Mortar Plasticiser

Dunno about all that but I thought it was used for protection against water seepage?

Just to point out that quite a number of cements do actually have such additives already, well, added. E.g. some/all Mastercrete. Think there might be something in the FAQs about it.

Basically does the same as washing up liquid i.e. reduces the amount of water you need, which in theory results in a stronger end product. Cement plasticisers are normally lignosulphonates I believe. Very small molecules but doesn't foam significantly

The yellow plastic bagged version has it, the paper bagged one does not IIUC. (the topic seems to acquire "holy war" status between advocates of each type!

well, I am not an expert either on this, but for what is is worth:

Suggesting it should flow better I expect - makes it easier to tap a brick into final position perhaps (or by the same mechanism, slump too much that you need to redo it!)

What a builder would describe as "more fatty", slides off the trowel better etc. How does it work - I would guess by altering the surface tension of the water - making it wet surfaces better.

Drier mixes shrink less on curing, and "Enough" water tends to get a slightly stronger mix than too much. With the plasticiser you can get a drier mix to behave in a way that you want.

IME, yes (assuming you are using a cement that does not already have it). The "traditional" (but far from ideal) standin is a squirt of washing up liquid. (it weakens the mix among other things)

As with all surfactants, an excess is counter productive and a "squirt" is probably enough to do a 50kg mix. Because there's no emulsifying to be done, it's basically the wrong thing to use anyway.

Yes it works, the most noticable thing is stop the water seperating from the mix, IE, if you mix just sand and cement with water, put it into a bucket and carry it about for a minute, you'll notice that the water has puddled on the surface, and by the same token, the bottom half of the mortar is now almost bone dry, similar to when you tap your feet on a wet beach and the seawater pools up, with plasticiser this doesn't happen - it keeps the water in situ within the mortar, and also less water is needed, resulting in a stronger mix and a quicker drying one

So make Morecambe Bay safe - pour a few gallons of mortar plasticiser over it, allow tides to mix well. :-)