Kiln ideas

[Moth]

My plants are doing well, I'm collecting the suckers and practicing colour curing in a box and thinking about a kiln. Finding an old fridge and gutting it fine, although, unsure how to control the temp and humidity.

Can you please read my understanding below and let me know if I'm wrong, or missing anything?

1) crock pot (slow cooker) and 'stat.
- Simplest and cheap (£9 slow cooker, £10 stc1000 controller)
- Requires daily top ups and "trial and error" humidity calibration (how much of the lid is open)

2) heat lamp, atomiser and dual stat
- Simple and cheap (£8 heat lamp, £11 sht2000 dual relay temp and humidity controller, £6 atomiser)
- not sure if happy with the heat lamp in a box, although could sub with a £20 oil filled bar heater for greenhouses)
-atomiser and hard water don't play well (I have very hard water)

3) arduino controller instead of an stc1000/shc2000 and parts from either #1 or #2
- most complex (I already own a few and the only investment is time, coding isn't a problem)
- can add additional data logging (although, in real terms a min/max temp and humidity would be fine)
- can automate a vent fan if either temp or humidity exceeds a cutoff

I've read a number of threads about kilns, although, there's frustratingly little information about non crock pot kilns / dual temp and humidity controllers etc

Any thoughts / pitfalls about my understanding of the possible build options?

 

[deluxestogie]

frustratingly little information about non crock pot kiln....

It's easy to climb into the $1000 range for a kiln. @DrBob's concept for using a Crockpot as a combined heat and humidity source (~10 years ago) was so simple and safe and functional and practical, compared to the alternatives, that it was immediately adopted (and improved) by the vast majority of those who built a kiln during the subsequent years. The initial controller was a hot water heater thermostat (sloppy but functional). With suitable digital controllers increasingly available and increasingly inexpensive and convenient, those are most commonly used now.

With a Crockpot kiln, the frequency of needing to add water depends on how well you seal the kiln you build AND the adequacy of its insulation. The better the seal, the longer the water lasts. It's also dependent on the ambient temp. Some folks have their kilns in a shed or in the garage. The warmer the ambient temps, the longer the water lasts. (My kiln is situated in my enclosed back porch, which is always open to the kitchen. It uses less water in summer than in winter. My range is a refill every 3 to 5 days. I leave the lid off during 100% of the run.) The Crockpot controls need only to set the applied wattage to low or high. As an appliance, a Crockpot lasts for between many years and eternally. With hard water, the scale usually needs to be removed every year or two. (Boil 50:50 vinegar in the Crockpot for a day, then scru-a-dub.)

I have felt no need to move up to using an Arduino board, since the only real advantage would be during the kiln's use as a flue-curing chamber--about 6 weeks per year, and only if I grow flue-cure tobacco that year. Flue-curing follows a timed regimen of temperature adjustments during each 5-7 day run. The charts assume adjustments at 2 hour intervals, though I've gotten excellent results with the far more convenient 12 hour interpolated intervals. During routine, 5 or 6 week cigar leaf kilning runs, the set temp and hysteresis never change, so an Arduino would just sit there wondering how to pass its time.

One requirement of the Arduino, is that you would need to add at least one relay capable of frequently handling loads of up to 2 or so Amperes (depending on the rating of the heat source). The cheapie digital controllers have a built-in relay with a sufficient rating.

In kilning temps above 122°F, mold can not grow. (I currently use a set point of 128°F +- 5°.) So the measurement and regulation of humidity is not helpful. So long as the leaf stays flexible, the enzymatic changes are happening. This happy state depends on relatively equal temp distribution throughout the chamber. To this end, a circulation fan (moisture tolerant--such as a bathroom ventilation fan) is a wise addition.

So, you can certainly go with a more complex arrangement, maybe even duplicating the functions of a commercial Roanoke barn. I would cast my humble vote for a well-sealed and well-insulated box, a Crockpot (I currently use a 6-quart one.), a circulation fan and a cheap digital controller.

Bob

 

[Jitterbugdude]

Crockpot is the simplest way to go. If you do not have a large harvest you can use my method and put your leaves into a container (glass jar, plastic bag etc). With your leaves in a container the only thing you have to worry about is heat.

