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Wet Bulb Calculator, without the Wet Bulb.

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deluxestogie

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That's an interesting and handy calculator.

The use of a wet bulb and dry bulb was the only way to measure relative humidity in the not so distant past. [It indirectly measures how rapidly the saturated wick of the wet bulb is able to evaporate water--and dissipate heat from that thermometer--given how much moisture is already in the ambient air.] For the 21st century, if you have a humidity gauge that is rated for the temps required, it would make more sense to just go by RH at a given temp. Unfortunately, all of the flue-curing charts that I've seen are from the pre-digital age, and use wet bulb readings.

If you've run the calculations, others might benefit if you post the values.

With my very crude flue-curing chamber, I go by color (peeking inside) for the first phase of the cure, then cast my fate to the tobacco gods for the remainder of the cycle.

Bob
 

Brown Thumb

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With the chart I used these were the values I came up with.
Yellowing @ 100 Degrees, 97 wet bulb, RH would be 95%
Wilting @ 118 Degrees, 100 wet bulb, RH would be 55%
Leaf drying @ 135 Degrees, 105 wet bulb, RH would be 38%
Stem Drying@ 165 Degrees, 110 wet bulb, RH would be 18%
 

Brown Thumb

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Thank you, Bob
They are pretty close to this schedule I used last yr. I guess they can vary a little.
image.jpg
 

deluxestogie

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Duh. I just noticed that the RH is on the right of that chart--the same one I've used as a guide. I think your numbers for RH are within the range that mere mortals can control the humidity.

Bob
 

leverhead

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Thank you, Bob
They are pretty close to this schedule I used last yr. I guess they can vary a little.
View attachment 12211

There is an error on that graph, it shows the RH in the mid 80's% for yellowing. If you check it, the proper RH for yellowing is 93-95%. If you're using the wet/dry bulb split (the dry bulb line is missing from the graph), everything works OK. If you use the indicated RH (mid 80'%) you'll get more green in the finished cure, especially for longer yellowing time.
 

Brown Thumb

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I agree with you, It took forever last year to yellow my leaf last year using the chart in the mid eightys.
I am running at 96 rh this yr. The steamer keeps it spot on.
 

deluxestogie

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Here is the same chart with the subtle gray dash line showing:

Flue Cure Chart.jpg


I don't know the source. It assumes you are starting with fully ripe leaf.

Bob
 

leverhead

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Thanks Bob! After my old computer died, I haven't gotten all of my old saved files back. This is what the chart should look like.

Flue Cure Chart corrected.jpg
 

CT Tobaccoman

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Dry bulb-wet bulb is still the tool used in Connecticut for curing shade. It is very simple. After ten days of firing, or even 5 days, what you want to see is a 14 point spread between wet and dry. Shade is fired 10 days first, then refired 5 or 6 times for a day or two each time. Couldn't be simpler.

BTW, a reading of 92 degrees dry bulb, 78 degrees wet bulb is ideal. That is the spread that you work for. Over 95 is too hot. That's what I was taught over and over--a 14 point spread.

Can't buy wet and dry thermometers anymore, but there are thousands of them in the Conn Valley left over from when there was 900% more shade grown here. I guess the mercury is too dangerous for us idiots nowadays. Isn't it great that the government takes such good care of us? We are so dumb, we might drink the mercury or something. We must do digital or not do at all. But Conn USA shade is still cured analog.
 

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There are loads of sites on the internet, where you can actually make a wet bulb thermometer - all you need is some PVC pipe, a shoe lace (for a wick), and a thermometer. I was going to do this, until I found this handy chart on an air conditioning site. If you know the RH from your hygrometer, as well as your temp, you can use the chart to give you an idea of your wet bulb temp:

wetbulb2.jpg

Copied this as a screen shot, so the numbers are a bit fuzzy, but readable.
 

deluxestogie

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The drawback of using an actual wet-bulb thermometer is that you have to be able to see it, which may mean opening the container door--which alters both the temp and the humidity. If you happen to live in the 19th century, then that's all that is available to you.

Bob
 

Bex

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The drawback of using an actual wet-bulb thermometer is that you have to be able to see it, which may mean opening the container door--which alters both the temp and the humidity.

That's why I figure having a hygrometer (with a probe) and the chart will be helpful. Knowing the RH and temp would give you an approximate indication of the wet bulb temp, without having to open anything....
 

CT Tobaccoman

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We in Conn Shade are still in the 19th century some ways. People are unwilling to use digital hygrometers, they don't trust them. They can be affected by altitude. And , as it happens, in experimentation, there was often a conflict between dry-wet bulb and digital hygrometer readings when in the same curing shed.

I can't figure out the chart above: what would a spread of 14 points between wet and dry be in terms of relative humidity? Or, does the temperature have to be known? (another drawback of the digital, if so.) How about 92 dry, 78 wet, which is the ideal shade tobacco curing condition.

I get it that you are reading humidity from outside the flue chamber. I didn't think of that at first. So, I guess you have no choice.

If I have a choice, I will always use wet-dry bulb mercury thermometers, if I can find one anymore. For fear of mercury I think they stopped selling mercury thermometers, haven't they? So glad the gummit protects us so well. Good thing Conn Valley barns conceal hundreds.
 

Bex

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The use of a wet bulb and dry bulb was the only way to measure relative humidity in the not so distant past. [It indirectly measures how rapidly the saturated wick of the wet bulb is able to evaporate water--and dissipate heat from that thermometer--given how much moisture is already in the ambient air.] For the 21st century, if you have a humidity gauge that is rated for the temps required, it would make more sense to just go by RH at a given temp.

I'm glad I found this statement. I'm having a bit with the wet bulb conversion (it apparently looks for barometric pressure as well???). As I have a hygrometer, so as long as the RH is within the proper spec, this is all I need to 'worry' about, insofar as humidity is concerned, correct?? I understand the ramifications if there is not enough humidity in the chamber, particularly while the yellowing phase is going on. But what happens if there is too much? For example, if the chart indicates 95%, and you're running 98%, etc. - is there damage done?

While 'researching' I found this:

The major problems which occur during curing are leaf browning, over colouring, sponge, runback and scorching.
Leaf browning is caused by having humidity levels too high when the temperature is increased at the end of colouring. This causes the leaf to continue to respire until all the sugars are used up, causing a reduction in weight and leaf browning.
Sponge is a term used to describe a leaf which has been too wet when the temperature has been increased at the end of colouring. Spongy leaf is typically yellow brown, thick and poor quality.
Runback is caused by moisture from the stem seeping back in the leaf blade once it has been dried. Runback occurs when the kiln is allowed to cool down during the lamina or stem drying stage.
Scorching is caused by an increase in temperature during the final drying stage above 70C. Scorching causes the leaf to become 'cherry red' in colour.


It would seem to indicate that too much humidity/moisture would cause problems once you are starting to raise the temp after yellowing is complete. So, would this mean that you must make sure that leaf moisture and/or humidity levels are within the proper boundaries before you raise the temps for wilting??
 
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