Here is another accidental discovery that I would like to share.
It was discovered by myself whilst carrying out conservation work and cornice repairs at Hamilton Square, Birkenhead. Cheshire. The Square was built beginning in 1826 to the design of Edinburgh architect James Gillespie Graham. It was second only to Trafalgar Square in London for having the most Grade I listed buildings in one place in England. (EDIT I got married in this square last year)

We were carrying out repair and reinstatement works within 2 adjoining properties facing the square that were being converted into luxury apartments by a local development company.  Most of the repairs were in situ patches to make good protrusions from the previous tenants (bank) as well as some historical damage. 
We worked our way room to room throughout the development making good each section using lime putty and plaster of Paris. It was a slow process as the rooms were tall and many of the cornices ornate.

A lot of time was spent climbing up and down mobile scaffolding towers using small mixes to make good the repairs. It was getting late and I didn’t fancy the walk down to the basement for water so I picked up a bottle of water that had been left in the room by decorators.

It happened to be a flavoured water. Volvic Touch of Fruit Lemon and Lime to be exact. I proceeded to make up a small mix with the water and was suprised to find that the set had been extended or retarded by the citric acid within the fruit drink.

In fact the effect was perhaps little too much. Extending the set to over an hour. We experimented with a reduced concentration of volvic mixed with fresh water and found we were able to fully control the set allowing us to work much more efficiently. We found that about 30-40% volvic added to our gauging water gave us plenty of working time and reduced waste material.

I hope that this tip can help somebody else in a similar situation although I do advise to make a test mix before you proceed.

Dave Lawton

http://www.specialistplastering.com