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Flue-curing Methodology

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Orson Carte

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I'm hoping that someone who really knows can point me in the right direction;
When flue-curing, do all the leaves have to begin the process, in the kiln, green, straight off the plant?
In other words, could primed leaves just be hung, as if to be air-cured, for a period of a week or two before going into the kiln? This would mean that the batch would be at slightly different stages of hydration when the first artificial heat was applied.
I ask this question because, with a relatively small crop (300 plants) my first priming alone would not constitute a great enough quantity to make the process economic.
(The curing 'barn' I have built is approximately a 10 foot cube and my heat-source is an electric griddle. As it's likely to be quite demanding on electricity I'd prefer to run the process as few times as possible).
So, I'm thinking it would be an advantage to treat, say, three or four consecutive primings as a single batch in the kiln. Would this work?
The other thing that I am pondering is if, say, three or four primings, at an 'average' ripeness can be taken off the plant all at the same time - and then, straight into the kiln.
Thanks.
 

deluxestogie

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The ideal flue-cure yellows leaf as rapidly as possible, then stops all metabolic processes as soon thereafter as possible. This is specifically to maximize the sugar in the leaf. Ideally, all the leaf is from the same priming, so that the point of adequate coloration is reached at the same time. This is seldom what happens.

Flue-curing takes 5 days for the early primings, and a week or so for the upper primings (since they take longer in the yellowing phase). My practice has been to begin priming when leaf tips show significant yellowing on the plant, and at each priming I take 3 or sometimes 4 leaves. As soon as one batch finishes, I prime again. So I typically do 5 flue-cure runs during one season.

One of the more troublesome issues is a single batch that does not yellow uniformly enough--often from the later primings. This presents me with the choice of producing a small percentage of green leaf, or producing no green, while ending up with more brown leaf.

I believe that yellowing at ambient temperature results in lower sugar concentrations than with the forced yellowing of a flue-cure chamber. I suspect that your decision will have to be one of final leaf quality vs. curing cost. The humidity question can be remedied by humidifying the chamber during the yellowing phase.

Have you determined that your electric griddle can actually get a 10' cube up to 165ºF?

Bob
 

Charly

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I have not done any flue curing myself, so take my words with a pinch of salt ;)
From what I have read, if you want to achieve some good results, you have to take leaves that are at the same stage of maturity and the same position on the stalk as much as possible, or you will have difficulties to know when changing temperature/humidity since some leaves will be yellow, others will be green and others might already be brown.

I think that hanging leaves to wait for flue curing them might not work well, since some leaves can become brown quickly (a few days), and you won't be able to fix there desired yellow color.

One idea : maybe you can reduce the size of your flue cure chamber ? By adding an internal separator (wall) for example.
Or you should perhaps concentrate one year on flue curing, growing more virginia plants at the same time ?

Good luck

Edit : Bob has been quicker than I :)
 

Orson Carte

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Thanks for the quick and informative reply.
In response to your query regarding the capability of the griddle to heat 1000 cu.ft to 165F - I really don't know yet. I'm still awaiting its delivery.
Its a 24x18 inch hotplate, which is rated to reach to 280degrees max, and my 10ft 'box' is actually a converted walk-in chiller, with cladded panels of 6inch foam - so, as of the moment, I'm only guessing, but hopeful.
If worse comes to worst with the hotplate I'll just have to develop a hamburger addiction.
The only other question I'd have at this stage relates to your comment about humidifying the chamber - what's easiest way of doing that? Bucket of water? Wet towels? Dedicated humidifier?
I had been led to believe that the moisture of the green material would be sufficient in itself and that it would normally be a matter of reducing humidity (through venting) rather than enhancing it.
 

deluxestogie

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Probably, the larger the flue-cure chamber, and the more homogeneous the leaf, the less you have to be concerned about adding moisture. Since the yellowing phase is run at 93 to 104ºF (typically for 2 days), and the chamber can be opened during or at the end of this phase, you could just place a large pot of water on the griddle, then remove it at the moment you begin to raise the temp into leaf wilt. I did this with my tiny, Cozy Can chamber, but did not with my much larger endoskeletal chamber.

To a large extent, flue-curing is a highly subjective art, so it may be the case that you can get the best result with your own trial and error techniques. Just remember that flue-curing was successfully performed during the 1850s, with log sheds heated by wood fires burning inside brick fireplaces, and passing the heat into flues made of iron plates. There's nothing subtle about that.

The flue-cure graphs are aspirational.

Bob
 

ChinaVoodoo

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Thanks for the quick and informative reply.
In response to your query regarding the capability of the griddle to heat 1000 cu.ft to 165F - I really don't know yet. I'm still awaiting its delivery.
Its a 24x18 inch hotplate, which is rated to reach to 280degrees max, and my 10ft 'box' is actually a converted walk-in chiller, with cladded panels of 6inch foam - so, as of the moment, I'm only guessing, but hopeful.
If worse comes to worst with the hotplate I'll just have to develop a hamburger addiction.
The only other question I'd have at this stage relates to your comment about humidifying the chamber - what's easiest way of doing that? Bucket of water? Wet towels? Dedicated humidifier?
I had been led to believe that the moisture of the green material would be sufficient in itself and that it would normally be a matter of reducing humidity (through venting) rather than enhancing it.

