Improving ink sustainability by using spectral data from leftover inks

Remixing leftover spot-colours from a flexo or gravure print run into recipes for new jobs is a big contributor to waste reduction in package printing. Efficiency and reassurance of repeatable accuracy is key – and that’s why the precision of a software-driven ink dispenser for dosing ingredients is vital.

In this blog we explain that introducing an additional integrated method of reusing leftovers, using spectral data, helps to improve ink sustainability while assuring full traceability.

The mathematical method: efficient for reusing most leftover inks

In the majority of cases, the fastest and most efficient way of reusing leftovers, or ‘press-return inks’, is by a ‘mathematical method’. This involves retrieving returns with a composition that’s compatible with the new spot colour you’re making.

As described in our previous blogs about this method, ink management software simply calculates and adds the exact weight of each fresh ingredient needed to make the target colour, while reusing press-return inks with a compatible composition.

It’s automated, fast, clean, and full ink traceability and costing is guaranteed.

When you can’t use the mathematical method for remixing leftover inks

But there are circumstances when it’s not desirable or possible to use this mathematical method of using similar compositions, for instance:

  • When you have a stock of return inks, with a wide variation of different ingredients.
  • When your ink mixture is contaminated, meaning that the formula, or proportions of base colours in it, is unknown.
  • When adjustments are made to a mixture at the press, without recording the type and quantity of new base colours added to the blend.
  • When you want to process a large stock of return inks on a one-off basis (e.g. when you change to a new ink series or ink supplier).

How spectral data helps you reuse problematic leftover inks

In these cases, you can use spectral data from leftover inks to create a recipe of a new target colour, using return inks and fresh inks to achieve the desired colour. By using a spectrophotometer and dedicated colour / ink formulation software, you can measure the leftover ink and add it to a library. During production, the software can generate formulations to run them off.

If this method is applied with stand-alone colour formulation software, the disadvantage is that you lose track of information about the ink container’s ingredients.

Thankfully, there is a semi-automated way of reusing inks with the spectral method, while also logging all ink logistic events.

The procedure requires the use of two software packages, and the ability of data to transfer between them:

  • Dedicated colour formulation software, to measure and store colour information about every press-return ink, by a spectrophotometer and create formulations of the target colour while reusing these press-returns.
  • GSE Ink manager with the optional GSE Colour connect and GSE Return formula dispensing software modules, to log the quantities of return inks, along with fresh ingredients to make the new colour.

The pros and cons of using the spectral data method

The big advantage of this new integrated method is that you have more potential to reuse leftover inks – without losing the logistical data for stock, traceability and cost management purposes.

But there are also a few disadvantages to this method:

  • Mixtures of reused inks will contain a larger variation of different pigments. This may result in less stable colours and reordering extra inks with the same composition at press may be impossible.
  • Unlike the mathematical method, you don’t always know beforehand how much fresh inks must be added to attain the target colour.
  • If you have used the spectral method, you cannot go back to the mathematical method for that container with press-returns.
  • It is labour-intensive.

The good news however is that you don’t have to choose: you can use both methods in parallel! You can apply the efficient mathematical method for processing the majority of the leftovers, while applying the spectral method for the more “difficult” press-return ink stocks to obtain an optimum level of ink sustainability.

In our next blog we will describe in detail how the “integrated spectral method” works.

If you need more advice on how to optimize the reuse of press-return inks, and for all ink logistics enquiries, contact us at