Applications of Viscosity Control for Optical Lens Coating

For optical lens manufacturers, managing the coating thickness is crucial in the final stage of production of eye wear solutions such as sun glasses, safety glasses and other eye protection products. When coating optical products such as eye wear, it is important to maintain a uniform thickness throughout the manufacturing process.

Fluid viscosity is an important measurement when determining ultimate coating thickness, so it's important to monitor the fluid viscosity in-process to ensure that final coating characteristics meet the required specifications.

It is necessary to eliminate temperature fluctuations in the process, because even slight variances can impact viscosity, but not necessarily impact the solids-to-solvent ratio. Therefore it is required to implement an approach that negates the effects of temperature auctions in the process.


Determining temperature-compensated viscosity (TCV) is advantageous in the coating process. TCV defines the fluid viscosity at a reference temperature, which is different from the actual process temperature. It mathematically removes the viscosity variation caused by temperature to determine the viscosity change is being altered by the percentage of solids present.

PAC's 372 sensor is designed to be used in small-diameter process loops.

The true driver of the optical coating process is TCV. The real-time data from the VISCOpro enables customers to identify and solve issues before they impact product quality. Optical customers can confirm viscosity data with solids data in order to paint a picture of the molecular weight, without actually being required to measure the molecular weight.

The VISCOpro 2000 controls viscosity automatically, enabling customers to reduce scrap and enhance quality.

By maintaining the coating solids at the minimum levels needed to meet product quality specifications, the VISCOpro 2000 also helps to reduce operating costs.

Furthermore, it eliminates the requirement for destructive testing, and offers product traceability throughout the manufacturing process.

VISCOpro 2000 viscometers are designed to determine temperature-compensated viscosity to offer precise, in-line measurements. Before using a viscometer it is important to first define a temperature/viscosity profile for the coatings that accommodates the specific viscosity of the coatings used for each product type.


In conclusion, the results obtained with are VISCOpro 2000 are beneficial for several reasons:

  • It improves yield by reducing scrap
  • Reduces the number of solvents needed in the process
  • Enables operators to maintain control over the coating solids irrespective of temperature
  • Eliminates the requirement for expensive destructive testing procedures
  • The product is made traceable throughout the process

This information has been sourced, reviewed and adapted from materials provided by PAC L.P.

For more information on this source, please visit PAC L.P.


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