deluxestogie's Trash Can Cozy Flue-cure Chamber

[deluxestogie]

PART I: A Poor Man's Flue Cure Problem

Flue-curing tobacco takes primed leaf from ripe to fully cured and ready to smoke or pack in 5 days. (Flue-cured leaf is not really helpful in cigars, but is a highly regarded, major blend component in cigarettes, and a common minor or major blending component in pipe tobacco.) The goal is to yellow the leaf at lowish temperature (87-104ºF) for two days, dry the yellowed lamina at a moderate rate (rising up to 135ºF) for a day, then completely crisp-dry the stems at a high temperature during the remaining two days (taking the temp up to 165ºF). The final temperature (prolonged at greater than 149ºF) is always high enough to break down the leaf's oxidase enzyme, which prevents the rapid browning process of aging. A much slower enzyme, a peroxidase, survives up to 191ºF. Some regimens go as high as 200º, which halts all further aging changes, but may caramelize some of the sugars, giving the leaf a burnt taste. My goal is a temp of ~165ºF by day 5, which would hopefully preserve bright-colored leaf, but still allow gradual aging.

Flue-cure varieties have been selected over the last century and a half to yield the best bright leaf. Since the idea is to "fix" the sweetness and bright color of the leaf, it should be leaf-primed when fully ripe (somewhat yellowed in the field). Once leaf has begun to brown, no amount of flue-curing can restore the bright color.

This is the simplest, safest and cheapest flue-cure chamber I could think up. The leaf capacity is low. It is actually a variation on my trash can fire cure chamber. While the latter had holes drilled into the bottom to admit smoke from atop a Brinkman Smoker, the flue-cure version has a solid bottom, is insulated, and uses a 2 quart Crock Pot as the electrical heat source. There is no fan. It relies on convection. Primed leaf is strung on 2' segments of wire and hung on a removable angle iron. Capacity is 30 to 75 leaves, depending of leaf size (actually depending more on stem thickness than leaf length and width). This is the equivalent of two to 5 entire plants. Moisture escapes by adjusting the fit of the lid. Temperature adjustments are made manually, using the thermostat set screw.

The can is a 31 gallon galvanized steel trash can.

The required parts come to roughly $100.

• galvanized steel trash can and lid (~$25)
• two 2" bolts, with two washer each and two nuts each
• two small bolts with one nut each that will fit the two mounting holes in the thermostat
• an angle iron (perforated) long enough to match the diameter of the upper rim of the trash can ($3-$6)
• a 180ºF water heater thermostat (less than $12)
• a grill thermometer (~$15)
• a fiberglass water heater blanket (~$25)
• a roll of metal waterproofing tape (~$7)
• a 3-conductor outdoor-rated extension cord
• a 3.5" piece of 3/8" Tygon tubing
• a 2 quart Crock Pot (~$10)

The construction requires:

• drilling 6 holes into the trash can:
  ---a 1" hole near the interior bottom for the heat source (Crock Pot) power cord
  ---a 7/8" hole for the grill thermometer
  ---one hole for each of the two angle iron support bolts on opposite sides of the upper land
  ---two small holes for the thermostat mounting screws
• measuring and cutting the angle iron with a hacksaw
• mounting the grill thermometer (requires a wrench and a channel-lok pliers)
• wiring the thermostat
• lining the drilled power cord hole edge with a segment of split Tygon tubing (after passing the Crock Pot cord)
• cutting, wrapping and taping a segment of water heater blanket around the can
• cutting and taping a round pad of water heater blanket on the lid

The thermostat is an "industrial" water heater thermostat that reaches 180ºF (unlike current residential water heater thermostats, which are limited to 150ºF).

Thermostat source: http://www.plumbingsupply.com/elements.html#thermo item# 08314, for $11.67.

The angle iron support bolts that I used are 3/8"x2", but they just need to be sturdy enough to support the weight of green leaf attached to the angle iron, which actually rests on the twin nuts of each bolt. I place a washer on either side of the trash can metal through which the bolts pass. The shape of the upper land of the trash can makes this resting angle iron quite stable. Cut the length of the angle iron so that it just barely fits inside the can with a little effort.

