So far I have tested:

- Three lighter fluid brands (Ronsonol isn't available in my country, but I guess it will result in the same) - All failed miserably with really dirty oily residue
- White Spirit - Failed miserably
- Technical grade Heptane - Left a watermark ring with a small oily residue in the middle
- ACS lab grade Merck-Millipore N-Heptane (<0.001% NVR) - Left a faint/thin oily watermark ring (a 150EUR bottle, I was really expecting a clean result here :/)
- IPA 99.9% - Left a faint oily watermark ring similar to the N-Heptane
- Ethanol - Left a messy watermark on the whole drop surface, not only the contour ring
- Acetone - Messy watermark ring with stuff in the middle. Probably had some water judging by how the drop expanded on the glass...

(the only thing that evaporated cleanly so far is a random 70% ethanol-water solution that I bought for hands sanitizing LOL, maybe due to the slow evaporation, who knows)

The tests were done on a glass plaque cleaned with dishsoap and rinsed with distilled water, I cleaned half of the plaque with IPA and tested on both sides in case the distilled water rinse wasnt enough.


I don't know if i'm doing something wrong or maybe it's soemthing in the environment? (Currently the humidity is very high (around 60-70%) and it is very hot here). I know that NVR testing is done in isolated cameras, sometime with some gas additions to avoid contamination from the air, and that could be the case here?

I've seen some mentions about a watermark ring being OK for the freeze precipitation process TEKs, so don't know if the ACS N-Heptane would be just fine to go, since it was the one with the less residue left behing.

Or should I order Ronsonol from overseas and try it? There's also a possibility of finding technical grade Merck Naphtha Benzine, but that one will be as expensive as the N-Heptane and the NVR in the specification is 5x higher than the N-Heptane one...

Perhaps you should describe your steps from beginning to end instead. Which extraction method are you using? It might not be the issue with solvent. Since you had wrote euro, there were successes using something like wasch-benzin (in Deutsche and variations of it should work too).

High humidity and high temperature will certain produce more resulting in gooo, which can go into making changa as a way to make it more manageable. Good luck

I want to go with Cyb's Salt/Max-Ion tek, which does include a freeze precipitate step.
The evaporation result is only for the solvent test, I havent started the extraction process yet!

Wasch-Benzine isn't available here sadly :/, I can only get the mentioned naphtha benzine, which would be high technical grade, and expensive...

Sorry to hear you are having difficulties. I’m in Duhmerica so can’t speak to what’s available to you. I know that most of us kitchen extractors here use Varnish Makes and Painters (VM&P) naphtha, which is anything but lab grade. It really seems to me that your lab grade heptane should not have contaminants. Do you have the MSDS for the products you are using?

Hopefully someone with better knowledge of…everything… including the specifics of what’s available to you will chime in.

I can feel your frustration, nothing like that so close but so far feeling. Good on you for being cautious though, it shows integrity and patience, two great qualities for an explorer.

Sure, this is the documentation on the N-Heptane, which is the most "serious" one :
https://anonym.es/?https...-Heptane,MDA_CHEM-104379

The lighter fluids were only "light petroleum distillates", or very simple sheets with no other data in their MSD's, and the Technical Heptane just says 99+% Heptane, and no more meaningful stuff (but since Heptane is a mix of isomers, some are probably non-volatile)

VM&P Naphta isn't available either, but I've seen several bad evap tests on it around, so I never got interested in that one.

Evaporating IPA and ethanol should always have no residue.

Could you try evaporating on a different plate and seeing if it happens there?

Ok.

I tried in two other glass surfaces with the same result for IPA, it leaves a faint oily watermark ring around the perimeter of the drop. :/

It is possible that during the evaporation process some surrounding water molecules condensate in the border of the solvent and air creating whatever makes that ring? Coupled with the hot temperature and the cold glass surface?

Edit: From some online IPA 99% specification sheets, they always have a 0.002-0.005% NVR, which is similar to the Heptane one, maybe that faint ring are normal within those NVR ranges?

Thanks. Would it be possible for you to take a picture of the ring and upload it here?

My cellphone can't focus on it Been trying 20 min with different light sources with no results.

I also tried the N-Heptane again to send a comparison with the IPA, but the drop didn't left any residue now lol, I repeated the process twice and only managed to get a small and barely noticeable watermark in the center of where the drop was before, of approximately 1/30 the size of the drop (similar to whats left of a raindrop on a window).

Edit: Ok managed to get the IPA one, the one from Heptane was impossible to get, its like 3 times fainter than that.

I'm quite sure your ACS grade heptane will be fine. That IPA looks ok too as long as you're not evapping large amounts of it, but I've never extracted with IPA so I can't really speak to that.

For what it's worth, I buy technical-grade heptane and acetone and do a fractional distillation on them myself to clean them up. Even my carefully distilled solvents leave a faint watermark on a glass mirror. The ring is always about the same regardless of how much solvent I evaporate, so I've come to suspect it's due to invisible residues stuck to the glass rather than impurities in the solvent.