Hi Martyn, you’re correct about building being just the beginning , it took me a few evenings to get a decent collision, (hence the late reply!) I have 3 different soleniod valves so I was getting bogged down and a bit frustrated, but I found that the length of the delivery nozzle on the solenoid can make a huge difference as the water left in the valve and nozzle can create problems with the second drop.
I got 4 nozzles and cut them to different lengths and after some experimentation I found one that suits. I also write down and keep my good collision results, (the height from the end of the nozzle to the surface of the fluid is worth recording as well) and I bought an ebook by Corrie White called The Ultimate Guide to Water Drop Photography (worth every penny)
Thanks to you and Corrie White, I’m getting some amazing results. Many thanks