While the grill thermometer has a short probe that extends into the trash can, the thermostat is entirely outside the can, with its back side held firmly against the can metal by two small mounting bolts.

In drilling the power cord hole, keep in mind that the inside bottom of the can may be an inch or more higher than the outside bottom of the can. The segment of Tygon tubing is to prevent the sharp edge of the hole from chafing the power cord. Split the tubing along its length on the outer curve (if it comes coiled). I used tin snips to remove plastic flanges that surround the Crock Pot plug, so that it would pass through a 1" hole. The cord should be passed before inserting the segment of Tygon, otherwise the plug won't fit.

The extension cord insulation must be carefully split to gain access to the three individual conductors.

The "hot" wire is the only one that is cut. Its insulation (black here) is stripped on either cut end, then screwed into the thermostat terminals. The neutral (while white here, it may also be colored, but will have stripes or some other indexing marking) is left intact. The green ground wire has not been cut, but the insulation stripped away where it passes the thermostat mounting bolt, which is loosened, then tightened to grip the ground. This ground now grounds the entire trash can for electrical safety (provided you actually plug the extension cord into a grounding--3 prong--outlet.)

Continued in Part II.

 

[deluxestogie]

PART II: A Cozy Can Cure

The device is now complete. What remains to be done is to apply the insulation. I had hoped to locate some rock wool for this, but had to settle for a fiberglass water heater blanket. This particular brand comes folded lengthwise and rolled. Included in the package are a number of long strips of white vinyl tape, which I used to tape the wrap together. The length was perfect for the circumference of the trash can. One-half the width was right for the height of the trash can, keeping the free margin of backing at the upper edge of the can's top land.

I needed to cut slits with scissors into the blanket to accommodate the trash can handles (so they could be used), the grill thermometer, the thermostat and the power hole at the bottom. The slits were closed with the vinyl tape, with the exception of the slit over the thermostat set screw. Here I used the vinyl tape to line either edge of the opening, to prevent exposing fiberglass while setting the temperature, but allowing the edges of the slit to come back together after setting it.

Now came the nasty part--taping the blanket to the upper land of the trash can, as well as attaching the lid pad to the margins of the lid. The metal waterproofing tape is used for this. It uses a stretchy, tenacious butyl adhesive that will get all over your fingers. Be sure to purchase some Goo-Gone ahead of time for cleaning the adhesive off your fingers.

In my initial empty-can trial, with the 100 watt 2 quart Crock Pot set to "Low," it reached a 110ºF initial stage in about 10 minutes. This was high for the yellowing stage. My hope was that loaded and vented, the low wattage heat source would stay below 105ºF for the first 36 hours.

Adjusting the thermostat set screw, the can rose to 165ºF in about 1 hour--with the Crock Pot still set on "Low!" This seems to be pretty much the upper limit on "Low." The Trash Can Cozy runs while standing inside my enclosed back porch. As for the heat, it's just a small Crock Pot, with crockery in, but no lid or liquid. So the risk is low.

After running it at 165ºF for 24 hours, and following a quick inspection, I strung 16 fairly ripe VA Bright lugs onto the angle iron, added a string of 12 Big Gem lugs, and loaded it into the can. It would fit more, but that was the limit of the leaf that appeared ready. (Although I have been using tags cut from Tyvek for labeling my hung leaf this year, I opted for wood tags on the strings that would go into the Cozy.) Because of the long length of the leaves, and the short length of the trash can, the best I could do with preventing the Crock Pot from toasting the nearby leaf was to make sure none of the leaf tips were actually inside the Crock Pot.

The 2 quart Crock Pot. In the right image, one string (wire) of leaf was hooked onto the angle iron, then the second string attached alongside it.

Humidity and air flow are carefully controlled by a strategically placed clothespin. Temperature adjustment is done with a screwdriver, through the peek-a-boo gap in the cozy blanket.

In practice, I ran the cure with two clothespins, positioned 6" apart.

