An evap test on a glass dish leaves a hard to spot oily residue on the dish. SWIM has not used Naphtha but instead washbenzin. Here's what it says for ingredients on the back:

> 30% aliphatic hydrocarbons, C6-C7, N-ALKANES, ISOALKANES, CYCLENES < 5% N-HEXANE
The technical sheet says the boiling range is 80°C-110°C

SWIM is unsure whether this can be used for extraction (STB, crystallization, no evaporation). The substance can be used as a cleaning solvent as well as lighter fluid, which might mean that inhaling its fumes in low amounts is not hazardous?

SWIM put a lighter to a small amount of the residue to see whether it would light on fire and it did not.

The exact product is "Spezial-/Waschbenzin" from "Bauhaus"

Would an extraction be safe? Naphatha is hard to get for SWIM.

If you can't obtain clean naphtha then use another solvent or method. Toulene is fine, so is xylene (pulls more). You could even do a dry-tek with sodium carb and use acetone to pull spice.

Necessity is the mother of invention. Get busy with being creative.

Pretty messy stuff.

I would recommend to learn distillation. This is an easy and relatively safe tek, described extensively on the internet. It will solve the problem of dirty solvents for you once and for all. Also you will be able to recover most of your solvents after extractions and re-use them. However, you will have to invest around $50 in glassware and some time to learn the tek.