The Machine that Goes DING! When is a slab done?

I get so many inquiries about precise processing times for shatter and waxes in a vac oven. Most people just want to know when it is finished and purged of all residual solvents. We did some work with an RGA sniffing the vapor stream and we found that it was not a 1:1 relationship between solvent in the vapor and solvent in the slab. It just wasn’t a viable detection technique and couldn’t drive the process like we hoped it would.

SO, smarty pantses, how does a girl know when the slab is purged of all residual solvents? How do you time your purge cycles? How can we accommodate for batch variations and get this locked down and automated?

I appreciate your feedback in advance!

That’s a pity. Sounds like a decent strategy.
Doing some math based on slab temp might help a little.

My favourite method was based on candy making, and I aimed for “hard ball”

Take 500mg sample.
Roll it into a ball between your fingers.
Put it on lab bench and ignore it for 15min.

Rate it as you would hard candy.
When you reach “hard ball”, you’ve got what the boss was looking for…

either way, you’ve got a 500mg dab coming your way :wink:


I know all about candy making! Sounds like a win-win method

So how bad was the correlation?

Which confounders did you try and eliminate? I see temp, strain, batch size, and operator.

with “operator” covering all sorts of sins. eg variations in starting solvent ratio & vac-down speed, and what their flipping routine is. :stuck_out_tongue:

How where you sampling? How expensive would it for me to gather data?

I’ve rarely had to go up against residual solvent testing in any real manner, because almost everything I did that required testing had been winterized…and the geniuses in charge of the rules in Oregon removed Ethanol from the solvent list.

For the short period where I had to beat 5000ppm EtOH, “hard ball” kept both the boss and the state happy. “soft ball” was border-line, and could land on either side of 5000ppm.

Once I spin hydrocarbons back up in our new space, I’ll be making unwinterized live resins and almost certainly playing with Diamonds/Sauce, so a reliable measure of 'tane begoneness would be worth paying for.

I figured I’d ask for another GC :slight_smile:


You could do that sort of automation using a sensitive vacuum pressure sensor.

It has to be accurate but I do it all the time when running my run to remove terpenes. The vacuum the pump pulls is inversely proportional to the amount of gas evolving from your product. For my process of removing terpenes I know the terps have depleted from the boil when the vacuum pulls down to under 5 microns. The process typically starts at 300 microns or so.

A solution would be a very accurate vacuum sensor placed as close to the oven or on it as possible. Then monitor the pressure closely. A graph helps see the down slope. When the graph bottoms out then gas has stopped evolving. Of course on my stuff the unit is sealed much better than a Vac oven but the concept should port over.

Step one after the accurate digital gauge is installed is to bring the system up to full vac and temp. This is the baseline. Anything above that means gas is evolving.

that strategy has merit, but I suspect it will be confounded by customary oven loading procedures.

I guess it might work if all the sheets in the oven were loaded at the same time, and adjustments were made for total oleoresin volume.

with the serial loading most ovens are going to see, there will usually be slabs at different states of purge as the oven is loaded over the course of the day. Folks with only a single oven are likely to have slabs that are a day or even more apart.

which suggests to me that the whole concept of monitoring the oven to determine when a slab is done is problematic. It might be possible with a single slab. or an oven loaded in a relatively short time frame. but is going to break down in real world conditions.

which leaves monitoring the slab.

so I’m still asking for another GC…or at least an upgrade so I can reliably test for solvents.


Are there any artisans who would like to contributes to the machine that replaces you?

Alright, here is my far out idea…

At a place I worked in the past, this guy had devised a “smoking machine” that he used to test his various grades of hash to determine full melt v partial melt. The basic concept, so you can visualize this goofy but useful tool, is that it was an enclosed container that pulled vacuum through a small dab rig. He could load a small amount of hash on a tool, fire it up, seal it up, and burn it down.

I’m wondering if a sensitive air quality monitor would be able to pick up ppm’s of residuals as they came through in the smoke and if that data could be correlated to actually GC/MS data to create a rough range…maybe?

Just spit ballin’ here.

IR captain!

on the head-space in the oven.
from outside the door?

talk to Big Sur Scientific.
chances are they tell you I’m nuts :wink:

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I gotta be real here with an analogy.

By now there must surely have been millions upon millions of dollars invested in the technology to remove the human equation from one of the most basic of human activities; bread making. I have lost count of the myriad very cool machines that “do it all”.

Just add ingredients, select from a few programs, push the button, and wander away. Come back and bread! right? ehhhh… wellllll.

Yes an automatic bread machine can produce something called a “loaf” and considering the millions of dollars invested in R&D this seems reasonable. Tell me though… how good on average is the “loaf” this thing poops out versus using your own oven, hands, and eyes? Let’s assume average skills here and for all the thought, innovation, and expense that went into bread machines it still just aint up to par with the human touch and never will be.

Same same methinks on ovens used to purge. Using a bread machine as a reference point, it seems no matter how much R&D might go into it the results are likely inferior to the human touch. There are just too many variables in such an open ended problem that seems so simple. Now compound that with the fact that unlike making ofbread mankind has not been purging solvents in a vacuum oven from shatter for thousands upon thousands of years. My hunch is many that want it automated may not be altogether sure how it is done manually in the first place - just like bread. Food for thought.


I’ve found that by adjusting the recipe in the bread machine, then sticking to it once optimal conditions have been found, produces a very satisfying product with minimal effort. I’ve got three growing teens, and they go through this stuff quickly.


When can I buy you dinner?


Don’t get me started on cereal!

HAHA…Our household goes threw 4-5 gallons of milk a week and like 72 eggs. LOL yeah you know we shop at costco! I know the feeling!