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Question about freeze precipitation times

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Tasty Nuggetz

Rising Star
First of all, thanks to all of you who came here and wrote this wealth of information. It has definitely helped my friend in his endeavors.

Right now, my friend is running through his first extraction. Just for details sake, this is what he is doing:
Noman's STB tek
70g MHRB (powdered): 107g NaOH: 1600mL DIH2O: 100mL Naphtha (VM&P) per pull

He followed the procedure exactly as laid out in the tek with the exception of adding a little bit more naphtha than needed, because the measuring cup's lowest measurement was 100mL. He did 6 pulls from the solution, capped them, and set them in the freezer overnight (approximately 12 hours). When he saw it the next morning, only a few fluffy looking white crystals were on the bottom of only a couple of the containers. It by no means looked like the 0.5-1.0% that should have been there. Thinking that resulted from too much solvent, he set the open containers outside to evaporate (no fan) for about 6 hours. This brought down the volume some as well as putting already formed spice into solution with only slightly yellow sludge at the bottom (he is in the south, so it is really hot right now). After the evaporation, he capped them and put them back in the freezer.

Now he has read several different posts saying how long the crystallization should take, ranging from overnight to a couple of days. Is there any kind of consensus as to what should be the longest he should let them sit in there, before realizing it just will not have any more spice precipitate? He does have a really cold freezer, so please take that into consideration.
How many containers do you have your naptha in? Regardless, no matter how much surface area you're exposing through multiple jars, there's almost no way you've evaporated nearly enough naptha in 6 hours without a fan, given that you started with 600ml. Your total volume of naptha for freeze precip of 70g of mhrb should unquestionably be <100ml and probly closer to ~50ml or so. Once it's in your freezer you can either let it hang out in their for ~12 hours (cold enough to freeze ice cream hard) or you can cycle it back and forth from fridge to freezer every 4 hours for ~48-72 hrs.
Marsofold says to use 1 ml Naptha for every gram of MHRB, three times, and I found this to be sound advice. I usually get 85% of the spice on the first pull, 10% on the next, 5% on the last. The last can be a bit dirty.

But even better, is his advice to evaporate 90% of the Naptha (I think 75% is sufficient) or until it gets "cloudy." THIS is what you want to freeze-precipitate. When the spice is too dilute, it has trouble falling out of solution.

Your yellow sludge can be recystalized. The way I do this is to heat some water on the stove and then take it off when it is really hot but by no means boiling. Then I gently set a flask with around 50 ml Naptha into it. Once it is warm/hot, I use it to wash the sludge (and any utensils/plates with sticky powder on it from other crystals). This is collected in a temporary flask if there is color/gunk it it. I find that gunk does not like Naptha, and once it is all swirled, the gunk will sink to the bottom in bubbles. The Naptha can now be decanted off and the gunk will more than likely adhere to the surface walls of the flask. Add the now clean Naptha, containing spice, to a wide-bottomed scrapable container, cover in saran wrap, and freeze-precipitate.
Thanks for the help!

My friend had 6 containers overall. One for each pull. He evaporated them some more, and set them back in the freezer for ~13 hours. He did notice that the 3 last pulls had next to nothing in them, so doing 3 good quality pulls seems to be the magic number. That is a very important lesson for him, because that saves half of the time (and naphtha) for him.

He did notice that the container from the second pull had a lot of precipitate, but most of it was floating in solution (not on top). There was some stuck to the bottom, but not much. He thinks that is from having glassware with a pristine surface. In hindsight, he thinks it would have helped to scratch the bottom of the glassware a little bit to facilitate crystal growth. But then again, this is his first time and he could be wrong.

Now he is drying his crystals and will do a recrystallization as noted above from Lift (et al). From there he will see if a wash of Baking Soda (Sodium Bicarbonate) will be necessary or not. When everything is done he will provide an overall yield . . . . and a first experience into hyperspace.

On a side note, he did notice the same middle layer in his separation as found in another post:
He thinks next time, he will do a defat before beggining any extraction to eliminate this.
Lots of people cover their evaporation dishes (wide, casserole pyrex is best) with cloth to prevent fruit flies and bits of debris from falling in, but I've found that this, plus any yellow gunk, easily decants off. As clean as quality Naptha can be, when you are evaporating large quantities, you are inevitably dealing with petroleum distillate impurities.

Good Luck, I think you are on the right path now. Once you get a handle on just how many pulls you need to do by using separate containers, you can begin simply adding your subsequent pulls to your evaporation dish. But be sure to experiment first so you know if you are simply adding empty Naptha each time.
If you scratch the bottom of the jar you will encourage crystal growth. In SWIM's experience, scraping the bottom of an evap dish with a razor prior to evap/freeze precipitation causes mounds of smaller, finer crystals. Allowing the crystals to form over a longer period of time on a smooth-bottomed evaporation dish will create larger crystalline formations.

As far as that third layer, in SWIM's experience, whenever he has encountered it, it has been of such an insignificant volume he has not thought it worth the time or effort of an additional defat.
My friend informed me of some strange things that occured since the last post he wrote. So, he had the crystals drying in the containers from the freeze precipitaion, while at the same time drying the decanted naphtha in a evaporation dish. He left it for most of the day to dry (12 hours). When he came back, all the containers that had some crystals in the beggining, as well as the evaporation dish, had nothing but a yellow oily looking residue at the bottom.

He was very glad he kept everything in the container instead of filtering through coffee filters to say the least.

At this point, he is not too sure what to do. He thinks he remembers seeing a similar problem somewhere in the forum, so is going to research into it. He just wanted to keep everyone updated to his progress.

Edit: Since my friend lives in a really humid location, do you think this would have anything to do with seeing only a yellow oily residue?

He is going to recrystallize what he has, and see what happens.

