Glassware Tips for Reproducible Colour Measurement

How to care for your glassware

Our customers don’t have to remind us that our glassware cells for Spectrophotometers or Chroma Meters are expensive especially when they are used or cared for as consumables and we are constantly looking for more affordable options, but need to take into account the clarity and quality.

The price of glass cells is purely driven by clarity and quality, but do all applications require absolute consistency in terms of glassware colour and clarity. When are these required, and when can you use a cheap plastic substitute?

Plastic or Glass – Which cells are the right for your application?

If your procedure requires you to measure colour of objects in a glass cell or  glass cuvette, the clarity and colour consistency of that cell will have to match the tightness of the colour tolerance being measured.

For example, Tomato Sauce will be packed in fairly cheap bottles which will vary in clarity and “Yellowness” which while it will affect the colour perception of the measurement, the difference may be  within visual tolerances acceptable to the consumer. In this case the colour of the product is affected not only by the contents but also the colour of the plastic packaging, bottle or container.

In this case, some manufacturers opt for an opaque printed sleeve which even if in itself is not colour consistent, does not lead to a perception that the contents are inconsistent.

When it comes to requiring as close as possible to true colour with tight tolerances, say when measuring pigment concentrates or grading flour, then glass cells need to be as close to transparent as possible.

In this case, the material itself must be of the highest purity with consistent clarity. The less the effect the cell has on the colour of the measurement, the tighter the tolerances can be. The glass cells that we supply are of the highest clarity and optically neutral in colour. Each batch and each cell is also checked for colour to ensure optimal consistency and the highest quality.

A way to test this is to take a stable substance, even a calibration tile, and measure it repeatedly through variable glass types. In this manner you can measure the effect of the container itself. A large sample of measurements will result in a clear trend and deviation statistic which will either be acceptable or not.

Customers who want to further ensure repeatable measurement practices may implement a Black retaining ring to limit the amount of light that escapes through the sides of the cell and to avoid a phenomenon called ‘edge-loss’.

Cell Retaining Ring

Cell Retaining Ring

Some tips to prevent cell damage:

Naturally glass is fragile and should be looked after very carefully.

  • Keep clean – When cleaning use a recommended lab glassware detergent without OBAs and clean with water <40 degrees C.
  • Avoid scratching and chipping
  • Avoid staining permanently
  • Wash with gentle cleaning agents
  • Wash at low temperatures to avoid the laminating glue to fail (See Blog Image of a standard cell where the bottom has delaminated due to hot washing)
  • Keep an extra glass cell in stock

We have covered these tips in another blog: “Glassware Maintenance”