Coffee and Cream

An interesting technique when photographing water droplets is to try to get a 2nd droplet to hit the first droplet as it emerges from the water, this technique is called ‘water collisions’ or ‘double drops’. The technique is very dependant on accurate timing of the spacing between the two droplets and the moment the flash guns are fired.

The set up to create the water collisions is:

  1. A tank suspended from the ceiling containing the fluid being used.
  2. A tube from the tank goes to a direct acting solenoid valve clamped above the receiving tray.
  3. The solenoid valve is connected to a small computer which is used to programme the timing required.
  4. The nozzle below the solenoid valve is positioned directly over a small IR trigger beam.
  5. The IR trigger beam is connected to an electronic timing delay which fires the camera after a programmed delay and the flash guns are fired wirelessly from the camera.

Canon 40D with 100mm macro lens 1/250sec @ f16 iso 100. Two flash guns running at 1/64th of full power provide the illumination

7 Responses to Coffee and Cream

  1. Steve says:

    Beautiful images, and awe inspiring in an ‘inner space’ kinda way 🙂

    Thank-you for sharing.

  2. Bambi says:

    Hi Kev,
    been following your site for a while now and have decided to build myself an all in one controller box, which will fire off solenoids, flashes etc, based around an Adruino board, and the work of a very clever lady called Louise. Do you use something like an Opto Isolator in between your solenoid and your ‘small computer’?

    • photosbykev says:


      the arduino microprocessor is ideal for timing projects, I started using an arduino for my work and then went on to buy the purpose made modules. The solenoid is basically an electro magnet operating a plunger and does generate a significant back emf so you will need to put a blocking diode across the solenoid contacts to reduce this voltage which would damage the arduino. Using opto isolators is a good start but they may need to be protected. When I using the arduino I started using a simple solide state relay to trigger the solenoid, it had a fast response time for basic flash work.

      Don’t forget to protect the ardunio from the voltage spikes that some flashguns also produce, another place for an opto isolator

  3. Jack McGrane says:

    Hi Kev,
    I have been following your shots on Flickr and have ordered a Stop Shot unit to try my hand at it, I have made a mariotte syphon but can’t find a suitable nozzle – what do you use and what diameter is best – thanks for any help


    • photosbykev says:

      I use normal fish tank air pump tubing for my feed from the syphon and on the output of the solenoid valves I have a range of small pnuematic fittings typically from SMC, internal bores are anything between 2mm-5mm depending on the effect I want

  4. Ernie says:

    Awesome shots! I have done some drop photography with moderate success. I am in the next few days going to create a marriotte siphon and work on some collision shots. I would love to get a solenoid valve set up but I have no idea where I would find one. Can you help me with that?

    I have an IR trigger set up already, but to be able to control the drop timing would be outstanding!

    I look forward to your advice, as well as more of your great photos!


    • photosbykev says:

      I use a 24vDC valve from Connexion Developmetns in the UK, part number PU220AR. Alternatively you can buy a solenoid valve from Cognisys who make the Stopshot timing module.

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