Pseudo gakked with hypromellose will form in cooling solvent from the STE, and when filtered out looks clean and white. It will not dry readily, seems to have an affinity for acetone, and as it dries, seems to turn into nothing but an oily spot on the filter. The white powder just seems to "melt" into the filter as it dries.
If your pseudo does this, dissolve it in alcohol and precipitate it in fresh xylene and naptha. Using the same solvents used to do the Straight to E to do essentially the same precipitation will yield much cleaner pseudo. As the solvent cools, gakk will precipitate in amounts that might surprise you. You will find the pseudo after this second preciptiation dries faster, reacts better, and doesn't melt into the filters.
You can see the same melting-into-the-filter phenomenon if you filter the white powder out of acetone used to rinse pseudo. If what you think is pseudo melts into a filter as it dries, you don't want to put it in the flask. It isn't pseudo, or it isn't clean enough pseudo.
That is what I referenced when I mentioned pseudo "melting" into the filter.