How to turn oil into in a gel?
Put your asphaltene source on a silica gel column and elute with hexane and then hexane/toluene mixture to remove paraffins (saturated compounds), aromatics, and resins (small polar compounds). At last, remove the asphaltenes (high molecular weight polar compounds) with pure toluene, evaporate to dryness (a brittle black solid), then with heat you can disolve/disperse the asphaltenes in a simple high molecular weight neutral material like petroleum jelly and let it cool. This will give a high and/or adjustable concentration of what you want to look at. https://en.wikipedia.org/wiki/Asphaltene