[skilled]

Spoon.

The larger surface area of the spoon compared to the tines of a fork means that when a spoon is used for stirring, it moves a greater volume of liquid with each motion. The broader stirring action helps not just in moving the particles around but also in ensuring that sugar is not concentrated in one part of the liquid.

You can also test it yourself with a transparent liquid (green tea), a fork will cause the sugar to be stirred in place at the bottom.

[giantg2]

This assumes you stir the same with the fork and spoon.

You can generally stir more quickly and chaotically with a fork. Stirring with a spoon will require a slower stir to avoid splashing over the cup edge. This ge really means that when you stir with a spoon you create a vortex concentrating the solute in the bottom center of the cup.

There's a reason bakers use whisks and not spoons for mixing - tines create more mixing actions.

[Jugurtha]

>This ge really means that when you stir with a spoon you create a vortex concentrating the solute in the bottom center of the cup.

This is considered improper with regards to "table manners". Many people do a circular motion with the spoon moving around the glass/cup wall. This creates a big stable vortex. The mass of the liquid is pushed against the wall and moves as a whole, similar to an annular flow, as you describe.

Another technique, the one I use (which appears to be "considered" proper, but our focus is on efficiency here), is a linear back and forth motion where the spoon moves forward and backward creating four unstable vortices every motion's period (T): two vortices on the left and right of the spoon when it moves forward (T/2), then two vortices on its left and right when it moves backwards (second half period, at date T, for a total of four vortices). These are quickly broken as they collide against one another every half period, and I suppose each particle's trajectory is more irregular with respect to a neighboring particle, which would mean a faster dissolution and a faster change in the concentration gradient.

That's how I've always thought about it. I'm not certain.

[garyiskidding]

thanks. Yes this is in line with my original thought too.

[garyiskidding]

Thank you .. will do this experiment.