How many watts is the griddle? My shed is 256 cubic feet and I can reach 165F with 600W.
 

Orson Carte

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How many watts is the griddle? My shed is 256 cubic feet and I can reach 165F with 600W.

It's 2.3 kw.
I'm flying by the seat of my pants until I actually try it but my intuition leads me to believe that, because I'm heating a very well insulated 1000 cubic feet, it just might do it.
I'll let you know through this thread when I've given it a trial-run.
It's probably of little practical relevance to anyone except a NZer but here's the item: https://www.trademe.co.nz/business-...48.htm?rsqid=50755f7144854e8ca9cd827457331517
 

Orson Carte

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That's a beast. How will you be controlling its temperature? The thermostat on the griddle will not be useful for that.

Bob

I'm thinking of one of these, turning an outlet off and on. (With the griddle set near maximum). https://www.trademe.co.nz/building-...97.htm?rsqid=8a4457bc08484288838140f3a08c0986 .
I run one of these on my fermenting kiln and, despite it's cheap cost, it's worked faultlessly. There's a bit of 'lag' in the switching (sometimes the temperature overides the figure set) but you can pretty much overcome that by tinkering with the setting.
Please understand, I'm feeling my way with this and not wishing to indicate that I know for certain just what I'm doing.
 

deluxestogie

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In the US, 220 volts is provided by 3 wires (1 neutral and 2 hot), and would require a controller with 2 switching relays (to switch both hot wires). From what I can find on the Internet, NZ does use 3 wires, but only 1 of them is hot, while one is a ground and one the neutral. Only the hot wire (phase wire) needs to be switched.

The listing doesn't say if the controller has 2 or just 1 switched relay. If 2 hot wires is an issue for your power, then it would be worth verifying the number of switched relays in the device. I know they exist with 2 for a comparable price.

Bob
 

Orson Carte

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In the US, 220 volts is provided by 3 wires (1 neutral and 2 hot), and would require a controller with 2 switching relays (to switch both hot wires). From what I can find on the Internet, NZ does use 3 wires, but only 1 of them is hot, while one is a ground and one the neutral. Only the hot wire (phase wire) needs to be switched.

The listing doesn't say if the controller has 2 or just 1 switched relay. If 2 hot wires is an issue for your power, then it would be worth verifying the number of switched relays in the device. I know they exist with 2 for a comparable price.

Bob

You're right with your antipodean research; our 230/240v domestic power only has one phase (plus neutral and earth). (Mainly) industrially, we also have three-phase. There's quite a historical background to our 240 volt inclination but principally it bis based on our desire to transmit through lighter (and consequently cheaper) wires - we ain't no superpower, okay.
I do appreciate that a slightly more expensive controller, than shown, would be greatly more substantial but the unit is as cheap as chips (costs me around US$10 from an online trader/friend) and seems to be doing the job in my fermenter.
I am a bit of a tinkerer with such things but certainly don't wish to present as a know-all. I'm always ready to be re-directed and therefore really appreciative of your input.
 

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You can take this with my experience buying Dons leaf. My apartment has temperature swings and last year there was chlorophyll in the leaves. That has gone. So I would suggest that temperature fluctuations help in yellowing the leaf. That is the vapor proof bags.
 

ChinaVoodoo

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Line voltage in NZ is 240, so 2.3kW will be 9.6A. You will be pushing the maximum rating of the controller. If you can find one with higher current rating, I would consider it a good investment. At that price, I'd buy a couple as to have a backup.
 

ChinaVoodoo

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If I was you, I wouldn't spend that much on the griddle. I would get two lower wattage electric space heaters and two of those controllers. You'll save a lot of money buying cheap space heaters, and it'll provide less fatigue on the controller. Also, space heaters with integrated fans will maintain tighter highs and lows. The griddle will trip off at your set temperature but continue to heat the room as the residual heat in it continues to dissipate.
 

Orson Carte

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If I was you, I wouldn't spend that much on the griddle. I would get two lower wattage electric space heaters and two of those controllers. You'll save a lot of money buying cheap space heaters, and it'll provide less fatigue on the controller. Also, space heaters with integrated fans will maintain tighter highs and lows. The griddle will trip off at your set temperature but continue to heat the room as the residual heat in it continues to dissipate.