 

[Charly]

As Bob said, you could build as complicated as you want (it can be a fun project to create and program your arduino to control your kiln/flue curing chamber !) but simple methods can already you give good results.

I use Jitterbugdude method (I was worried about having humidity and electricity together in a closed box in my house...) : my tobacco is in glass jars, and the kiln heat source is a 150W bulb with a controller to switch on/off when the temperature is too low or too high.
Add a bathroom fan (blowing directly on the bulb) and a couple other fans to help the temperature to distribute more evenly in the whole kiln, and that's it.

 

[Moth]

Thank you all, just what I needed to hear.

Sure, I can play with toys, although it won't make any difference to the end result.

My life is busy enough, and there are more productive ways to spend my time - even if it's just relaxing...

I'll keep it simple - the £11 shc2000, and only use it to control the heat - I'll use the humidity controller as a display only (so the digital readout will show me the temp and humidity in the kiln).

Whether I use a crock pot or glass jars will depend on how large my leaf gets, and, how much I end up with.

Yesterday I watched 45mph/71kmh winds batter the garden. Pleasantly surprised this morning to find none badly damaged, although, they all look tousled.

 

[deluxestogie]

When I designed my latest kiln, a number of years ago (the endoskeletal kiln), my assumption was that I would always wish to hang my strung leaf within the kiln. This is indeed a requirement for flue-curing. [Leaf can reach over 30 inches in length. So the chamber needed at least one tier with a 30" height.] But the vast majority of the kiln's time is spent kilning (fermenting) leaf, rather than flue-curing. For fermentation, I now cram well-cased whole leaf into ~24" x 36", heavy-duty, clear plastic bags [tops left OPEN], which I then either stack on the wire shelves or suspend with clothespins from the bottom of the shelving. This approach allows me to kiln nearly four times as much leaf per run, and the case of the leaf is unaffected by having to open the kiln door every few days.

This newer modality of using the kiln suggests to me that the kiln dimensions for dual use result in a compromise of ideal flue-curing dimensions vs. most efficient kilning dimensions.

If you read my initial design thread on the endoskeletal kiln, one of my justifications for some of structural complexity of the screwed, wood frame design was that it could be disassembled into flat, storable panels when not in use. Ha! Not only has it never been disassembled since then, it hardly ever gets moved (Ah! Handy swivel casters.) from its near-permanent station.

I was clearly too clever. The kilns general concepts are still valid, but in retrospect, it could be made simpler. One other revelation is that XPS foam chronically exposed to direct sunlight will gradually turn to dust. The back of the kiln, after several years of exposure appears faded. But brushing against that surface yields a very fine "dust" of what I assume to be tiny polystyrene particles. [That's not frightening in itself, but might be prevented with a light coat of acrylic paint on potentially sun-exposed surfaces.]

SUMMARY: There is still a lot of room for refinement and innovation in kiln design and construction.

Bob

 

[Moth]

Thinking about a box for the kiln. Either a small ex commercial fridge (something that's stainless steel on the inside), rather than making one.

Either way, I'll need to spend some money on something. Then I realised I won't have much leaf (30 odd plants crammed in 5gal pots) and I won't need much space to ferment them, as per:

For fermentation, I now cram well-cased whole leaf into ~24" x 36", heavy-duty, clear plastic bags [tops left OPEN], which I then either stack on the wire shelves or suspend with clothespins from the bottom of the shelving.

This made me consider using one of these Hot/Cool box on Amazon. Its a picnic cooler / heater (guessing a peltier thermoelectric coupler) in an insulated box. It heats to 65c/149f, so I'd need to control it with the shc2000, and set the humidity somehow...

Thoughts?

 

[Jitterbugdude]

My only thought would be... is it going to be big enough? When I made my very first kiln about 20 years ago it was a box approximately 2 ft x 2 ft. When I started growing 200 plants per season I made a 4x4x5 ft box but now that I have a very large supply in storage I am back to a small kiln that I use for my container method (mason jars). So ask yourself, is it big enough? Are you going to expand your grow each year? If so, you will have to spend more money for a bigger kiln.