My planned schedule, by DAY:

1. ~87-104ºF
2. ~87-104ºF (maybe continue yellowing to 60 hours total, depending on leaf color)
3. ~115-130ºF
4. ~135-145ºF
5. ~150-165ºF

Note that this is just a pie in the sky schedule of temperatures, since the thermostat is probably cycling with an error of about 7or more degrees F above and below the set temperature.

I nudge the temperature upward one or two times a day, depending on the readings. [Instead of precise Arduino microprocessor scheduled temp control, I'm substituting imprecise arduous manual screwdriver temp control. [Set it, and don't forget it! With apologies to Ron Popiel.] The water heater thermostat is, I suppose, about as inaccurate at controlling the temperature as the wood fires of the old flue-cure barn brick furnaces. My guess is that those old barns were heated at "low fire," "medium fire" and "hot fire," in sequence, over the five days of the cure.

Within a few hours of starting the cure (thermostat set to its lowest setting, which is regretably 120ºF), a mild aroma similar to cooking green beans is noticeable. This aroma began to fade by the third day. Unfortunately, as I discovered later, the leaf was actually cooking. Very early on, I lifted the lid and glanced inside the can (where I saw leaf yellowing nicely), but decided to avoid disturbing the heat/humidity balance by any further inspections for the duration of the cure. As an aside, the presence of aroma is an indication that there are convection currents within the can.

I discovered that, at the lowest thermostat setting, the temperature stabilized at about 115ºF, even loaded with leaf and vented. Without further adjustment, the decrease in evaporative cooling of the green leaf allowed the temperature to slowly rise to about 120ºF by early in the second 24 hours. This is, of course too high for yellowing safely. At the end of 48 hours, I gave the set screw a tiny upward adjustment (marked as 125ºF), so that by mid-way into the third day, the can temp was running between about 130 and 135ºF. Some minimal condensation was present on the raised edge of the can lid during the second day. By early in day three, this was nearly gone.

Failure

By 72 hours (a point at which the lamina should be dry), I went ahead and inspected the doomed leaf. The surprise was that some of the leaves (two, and probably the two that were the yellowest at the start) were actually flue-curing correctly. All of the Big Gem had dried to a grayish olive green. The VA Bright seemed to fare better. Perhaps it was riper to begin with. The results were considerably worse than leaverhead's first run (using a converted 55 gallon drum rigged to a heat gun).

I decided to remove the leaf, and begin again using a different heat source for the first few days. To bring the dried leaf back into case, I simply added a cup of water to the Crock Pot, closed the lid, and waited a couple of hours for the lamina to rehydrate.

The temperature problem with the yellowing should have been obvious ahead of time. The water heater thermostat doesn't know about temperatures below 120ºF. Sometimes my optimism outruns common sense.

I did stem the most golden leaf from this failed cure. It offered the distinct aroma of cigarette tobacco, and when wrapped in a neutral-flavored segment of Ecuador CT Shade, it puffed like, taste like and smelled like a cigarette. Very mild. Against my better judgement, I inhaled a few puffs, and found that it was mild and non-irritating. So the fundamentals of this failed curing process produced a single, successfully flue-cured leaf. I was on the right track. I'll try the Big Gem "candela wrapper" some time soon.

Continued in Part III.

 

[deluxestogie]

PART III: Cozy Can Cure--Second Attempt

Since I had two Hydro Farm 9" x 19" seedling heat mats (17 watts each; ~$25 each, on sale), I placed them on edge, wrapping on the bottom of the inside of the cozy can. Their power cords were passed out the top (between the two clothespins) and plugged directly into the thermostat outlet, since it will not interrupt the power at the lower temperature. With the Crock Pot unplugged, the seedling mats provide a lower wattage for the yellowing phase. These are slipped out of the can (along the sides) at the end of the first 48-60 hours, and the Crock Pot then plugged into the thermostat for the remaining cure.

For another $50, the seedling heat mats could be controlled precisely with a probe-equipped digital thermostat designed for use with them,
http://www.charleysgreenhouse.com/i...ils&productid=8043&cid1=-99&cid2=-99&cid3=-99
but I don't think it needs to be that precise. Only the yellowing phase seems to need such careful attention to the temperature.

