Bho darkens while purge

Last run I had about 3oz of bho separated evenly on 3 trays in my vac oven, I flip every 12 hours initial temp at 85F. I go up in temp incrementally over 3 days but noticed on the third day that my bho had darkened? Any info on what could have caused this to happen? The oven is sanitized after every batch so I don’t think it could be contamination but I might be wrong.

Did u run the material at cryo temps, along with solvent and everything…

Next have you checked behind your oven to make sure your temps are correct… Sounds like you got to hot… By darken do you mean as dark when decarb…or just lil darken golden… The thicker it is the darker she’ll look also

Get a calibrated temp thermometer and set your oven for 20 mins… then check temp. If off just remove temp gauge and turn it to set temp ovens dont always heat to temp set on dial so calibrate it

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Dewax at -55F and solvent just a tad bit warmer I’m going to try and calibrate my oven and make sure temps are steady thanks!

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Could you explain a little better please how do I prove the oven?

I recommend the search function… Search results for 'calibrate oven' - Future4200

top hit? Oven tek SOP criticisms welcome - #5 by Killa12345

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Start your oven set it to 250. After it reaches temp put a thermometer in for a few minutes then check the temp if it says 250 you are good. If not you will have to adjust gauge to new temp shown on thermometer

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Gotcha thank you :pray::raised_hands:t3:

There is no way a vacuum oven can reach stable temps in 20 minutes unless the temperature you want to achieve is exactly that, or near that of the room.
Allowing the oven to heat up with atmosphere in the chamber can result in a significant temperature drop when heated atmosphere is evacuated from the chamber. To achieve the best temperature stability and uniformity, allow the oven to heat up under vacuum prior to loading product. This heat soaks the oven body and insulation masses.

The oven has to rhythmically predict what the temp is by pulsing the heating elements on and off (you cant just set the elements on ‘medium’, they are all the way on or all the way off) and whatever internal temperature sensors have to wait to feel the heat before knowing if it should apply more or not. This makes ramping up a pain for the ovens, especially with product absorbing energy and keeping a sane temperature uniformity throughout the chamber (even heating across all shelves)

Depending on size, you should preheat under vac for at least 2 hours. When you do your ramping this is where you’ll have the largest risk of overshoot.

I see your exact issue a lot

A couple questions:
Does the room temperature change when you leave at night
Where is the temperature sensor on/in your oven?

Explanation: Most china ovens are calibrated in a 70 degree room, for a 70 degree room. These units have no temp sensor in the oven chamber, how could it possibly know accurately what the temperature is when the sensor is on the outside of the chamber? Monkey business. The oven has no idea the ambient temperature has changed by x degrees, with no secondary sensor, or direct chamber sensor there is no way it can ‘know’ the ambient temperature has changed to adjust its heating pattern. It thinks this is a change in the oven chamber and compensates by changing its heating plan (or even worse, not), causing your overshoot.

Must be warm where you are, and you’re turning off your AC. You will notice when you get to calibration, a 10 degree change in ambient temperature will mean a 10 degree or more offset from your calibrated center. This is a common issue with China ovens.

As far as calibration: For best results, use a digital device with thermocouple probes. Never use alcohol or mercury based thermometers! Obviously there is no way to use IR/laser sensors of any kind. See your ovens manual for recommended calibration tek.