These are chemicals which lower the surface tension of the water and allow soiling to come free from the fabric. More importantly, they hold this soiling in suspension thereby preventing it redepositing onto the fabric.
Most modern detergents contain optical brightening agents or OBA’s. These are a type of dyestuff which attaches itself to the fabric during the laundering process. The action of OBA’s are to absorb light in the invisible ultra violet region of the spectrum, and re-emit it in the visible spectrum, principally as fluorescent white light. On white fabrics, the effect is to make the fabric appear “whiter than white”.
However, on fabrics dyed with small quantities of dyestuffs, namely pastel shades, the effect of the OBA’s can overpower the colour of the fabric giving a bleached or faded appearance, after only the initial washes. We therefore recommend that only detergents containing no OBA’s are used during the laundering process.