The Binding Solution includes NaI, HCl, Triton-X100, and water. We have had lots of trouble with it, largely due to a mistake that has been corrected. In our hands currently, the Binding Solution is a pale yellow\u2014a possibility mentioned in the Rabe Cepko paper. It does seem to become cloudy over time (days to weeks). Our current plan is to prepare weighed-out NaI and the other components premixed (stored at 4C) for easier prep, and then make fresh Binding Solution up at least weekly.We have moved to storing the Binding Solution in 5mL amber screw cap tubes for development runs (2.25mL for a single strip of 8 samples), with these in an opaque container. This makes it convenient to add glass milk and use it as a master mix (as suggested by Rabe Cepko). Care must be taken to keep the silica resuspended prior to pipetting for the addition to the sample, hence the mixing by pipetting on every draw.