Substitution of amaranth as dye in edge wicking test
Stora Enso, a big Swedish-Finnish forest industry company, wants to find a substitute for the dye that is used in their edge wick analyzes. The dye amaranth, that is used today, is a classified substance that is unhealthy and hazardous. It causes irritation to the eyes, skin and respiratory system. Edge wick is a method to determine the amount of penetrated liquid into the unprotected edges of a packaging board (the surfaces are covered with plastic). It is important to analyze liquid penetration to know that the board will sustain the liquids that it might be exposed to, for example sterilizing liquid (hydrogen peroxide), juice or wine. The dye is used as coloring agent for colorless solutions to enable visual evaluation of the penetration. In the present study several colorants were screened and evaluated in edge wick tests with the standard test liquids used at Stora Enso. Machine, pilot and handmade boards were used in the tests. Surface tension of some test liquids was also determined, as it is important to know if the dyes change the liquid properties since this may influence the penetration. The result of the tests was that a new dye was found, Allura red AC. It has a similar chemical structure to amaranth and seems to act in the same way in different type of test conditions. The recommendation is that amaranth be substituted for allura red AC, since the latter is less hazardous and is not a classified substance.
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