In a trial run, with the cozy can empty, one seedling mat powered brought the temperature to a stable 95ºF--perfect. The cozy can was filled, this time with 16 leaves of Silk Leaf and 16 of Paris Wrapper (actually classed as a flue-cure type). It looks like it could hold a little over 40 leaves of these two varieties. Every few hours or so, I unplug one seedling mat and plug-in the other, so that alternating sides of the can have greater heat. Both mats running simultaneously brought the temp to just over 102ºF, which I find uncomfortably close to the 104ºF max temp for yellowing. So...just one mat at a time. With a lot of fuss, a single mat could go under the Crock Pot, to provide more even heat, but I worried that it might be a problem to extract it following the yellowing phase. Perhaps the digital controller for the heat mats would be useful in this regard.

After 60 hours, the leaf on either side of the can (where the seedling mats are located) was adequately yellowed, but the leaf in the center of the can still showed some green.

I plugged in both mats for another 12 hours of yellowing (total yellowing time 72 hours). At that point, I easily removed the two seedling mats (since the leaf is still moist and flexible), and connected the Crock Pot, which brought the temp to ~120ºF over about 2 hours.

For day 4, the temp was kept between 135 and 145ºF. During the final 24 hours (with the Crock Pot still on the "low" setting), the thermostat was cranked to its max. The Cozy Can reached 160ºF. Six hours before completion, I draped a fleece jacket over the top, which was just enough to stabilized the temp at 165ºF.

Unable to wait for the leaf to fully come into case, I carefully removed it and snapped this photo.

After the complete cure process, a cup of water can be added to the still-warm Crock Pot, the lid of the can closed, and the cured leaf allowed to rehydrate for 3 hours.

I'll post nicer photos of the range of leaf colors tomorrow.

All the flue-curing chemistry you could want: http://www.tobaccoscienceonline.org/doi/full/10.3381/0082-4623-44.1.51

Summary:
The Trash Can Cozy is capable of performing a workable flue-curing process in 5 to 6 days, on a batch of 40 to 75 leaves. The construction is tedious, but technically simple (and you end up with a puffy, trash can size object to store somewhere during the winter). The cost, as described here, is under $150. The device is easy to operate, uses negligeble electricity, and is a reasonably safe thing to operate indoors. Since it can flue-cure the primed leaf of roughly 3 entire plants per run--approximately 3/4 to 1-1/2 pounds of finished leaf [that is, in the ball park of a pound of finished leaf a week], its scale is suitable for a home grower. A potential bottleneck rests in the maturity dates of your harvest, since the leaf needs to be flue-cured when it's ripe. But as a supplement to the usual air-curing of a home crop, it just might be useful.

Bob

 

[Chicken]

5 days...

for 75 leaves,

looks like you built a winner,

i have seen this device you built, at that other site,,

very effeciant,

 

[deluxestogie]

i have seen this device you built, at that other site...

Chicken,
The HTGT post is about a fire-cure chamber, and an idea for a flue-cure chamber. This flue-cure chamber was started about 2 weeks ago, after pondering many options for the past year.

Bob

 

[BarG]

Incredible Bob. It will take all night to read and digest though, But The results speak for themselves.

 

[johnlee1933]

Nicely done Bob.

John

 

[leverhead]

Excellent! You got it! I guess I worry too much. I knew this was a good group to hang around with!

 

[deluxestogie]

But Wait! There's More!

For storing this sizable contraption in winter, the answer is simple. Don't store it. It's a kiln large enough to process whole leaf. So, after the flue-curing season, it will function as a medium size, Crock Pot based kiln, with no alterations. Just omit the seedling mats. Same low power consumption. The only tricky part, and that only on the first run, is to determine if and how much to vent the lid. I believe that for kilning, color-cured leaf could be hung more densely, say 3 or 4 strings of 24 leaves each.

So, build a flue-cure chamber; get a kiln for free!

In the daylight tomorrow, I'll photograph the flue-cured leaf. After bringing it into case, and carefully examining the leaf, I find the following:

• Of 32 leaves, 3 leaves of one variety (Paris Wrapper) dried to a light green. They were in the center of the can.
• 4 of the Silk Leaf dried somewhat browner than ideal.
• Most of the leaf is a lemon yellow bright cure.
• The leaf exhibits a leathery texture, with fully dried stems.
• It's damn pretty stuff.

