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General Print Supplies, Services for Printers
News Release from: Hydramotion | Subject: Viscolite
Edited by the Printingtalk Editorial
Team on 15 February 2006
Traditional Ink Viscosity Measurements
Unreliable
Techniques for measuring the viscosity of ink samples have been available for many years, said UK company Hydramotion.
Techniques for measuring the viscosity of ink samples have been available for many years, said UK company Hydramotion Despite their longevity and widespread use, however, many of them are awkward, time-consuming and unreliable, added the company
This article was originally published on Printingtalk on 16 Jul 2004 at 8.00am (UK)
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Instant Measurement Without Set-Up Or Calibration
The Viscolite 700 from Hydramotion is claimed to give instant spot measurement of viscosity without requiring any on-site set-up or calibration.
Viscometer Enables Press Operators to Go With Flow
With the Viscolite T15 portable viscometer, the latest addition to the range from Hydramotion, it is claimed that a press operator can easily measure the viscosity of a small sample of ink.
However, according to Hydramotion, portable viscometers, such as the company's Viscolite is now providing press operators with fast, reliable viscosity measurement that does away with the clumsy methods of the past.
Factory-calibrated to traceable international standards, the Viscolite needs no on-site calibration and is ready to use, said the company.
The claimed ease of use, convenience and accuracy of the Viscolite contrast sharply with the laboriousness and imprecision of other methods.
Further reading
Viscometer Ensures Inkjet Printing Performance
Viscosity and temperature are critically important in inkjet printing and A2N of Somerset, Wisconsin (USA) turned to the Hydramotion Viscolite portable viscometer for measuring ink viscosity.
Viscometer Helps Ricoh Save Time And Money
Hydramotion viscosity control is saving time and money and boosting productivity for Ricoh UK Products Limited (RPL) in Telford, Shropshire.
Viscosity Problems Removed For Tag Producer
The printing of identification tags with MEK solvent-based ink using a patented laser marking system has had viscosity problems cured by a Viscolite 700 portable viscometer from Hydramotion.
A traditional favourite in the printing industry has been the efflux cup' where viscosity is related to the time for a known volume of ink to drain out of an accurately-sized hole at the base of a specially-shaped container.
Although still widely used, that method can be seriously unreliable, especially at low viscosities, because of timing difficulties.
Moreover accurate temperature control, essential for reliable results, is often lacking, believes Hydramotion.
In its crudest form that method depends very much on the skill and experience of the operator, which can make repeatability hard to achieve.
Other traditional techniques include the falling rod method, where viscosity is related to the time required for a steel rod to fall a given distance through the ink.
Alternatively, using the glass tube capillary method, viscosity is related to the time for a given volume of ink to flow from a reservoir through a specially-shaped tube.
Both the falling ball and the glass tube techniques suffer from the same disadvantages as the efflux cup.
Additionally, such 'time of flight methods' have very low shear rates, so the values obtained often do not adequately predict what will happen on-press, said Hydramotion.
For example, if the viscosity falls at the higher shear rates typical of the press, the ink will tend to print weaker than would be expected from an efflux cup or falling rod measurement.
More recent techniques include the rotational and the 'tuning fork' methods.
In the first, viscosity is related to the angular velocity and torque when the ink is held between a rotating element and a stationary surface.
In the second, viscosity is related to the damping effect of the ink on a two-pronged vibrating element.
However, Hydramotion believes that both methods also have drawbacks.
The tuning fork method can only be used in large sample volumes, since it is prone to errors resulting from reflection of the sound waves from nearby surfaces.
Rotational viscometers present a number of problems.
Firstly, they must be calibrated and used in a vessel of known dimensions and they require regular recalibration.
In addition, they require a range of accessories, some of which are delicate and expensive, whilst the seals and bearings need periodic replacing.
As a result, the maintenance costs of rotational viscometers can be relatively high and a further consideration with those methods is the practical inconvenience of having to ensure that the equipment is properly cleaned after use.
The Viscolite is claimed to offer an escape from all the drawbacks of the other methods.
The smooth monolithic sensor can be wiped clean in a few seconds, and with no moving parts the Viscolite is virtually maintenance-free, said the company.
The Viscolite imparts shear stress to the ink by means of a stainless steel rod oscillating at its natural resonant frequency with a twisting movement.
The drag force on the sensor dampens the oscillation, and the resulting energy loss gives a measure of viscosity.
The shear rate is high, closely reflecting actual press conditions.
As no sound field is produced the Viscolite can be used in any container, regardless of size or dimensions, added the company. Request a free brochure from Hydramotion ...
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