Does FAS remove ink, ash, stickies or contaminants?
Direct Answer
Direct Answer These have to be taken separately. formamidinesulfinic acid (FAS) is a reductive bleaching agent, not a general-purpose cleaner.
How FAS relates to each target
| Target | Does FAS help | Comment |
|---|---|---|
| Ink | Partly | Acts on the coloured components of the ink to help decolourise; does not replace flotation and washing as physical removal |
| Ash | Essentially no | Ash is mainly inorganic filler and coating pigment, removed by washing, flotation and dispersion |
| Stickies | Essentially no | Hot-melt and pressure-sensitive adhesives need dedicated dispersion, adsorption or screening |
| Colour | Yes | Chromophores are reduced and colour falls; this is the core function of FAS |
Where it belongs
FAS belongs in the decolourisation and brightness-lifting step, not the contaminant-removal step. The cleaning power of a deinking system comes from flotation, washing, screening and the chemical package, and FAS only improves the colour part of that.
Working with deinking chemicals
Where the targets include both brightness and dirt count, the usual division of labour is: the deinking agent detaches ink from the fibre, flotation or washing carries it away, and FAS pulls down the residual colour. Each has a distinct job and none substitutes for the others.
Bottom line
FAS is about colour. It has a partial decolourising effect on ink and essentially none on ash or stickies, which need their own removal processes.
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