Desperate about humidity in my curing fridge!

Discussion in 'Curing' started by davidk, Oct 10, 2014.

  1. Hi,

    please could you give me some advice? I'm beginner in curing, I'm on my second fridge and I still have the same problem: humidity is most of the time >90%. Most of the discussion I found are about opposite problem – about how to humidify fridge from being too dry.

    My setup is:

    * 180cm tall big fridge (first one had cooling element inside the chamber and I thoughts that's what is causing too much humidity as it got periodically frosty and then defrosted; my second fridge has the cooling element in the fridge wall)

    * DHC-100+ humidistat (which looks identical to Willhi WH8040)

    * ATC-800+ thermostat which controls the fridge (and could control heating but not needed at this time of the year)

    * humidifier, heater, and also dehumidifier

    * computer fan I can regulate

    What I'm trying to dry cure:

    * 2kg batch of pork sausages; hog casings

    What I tried with what results:

    My first fridge:

    #1) I run dehumidifier in the fridge to keep humidity low (85 to 75%). The dehumidifer got triggered quite regularly – once/twice an hour. I tried this several times but drying time gets very rapid (40% weight loss in less than 10days) and sometimes casing harden up. My conclusion is that dehumidifier is too aggressive and this is a bad idea.

    My second fridge:

    #2) no dehumidifier; accept higher humidity; sausages gets quite “sticky” on the surface after a day and washing it off does not help as next day they are sticky again. My conclusion: this is bad too; stickiness is usually followed by mold; I thought that maybe my humidistat readings are wrong but if they really were then I would face casing hardening instead of stickiness

    #3) dehumidify the fridge down to for example 50% RH each 6 hours. After dehumidification stops I can see humidity climb up pretty steeply – five to ten minutes and it will be back on close to 90%. That does not make any sense to me - where is the humidity coming from? the fridge is quite big and amount of sausages is quite small.

    Please, any ideas??? I'm in need of some. Am I doing some beginners mistake?


  2. I think the fridge is the problem. I just checked it few minutes after its cooling cycle I can see lots of condensation inside on the back wall. Wiping it dry makes it reapprear after next cycle.

    Beginners instructions for dry curing making it sounds like any fridge will do but I do not think so. :) Or maybe I just had a bud luck with my ones. They were both secondhand, several years old.

    Any advice on what to look for to get the right fridge next time?


  3. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    When your fridge defrosts, the liquid is supposed to drain down near the compressor to evaporate into the room.... Maybe the drain is pugged and you are recycling the water.... Check the drain tube... they sometimes plug with mold.... Find it under the fridge and back flush it with a syringe or turkey baster, or shoot air up the tube from a compressed air can you clean your computer with... or find the drain tray under the cooling coils and see if the water drains.....
  4. Thanks. I checked that and the drain is OK.

  5. I've just ordered a new humidistat. I'm suspecting the current one might be faulty. Fingers crossed that will be answer to all my problems! I will keep you posted.

  6. dcarch

    dcarch Smoking Fanatic

    If the refrigerator's compressor is too powerful, it cools down the temperature too quickly, there is not enough time to extract the humidity.

    That is what every air conditioning expert will tell you.

    What kind of refrigerator do you have?

    Last edited: Oct 12, 2014
  7. What's the temperature of your curing chamber?
    How many times a day are you opening the door?

  8. "Siemens Vinotheque", >8 years old, 190cm tall, supposed to fit 72 bottles of wine.

    What you say makes lots of sense to me. I have the fridge in garage where ambient temperature these days is around 12-18C and so my cooling cycle (to keep the fridge at 15C) is often very short and infrequent. So are you saying I need to place the fridge into sun :) or wait till Summer so that I get regular and longer cooling cycles which will bring the humidity down? That sounds logical to me. Not pleasing, but logical. :)



  9. So it's relatively small.
    The humidifier oversaturating the chamber is another thing to consider.

  10. dcarch

    dcarch Smoking Fanatic

    You may try a little light bulb inside, 50-watt, if it helps go 100-watt. Let the compressor work 80% of the time. Once the food is dried, then you don't need the light anymore.

  11. Aiming for 15C. Door once/twice a day. There where times when I tried to minimize door openings and see if some equlibrium develops in the fridge. But it never did apart from RH going to HH (>99).

    I will double check it when my humidistat replacement arrives and see. I did few tests yesterday with the empty fridge (I had to dump the sausages away as they were not going anywere positive) and even with empty dry fridge which I dehumidified to for exaple 50% I could see that humidity climbed back to over 90% in hour or so (with fridge being completely empty!) I also noticed that WH8040 humidistat which most of you guys seems to be using has also temperature probe but my DHC-100+ does not. So hoping to get better results/accuracy with the new one.


  12. That's a good trick to try!


  13. starwars1138

    starwars1138 Fire Starter

    Hey David - I found this blogto be pretty helpful with regards to smaller fridges and their tendency to stay TOO humid.

    This one is more directed at maintaining humidity which isn't your problem - Link removed

    This one deals with smaller fridges:  Link removed

    If you are concerned with having a light source in the chamber there is this idea: Link removed

    It looks as though you are heading in the right direction.  This guy here discusses the problems with the small fridge and hanging a desiccant on the back wall too:  Link removed

    Anyway - keep us posted.

    UPDATE:  I was informed that off-site links are not allowed per the forum rules.  As such, I've removed them.  Sorry for the rule violation!
    Last edited: Oct 16, 2014
  14. starwars1138, thanks very much for the links! Very useful.

