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Yellowing Phase

ChinaVoodoo

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It is pretty consistent that flue curing schedules include a yellowing phase between 90°F and 110°F. Is the sole purpose of this to gain colour consistency within all the leaves in a batch, or is there some other reason?

I ask because a lot of people pile at ambient temperature until yellow, then jump strait into the higher temperature stages.
 

deluxestogie

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Gist: Faster yellowing = sweeter finished leaf.

Yellowing phase, in the chart that I use, is held at 100°F. I try to hold it between 96°F and 102°F. Natural sugars within any variety leaf (maple, tobacco, etc.) are slowly consumed in a separate process, which is at a fairly steady rate, so long as the lamina remain alive. As the chlorophyll breaks down, the already present xanthophylls and carotenoids reveal the yellow to orange color that has been masked by the chlorophyll. Yellowing at 100°F is an attempt to accelerate the breakdown of chlorophyll, while reducing the time during which background metabolism within the leaf is consuming sugars and other carbs--a consumption that continues until the leaf is dead. My understanding is that the added heat accelerates chlorophyll breakdown more than it accelerates the metabolism of sugars. That would imply that longer duration yellowing would lead to less sugar retained in the finished leaf.

Temps above 104°F (if I recall correctly) accelerate leaf death, and is not an intended part of the yellowing phase. Some members have been quite happy with results from yellowing at higher temperatures.

Bob
 

plantdude

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As a spin off from the question, what are some thoughts about yellowing before sun curing?
 

johnny108

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W
Are you asking about flue-cure varieties that are to be sun-cured? With regard to Orientals, pre-yellowing helps in ambient conditions that are too dry to properly sun-cure.

Bob
What metabolic changes occur in sun curing? Is it similar to flue curing? Or, is it an in between method of other curing practices?
 

Frelono

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I've been wondering this myself. Can i keep the cure chamber in dry off mode and just hang in leaves as soon as I get them yellow? I found it easier to controll the yellowing "manually" leaf by leaf than all together in the chamber.
 

deluxestogie

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  • Flue-Curing - Lower pH and highest sugar content: Rapidly yellow the leaf, then fully dry as rapidly as possible.
  • Sun-Curing - In between: Yellow the leaf in the direct sun, then allow to fully dry in the sun.
  • Air-Curing - Higher pH and lowest sugar content: Yellow the leaf in the shade (e.g. in a shed), then allow it to color to brown, prior to fully drying
  • Fire-Curing - same as air-curing, but accompanied by intentional exposure to smoke
All leaf will eventually yellow, if not permitted to fully dry (die).
Bob
 

johnny108

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  • Flue-Curing - Lower pH and highest sugar content: Rapidly yellow the leaf, then fully dry as rapidly as possible.
  • Sun-Curing - In between: Yellow the leaf in the direct sun, then allow to fully dry in the sun.
  • Air-Curing - Higher pH and lowest sugar content: Yellow the leaf in the shade (e.g. in a shed), then allow it to color to brown, prior to fully drying
  • Fire-Curing - same as air-curing, but accompanied by intentional exposure to smoke
All leaf will eventually yellow, if not permitted to fully dry (die).
Bob
Where does dashboard curing fit into this? An improvised sun cure?
 

johnny108

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Sun curing
Dashboard curing is attempting to cure leaf in wildly unpredictable conditions of temperature, relative humidity and direct sun exposure. My home-grown tobacco requires too much labor for me to have ever been tempted to try dashboard curing.

Bob
Sun curing seems to require sun, something lacking in Northern Europe. Could a terrarium, or other similar enclosure with better controls than a car dashboard, be used- a sort of transparent sun curing kiln?
What are the ideal temps and humidity for sun curing? Is full, constant sun needed? Is it just the heat, or is ultraviolet radiation taking part?
Too many questions while I’m stuck at work!
 

deluxestogie

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What are the ideal temps and humidity for sun curing?
Full sun; relatively high humidity.
Is full, constant sun needed?
I have successfully "sun-cured" during 3 weeks of constantly overcast sky. My sun shines only during the daytime.
Is it just the heat
Sunlight. It is the light.
Could a terrarium...
What variety are you hoping to cure? What use will you have for it?

Bob
 

johnny108

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Full sun; relatively high humidity.

I have successfully "sun-cured" during 3 weeks of constantly overcast sky. My sun shines only during the daytime.

Sunlight. It is the light.

What variety are you hoping to cure? What use will you have for it?

Bob
Tonight’s forecast: dark.
(Dammit)
Varieties are Xanthi, Rot Front, and Geudertheimer.
Wanted to try different curing techniques with each variety.
Use? Whatever it ends up suitable for. I’m not trying for a specific product- cigarette, pipe, etc., just something useful and good in at least one style. And if it all tastes terrible, it can be dried, powdered, and blasted with mint flavoring into snus.
 
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