After around 8 hours of sitting, the vinegar and naphtha separated almost entirely. Both layers were clear as water, with the vinegar layer being ever so slightly cloudier (almost imperceptibly so).
The evaporation test turned out to be very clean. There was no smell whatsoever of naphtha, and there was no tangible residue to scrape off. However, there was still a faint dry residue similar to the one witnessed by a previous user. It was clear and could not be seen unless held at an angle under light.
Obviously, washing the dish with water immediately removed the residue. It seems to me it may be an option to wash the "dried naphtha residue" off of DMT by a simple sodium carbonate wash. Although I understand this is used to remove only polar impurities, it seems to me like it is still washing nonetheless, and therefore must serve to clean it somewhat...
One thing I am curious about is why the vinegar took so long to clear, or more importantly, what this means for the integrity of the solvent (clear after about 5 minutes surely must be better than clear after 8 hours, but it is clear all the same).
If the impurities are nonpolar, neither a mini A/B nor a vinegar wash would remove it, if I have this correct. Re-x'ing with the same solvent would be next to useless for removing the residue of that solvent. Re-x'ing with a more selective solvent (hexane/heptane) seems to simply pass the problem over to the integrity of the new solvent. Not to mention it is unknown whether the new re-x would select against the residue of the previous solvent. Like dissolves like, and if the residue is nonpolar (which is the possibility we are trying to address here), hexane/heptane might very well pick it up as well.