Also, That hot/cool box runs on 12v. Do you have a battery or solar powered system that will allow you to run it for approximately 4 weeks?

 

[Moth]

It runs on both 12v and 240v, although, it its a bit small. On reflection, I'm sure its probably not intended for the heating mode to be on for 6 weeks...
Even if it could handle it, I'm unsure I'd bet my house on it (thinking fire hazard)
Pity

 

[ChinaVoodoo]

I am a temperature and humidity controller guy. I supply heat indirectly and add air circulation simultaneously.

A heat lamp of any kind will overheat one area and leave cold spots. So I use cheap light bulbs inside a steel box or pipe so that no direct light/heat comes out of the box/pipe. An in line fan blows air through said box/pipe, instantly spreading the heat evenly through the kiln or curing chamber via blowing hot air.

Benefits include very tight temperature control because the light bulbs with constant air flow around them heat up and cool down very rapidly.

It is also very efficient. 100w will easily heat an insulated and sealed 50 cubic foot box to fermentation temperatures while only being on 25% of the time.

Down side is that bulbs can burn out so it is better to run several. For example, three 40w bulbs. Two will be enough, and since there is a digital controller, three is not too much.

Other downsides are cost, and it can be cataclysmic when the controller fails, especially if it fails in the on position which it did for me once when I was growing seedlings which got cooked.

 

[ChinaVoodoo]

I still use humidity controllers for curing, but for fermentation I have switched to no humidifier at all, and packing the tobacco into sealed buckets which don't let moisture escape.

 

[deluxestogie]

In the US, at least, small incandescent bulbs are becoming harder to find.

Bob

 

[GreenDragon]

How about large cardboard box(s) with a heating pad? Cardboard is a great insulator and pretty much free nowadays if you do any internet shopping. And heating pads have a built in controller.

 

[ChinaVoodoo]

How about large cardboard box(s) with a heating pad? Cardboard is a great insulator and pretty much free nowadays if you do any internet shopping. And heating pads have a built in controller.

I can't imagine how the heat could be evenly distributed, but with the right amount of air flow, I think it could work.

 

[ChinaVoodoo]

In the US, at least, small incandescent bulbs are becoming harder to find.

Bob

What about halogen bulbs and the ones that go into the oven?

 

[deluxestogie]

They're out there, but I have to go out of my way to find them.

Bob

 

[Moth]

In the US, at least, small incandescent bulbs are becoming harder to find.

Same in the UK, although, the trend seems to be a halogen bulb fitted in place of the incandescent bulb filament, in a traditional bulb. Which is a pity, I'd hoped LED bulbs would be the direct replacement from a environmental perspective. Globally, if we all swapped it would save a lot of power (halogen running costs are 80% of incandescents, LEDs are 10%)

What about halogen bulbs and the ones that go into the oven?

Now that is an inspired idea - amazing heat tolerance, small, tough....

 

[ChinaVoodoo]

It depends on where you live and what you heat your home with and for how long.

If the waste energy from your lightbulb is used for another purpose, ie. Heating your home, it becomes effectively 100% efficient. (20% light, 80% heat.)

A study was done in Newfoundland that showed switching to fluorescent bulbs resulted in increased heating costs and pollution.

 

[stic]

Thinking about a box for the kiln. Either a small ex commercial fridge (something that's stainless steel on the inside), rather than making one.

I purchased an ex blood bank stainless fridge (insulated front glass door, stainless racks and trays) 2nd hand for $2NZ...

It's 7 feet tall, with an internal capacity of approx 5 feet, by 3 feet by 3 feet...

 

[MrMotion]

I'm going to revive this thread an ask what humidity every likes to have in their kiln during the 4-6 weeks of kilning?

I'm actually headed this week to pick up supplies for building it. I've already got an Arduino, and I have some basic programming experience. I'm going to purchase relays to control the 2QT crock pot that my wife gave to me (missing a leg and its chipped on the rim but works great still). Still need some fans. The kiln will be in a garage (same place I'm going to air cure the tobacco).