There is one other thing about mixing PO that you may want to know. I have mixed up batches a half dozen times in the last year and a half or so, and I noticed that I got a slightly cloudy solution when I changed chemical suppliers a while ago.

It appears that one of the component chemicals is not absolutely pure, and there is a slight brownish look to the solution. PO should look totally clear in solution.

I have used the PO without any problems for pt/pd printing, however the contamination could be an issue in another process. It is too fine to filter with a coffee filter, but a student grade filter will remove it.

I made a handful of filtering cylinders out of old plastic wide mouth bottles, by drilling holes in the lid, and cutting the bottom off the bottle. I screw the filter paper in the lid, invert in a tray and fill with the PO. It slowly dribbles through the paper and the residue that is left behind looks like an iron product.

Anyway, I don't think it is necessary to filter it, but you can if you want to start with clear PO. I suspect that if you started with reagent grade chemicals, there would not be a need for the filtering.