In addition to needing to clean the paint engine, we found too much residual energy in the vinyl paint delivery lines. Once the paint was pressurized it didn’t want to stop flowing due to gravity. So a measured pulse of paint would not stop at its desired volume… it would trickle additional paint into the color engine manifold. Thus, homemade pinch valves were fabricated to stop the flow of paint in the vinyl tubes… one for each color.