Bob

 

[Tom_in_TN]

Bob, your 2 in 1 Flue-Cure/Kiln Chamber is awesome and a definite refinement/improvement on your earlier project posted at the other site. Very interesting work you did and seems simple enough that dummies like me could copy (maybe).

 

[Chicken]

i didnt realize, it was a whole different system,

but it also, looks very effective,

 

[indianjoe]

Wow Bob,
excellent work and write-up!

 

[Matty]

I'm going to try growing a few plants next year. I live in an apartment. This curing chamber would be perfect, I just have to figure where I'm gonna grow the plants! lol

 

[deluxestogie]

The flue-cured leaf.

There is no sunshine today, so these photos were taken under an overcast sky.

First, the good news.

Bright-cured Paris Wrapper.

The range of color in the leathery Paris Wrapper leaf.

This Silk Leaf, which flue-cured in the very same batch as the Paris Wrapper, came out somewhat browner.

And finally, the bad news.

These three leaves cured green.

When I went out to my enclosed back porch, where this leaf had been hanging overnight, it smelled like a giant cigarette.

Bob

 

[driftinmark]

why do i have the feeling that home depots all over are gonna be selling galvanized trash cans like crazy now........imma have to wait till next weekend when I get off work, but definetly gonna do this Bob..thanks,

I was reading about leverheads flue cure chamber also, its very nice too.......but this will be a little easier for me to build

 

[Michibacy]

Bob this is very similar to what I built last season, wasn't nearly this intricate but it did nearly the same thing. My mom stole my kiln and used it for it's labeled purpose p) so I may need to purchase a new one, that, or I do have some timber left over I might just build a kiln with.

 

[leverhead]

Well I'll make it official, right now, you have flue cured more leaf than I have! What did this batch smell like when it was curing? Nice hands too!

 

[deluxestogie]

If you plan to set up a Cozy Can flue-cure chamber, remember that the home improvement stores are not likely to carry the required thermostat. You will need one that can reach at least 165ºF+. You will probably have to order one on-line, using the link posted in the "parts" section of the thread. Also, the crucial solution to yellowing at low temperature requires at least one 17 watt (9" x 19.5") seedling heat mat (probably two), also not usually available at retail stores this time of year. They can be found at:

• http://www.johnnyseeds.com/p-8077-hydrofarm-seedling-heat-mat-9-x-19-17-watts.aspx
• http://www.growerssupply.com/farm/supplies/prod1;;pg103644_103644.html
• many other on-line nursery suppliers

The seedling mat(s) can, of course, be used in the spring for germinating seedlings.

Bob

 

[wazzappenning]

i thought for sure that they wouldn't carry a galvanized garbage can either. isn't everything china plastic now? i don't remember seeing one in a store, but then again, ive never looked for one either.

 

[deluxestogie]

If you recall, my first flue-cure attempt "failed," but did produce a whole string of Big Gem green leaves. I brought one into case, stemmed it, and used it as a candela (green) cigar wrapper--which is just what I had accidentally created. From the late 1940s through the early 1970s, most of the cigars sold in the US were candela wrapped. They were tagged "AMS," for American Market Selection. Today they are often called "double claro."

I expected the green leaf to have a bitter taste on the tongue. Instead, the tough, stretchable candela wrapper rolled nicely, burned well, and contributed practically no taste at all--unlike air-cured leaf that dries green. It's like smoking a cigar in a cigar holder that's chewy. Although candela cigars are not my preference, this one surprised me with a pleasant smoke. The filler was aged, air-cured Maryland. I would guess that if you rolled cigarette shred in a candela wrapper, it would smoke pretty much like a jumbo cigarette that you can clench in your teeth.

Anyone with a kiln can make candela leaf in 3 or 4 days. Green leaf is held at about 115-120ºF for two or three days, until it begins to dry. Then the temp is taken up to about 135ºF for a day to completely dry the lamina and veins (though the stem will not be fully dried at this temp).

Bob