Immersion Test of Paperboard"
  TAPPI T 558, "Surface Wettability and Absorbency of Sheeted Materials Using an Automated Contact Angle Tester"
  TAPPI UM 481, "Ink Penetration of Paper" (no longer in print)
  TAPPI UM  596, "Water Absorbency of Nonbibulous Paperboard (Water Drop Test)" (no longer published, but available from TAPPI archives)

  • Scott, William & Stanley Tosset, "Properties of Paper: An Introduction", p. 105-106, 1989.
  • TAPPI T 530 om-12, "Size test for paper by ink resistance (Hercules-type method)"

Thursday, June 4, 2015

Technidyne at Paper Vietnam - June 10-12, 2015

Technidyne will be exhibiting at Paper Vietnam 2015 next week. The exhibition is for paper chemicals, machinery and products. it is being held at the Saigon Exhibition & Convention Center, Ho Chi Minh City, Vietnam.

Technidyne will be in booth # P12a exhibiting along side Certified Lab Consulting Company LLC (CLC) which is based in Thailand.  Products in areas of lab testing (Color Touch), automated testing (PROFILE/Plus™) and process control testing (FPAutoSpeck) will be showcased.

Paul Crawford, Asian Business Director, will be on hand to represent Technidyne personally.

Monday, June 1, 2015

What does roll hardness tell you? (Part 2)

Technidyne has experience selling and servicing the ACA Systems RoQ in North America. Here are some more illustrations of what the device can do.

Parent reel before and after calendaring

Paper roll testing
Customer rolls are cut from the same parent reel measured before the winder. 

Roll Side Measurement
Roll side measurement correlates well with the tension inside the roll.  Higher roll hardness relates to higher tension. 

For more information email Rodger Segelstrom or see the ACA RoQ website.