Thanks for the heads-up with the current draw (9.6A) . I suspected that I might be pushing the capacity of that controller to the limit - I just happen to have a few of them, and was hoping ...
I will seek out a gruntier one,if I can.
As far as the griddle goes; I've already bought it. (It's still in transit, so I can't test anything, though). I bought the griddle because I thought it might be a better heat-source than that which I use in my fermenter - (an oil column heater). I had read an old post (from AMax) suggesting that it was a good idea.
I'm in the position where I really have to get this thing going because my Virginia crop is almost ready to harvest. (We've had a phenomenally good growing season in my particular corner of the Southern Hemisphere).
So, thanks once again for your suggestions. (But, be warned, I probably have a few questions still yet to come).
 

KiwiGrown

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Hello Orson,

Funny enough I'm an Electrician living in Nelson, I'm too about to harvest my 1st small corp(Only 20 plants mind you) and use that exact thermostat for my small kiln.

You may indeed have a few problems with that thermostat, first the elements in the griddle will have an inrush current drawing anywhere up to 10x the rated current until its warmed up (Although unlikely maybe more like 50% more) and I cant find any information on what the "peak" current rating is for the thermostat so I couldn't tell if its rated for this, second running the thermostat so close to its maximum will indeed shorten its lifespan as it will generate more heat.

What I would suggest is maybe try starting the griddle on low and working up, The griddle may have more then 1 element, elements don't operate low or high there rather on or off, so by starting low and working up hopefully it has more then 1 element so you can limit the inrush current, it may have just 1 element and a thermostat is located on the hotplate to control the heat, if that's the case starting low won't help.

The best thing you can do to help limit the damage the heat will cause the thermostat is cooling it, maybe with a computer fan.

Hope this help
 

ChinaVoodoo

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Hello Orson,

Funny enough I'm an Electrician living in Nelson, I'm too about to harvest my 1st small corp(Only 20 plants mind you) and use that exact thermostat for my small kiln.

You may indeed have a few problems with that thermostat, first the elements in the griddle will have an inrush current drawing anywhere up to 10x the rated current until its warmed up (Although unlikely maybe more like 50% more) and I cant find any information on what the "peak" current rating is for the thermostat so I couldn't tell if its rated for this, second running the thermostat so close to its maximum will indeed shorten its lifespan as it will generate more heat.

What I would suggest is maybe try starting the griddle on low and working up, The griddle may have more then 1 element, elements don't operate low or high there rather on or off, so by starting low and working up hopefully it has more then 1 element so you can limit the inrush current, it may have just 1 element and a thermostat is located on the hotplate to control the heat, if that's the case starting low won't help.

The best thing you can do to help limit the damage the heat will cause the thermostat is cooling it, maybe with a computer fan.

Hope this help

That sounds like good electrical advice but the heat will be cycling on and off repeatedly for several days.
 

Orson Carte

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Hello Orson,

Funny enough I'm an Electrician living in Nelson, I'm too about to harvest my 1st small corp(Only 20 plants mind you) and use that exact thermostat for my small kiln.

You may indeed have a few problems with that thermostat, first the elements in the griddle will have an inrush current drawing anywhere up to 10x the rated current until its warmed up (Although unlikely maybe more like 50% more) and I cant find any information on what the "peak" current rating is for the thermostat so I couldn't tell if its rated for this, second running the thermostat so close to its maximum will indeed shorten its lifespan as it will generate more heat.

What I would suggest is maybe try starting the griddle on low and working up, The griddle may have more then 1 element, elements don't operate low or high there rather on or off, so by starting low and working up hopefully it has more then 1 element so you can limit the inrush current, it may have just 1 element and a thermostat is located on the hotplate to control the heat, if that's the case starting low won't help.

The best thing you can do to help limit the damage the heat will cause the thermostat is cooling it, maybe with a computer fan.

Hope this help

I'm not sure that I'm going to be replying to aspects you've raised. But here's a handful of thoughts -
* I've been running that same model of thermostat with my fermenter. The required temperature there is considerably lower than the highest temperature demanded in a flue-cure, and I'm only running one standard oil-column heater, but so far, I've had no trouble at all.
* Are you thinking that I will have the programmable controller inside the chamber?
I don't intend that to happen. Only the griddle will be inside , subject to the heat. (And a fan and light on separate circuits). The controller will be outside and in the air.
*Since my last posting I have been given (I think it's just called) a 'relay' - which is wired into the circuit coming out from the controller, and then on to the griddle - I'm told, by my friendly heating/refrigeration electrician that this reduces the load on the actual controller to virtually nothing.
Thanks for your input - and welcome to the Forum.
 

KiwiGrown

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A relay will help a lot, it doesn't reduce the load of it running(It will still draw 9.6A though the unit), it handles the grunt work of the initial switch when the stat turns on the griddle (the inrush current I was talking about). If you have been running a Oil-Column off it without hassle I would think it should be fine, a typical Oil-Column is 2000w anyway.

I assumed the thermostat wasn't inside the chamber anyway I thought it was worth noting if you are worried about it dying the main reason it would do that is because its running to hot.
 

KiwiGrown

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Sorry, I'm a fool, Yes your right the thermostat will have almost no load it's just switching the relay. I was thinking about this the wrong way.
 
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