Edit #2: Well, some research and trial later (about 2-3 hours), here is what happened. 25mL of Naphtha (VM&P) was heated in a water water bath until the naphtha was hot to the touch. This was then added to large a mason jar containing a noticable amount of the aforementioned "yellow oily residue". A rubber spatula was then used to agitate the residue into solution; however, most of the residue was insoluble in the naphtha and stayed at the bottom.

During this process, the naptha turned a bright yellow color. This was continued with all the containers with any noticle resiue.

Since this was a large volume of naphtha in total (about 100mL), this was evaporated with a fan. Within 5 minutes, it started turning the milky color described in other posts (as well as seen during the freeze precipitation earlier). Now, another freeze precipitation is being performed before an estimate of further cleanup is needed.

Edit #3: Well, after letting sit in the freezer for about 8 hours, the container was removed, decanted, and allowed to evaporate under fan an hour (still continuing). When the container was removed, my friend was quite surprised to see so much white stuff on the bottom; although it went immediately back to the yellow oily residue as soon as it warmed up to room temperature. My friend is almost baffled by all of this. For right now, the resiue is drying and will continue to dry for the next hour or so. He is not sure what is wrong. For the time being, he is going to hit the forum again and see if he can find something else while waiting for any changes.

The only thing he can think of is that he has a lot of impurities from having too much naphtha while extracting.
Well, actually, there is one more other thing. . . he thinks that living in a country that is really hot and really humid has something to do with it. The reason is this. Pulling out a really cold container in a hot/humid environment encourages thermophoretic deposition of the water onto his precipitate. In other words, the water condenses onto the surface of his precipitate from an extreme difference in temperature. As such, he is going to redissolve this again in a minimal amount of hot naphtha, then gently heat this in a water bath. Afterwhich he will evaporate all the solvent off. Sounds like the best way. . . .at least it worked last time.

Hopefully last edit: Well, the answer was found after reading through a good 340 posts of mainly repeated questions such as my friend's. He was correct that the humidity was the cause of all the troubles. He now knows to CAP THE CONTAINER AFTER YOU DECANT. From there, wait for the the wet crystals to approach room temperature. Then you can open the container to finish evaporating. He thinks doing this next time would make it easier and quicker. Lessons learned and lots of good stuff read. He says he will keep everyone updated with what happens.
Thanks for taking the time to read through his lab notes!!

ImPersonal Note:

First of all, you (guys/gals/non-gender specific entities) kick all sorts of good stuff. Even though it took a healthy amount of time, my friend was able to find invaluable information within your vault. My friend hopes that his experience is helpful to someone. . . . experience really is the best teacher.

My friend says it is so close he can almost taste it. This has been a LONG time in the maing (1-2 years), and he feels as ready as he possibly could be. Here's to hoping for a nice final stretch. . . . .:d
Well, here is what happened. After evaporation, all the white stuff was on the bottom with a clear yellow layer on top. This was then decanted and allowed to dry. After a few hours, there was a white oily product with remains of the yellow oily residue.

Starting to doubt skills, a test of mixed white and yellow oily residue was burned to make sure this was the right stuff. Oh Yeah. . . . this was the right stuff! Now all oily residue is in process of being dissolved in some more hot naphtha followed by a sodium carbonate of pH 8 solution wash. This will be decanted and allowed to evaporate until it turns milky. This will then be put in the refrigerator for a few hours moving next to the freezer until full precipitation is achieved. The crystals will then be decanted and immediately sealed until reaching room temperature. At that time, the container will be inverted to allow all solvent time to finish evaporating. Hopefully, there will be no oily residue this time. . .

Finally!!!! The answer to all of the precipitation questions asked and answered are found here:

That would have helped a couple of days ago. . .

Also just noticed that this was posted in the wrong thread. . .

The writer is feeling all sorts of fail right now. Not "reading" thoroughly before post fail and wrong thread fail. Let's hope it gets better from here.:oops:
For those who care, here is what resulted.

The above procedure worked and resulted in about a 0.7% yield. This is not at all surprising considering this was a first time. Now that everything seems to be working, a test of quality will be performed.
hello everyone. this will be my first post on the nexus.

SWIM just did his first 2 (VM&P) naphtha pulls from his 70g MHRB/80g lye/1100mL mixture and am wondering how much he should let evaporate before starting the freeze precip? And once he does put the naphtha in the freezer for 12hrs what should he do after? Should he leave it out for ~6hrs and then put back in the freezer or what? SWIM's first two attempts at STB extraction resulted in no yield. SWIM isnt sure what went wrong but he thinks it may be the pH and the freeze precip was done incorrectly. It seemed like he saw a layer of crystals in the evap dish but they disappeared, never to return?

Any help will be greatly appreciated. And btw i am glad to be a part of this forum. :)

edit:: another thing is that each one of SWIM's pulls was 100% clear, He was under the impression the naphtha would turn slightly yellowish?
You should let the naphtha evaporate until you see it look "milky" in appearance. Meaning you will not be able to see through the container when looking through it to the side. In other words, it will look "foggy" inside the container.

After freeze precipitation, do exactly as said above.

If you saw a thin layer of crystals when you pulled out your evap dish, then that means the good stuff is in there. They just went back into solution.

The only reason the naphtha would turn slightly yellow is if you are extracting out things other than the spice. The spice itself is a white crystal.

Nothing to be worried about anyway. Good luck!!
Someone once told me UV light is not good for evaporating, so dont do it outdoors. Keep your containers covered, even when evaporating. Small holes are efficient. Slow evaporation is a slow process, rushing the spice will not work. If you really dont feel like waiting, I freeze, get what I can through a quick scrape and strain, and then just reuse the naptha (pull n freeze) instead of evaporating.
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