I don't think anyone ever has come up with the definitive answer as to why today's detergents cause foaming into the rinse. No doubt there is some residue that isn't being rinsed away, but then again fibres are absorbent and difficult to rinse totally clear of detergent. Indeed, I think the accepted wisdom is that rinsing is simply a process of dilution rather than total removal - fabrics just have to the wash water diluted to such an extent that any residue poses no problem.

I recall reading once that nonionic surfactants used in detergents are extremely difficult to rinse away but that shouldn't necessarily pose a problem.

Soap, as has been discussed many a time on here, is actually very difficult to rinse from fabrics. Your rinse water might look crystal clear but that's not to say there wouldn't be significant residue in the finished laundry.

As to stiff clothes, is it only when you use the gel that it's a problem? Would a powder product for colours work better? You might think a liquid would leave clothes softer but sometimes it isn't the case: I remember years ago that Ariel Futur powder for colours left clothes softer than the Ariel liquid for colours, for example.

Seems you need to keep buying small packages of the various products til you find one you can put up with. The own-brand products - often by McBride - seem to be less susdy on the whole if that's any help. But yearning for crytal clear, bubble-free rinse water might - for the moment anyway - be a rather fruitless experience!

Maybe I shouldn't admit it but your rinses look much like mine do (and have done for most of the past 15 years). Unfortunately I can't find a final rinse shot in my files.

I can't say I have much problem with clothes being stiff from what I'd term as detergent build-up, except perhaps with Ariel bio which left towels a bit on the harsh side (the tablets were better than the powder). Too much static drying is the main culprit for stiff laundry in my experience.

The slimy/sticky feel certainly used to be a problem with Ariel liquid of 10-12 years ago but not so the last time I used it; I've never used the Excel gel to find out what it's like, having been wary of the overpowering perfume element that might have been tweaked for the better of late.

...that was just put out in the interim before they launched the gel, probably so they could have something equivalent to Small and Mighty on the shelves. A shame really - it was quite nice stuff and had the more subtle perfume the ordinary liquid used to have in the early 2000s.