    The guy in the youtube video had an alternative solution which I found quite interesting too:
    1. placing a bag of desiccant into the fridge; and
    2. making a hole in the fridge door and inserting a computer fan into it and controling the fan via humidistat - when humidity is too high start the fan to bring inside air with lower RH from outside
    Desiccant/silica gel sounds like a good idea depending on how long they can last and how they perform. I may try that. 1kg of silica gel does not look that expensive.

    Fan could work quite well too. Especially outside of Summer time. Hmmmm....something to think about.

    I really appreciate all your comments/suggestions! They made me pretty hopeful again. I've got a dimmer and a light socket today and will try to put them in place later this week and see what difference is makes!

    Thank you all once again, I will keep you posted on my progress.

  15. dcarch

    dcarch Smoking Fanatic

    Desiccant can be expensive and may not have enough ability to absorb large quantity of water.

    Don't need to make a hole in the door for the fan. The door gasket is very flexible to allow the wire to go thru.

    Try this:

    Mix a small quantity of dishwasher detergent solution. Wipe the solution on the cold walls of the refrigerator. Moisture condensed on the cold walls should sheet (not bead) and cascade down the walls. If this works, find a place on the inside bottom of the refrigerator and drill a small drain hole to drain away the water. Be careful not to damage any operating components.

    You may need to wipe the solution every few hours.

    Last edited: Oct 16, 2014
  16. If you use silica gel desiccant, be sure to use the type that's approved for use around food (uncolored)...the color indicating type has nasty stuff (cobalt chloride which is a considered a class 2b carcinogen) in it that sholdn't be used near food.

    I use 500g. (about $13.50 including the shipping) added by a fan.

    It's capable of absorbing 20% of it's weight (100g) in water.

  17. I just finished a modification I'm quite hopeful about! I returned back to my first older fridge which has the cooling element exposed in the top half.

    As you can see from the picture I decided to isolate the cooling element using unused underfloor insulation (polystyrene). I made two holes in the insulation into which I put two computer fans - one pushes air in and the other one out. And they are both connected to the same circuit as fridge itself. The result I'm hoping to achieve is that whenever fridge is cooling the fans will be on too. And they will be moving air between these two spaces I just created. And as the air full of mostuire from the fridge chamber is passing the cooling element the moisture should condense on the cooling element and turn into frost and only drier air should return into the main chamber.

    And the defrosting happens (mostly) on the insulated side where the drain is located too. In theory this could work. :)

    I also have a dimmer finished with 40W light bulb which I can use to trigger cooling (that is dehumidifing) cycle more often if needed.

    Fingers crossed! I will let it run for a day or two and later hook in the humidifier too and see how it performs.

    Last edited: Oct 19, 2014
  18. It works! Brilliant! The fridge is still empty but I have really good control of the humidity now.


    Here is a recap of what I've learned. It applies to any fridge which does not have built-in fan and is designed either with a cooling element exposed inside the fridge or hidden inside fridge's walls.

    Understanding basic physics does help! :) What I was missing to know is this: when fridge cooling element is on what happens is that molecules of water are drawn out of the air and they condense on the cooling element (only to turn into frost shortly after). This has one great benefit: air inside the fridge becomes less humid. Few minutes of cooling may result into 20% or more drop in relative humidity. That's great. Now the problem starts when fridge cooling stops. At that moment frosted water turns back into liquid water and it partially drains out of the fridge and partially vaporize back into air which in turn increases air humidity in the fridge. In my experience only negligible amount of water is drained out and most of if returns back into air in the fridge. And situation is back where we were before cooling cycle started. Well, it is worse than that. Sausages/meat hanging in the fridge are releasing its own moisture into air and that makes humidity to rise and rise.

    Knowing this gives us two ideas how to keep humidity low:
    • do not allow water to vaporize back into the fridge's air
    • keep running fridge's cooling cycle all the time
    Keep fridge cooling cycle run all the time can be easily done by adding a 40W light bulb into fridge, wired on a dimmer to further regulate its heat output, and finding a setting which triggers your fridge cycling just enough often to achieve right equilibrium between dropping and rising humidity.

    Stoping water from vaporizing back into fridge is harder to do. And pretty much depends on the design of your fridge. I was lucky that my fridge's cooling element (AND drain!) is exposed and located in the top quarter. That allowed me to isolate it and use two computer fans for air exchange during cooling phase (see the photo in my previous post). Result of that is that when fridge cooling cycle is on the air is being exchanged between these two compartments and humidity is lowered. When the target temperature is hit and cooling stops the fans are stopped too and most of the water vapor (>95%) stays in cooling compartment without impacting the dry fridge air. It defrosts there and eventually drains out. Yay!

    With fridge air dry enough it is possible now to plug in a humidistat with a humidifier and bring the humidity up to the desirable point. In my experience it means bringing it from low 50ies to 75% or 85% or whatever desired.

    We are almost there but there is still one important point to be aware of: check ambient temperature of the room where you have your fridge. Is it close to your target fridge temperature for some time of the day? My garage for example does have 15C for most of the night these days. If that's the case then what is going to happen is that fridge will stop cycling! It is simply cold enough and fridge has no need to kick in its cooling cycle. Which means that humidity inside the fridge will slowly grow and grow in time and there is nothing to bring it down. In my setup I had an old spare humidistat and so I plugged it in too and I configured it as dehumidifier and a device which I attached to it is 40W light bulb placed inside the fridge. :) What that means is that when humidity passes my higher threshold (eg. 87%) the "dehumidifier" switches on - the lightbulb goes on and produces heat inside the fridge and in few minutes it triggers the fridge to start cooling again. And as fridge cooling cycle is running the humidity drops again and the dehumidifier switches off. Pretty convoluted but works like a charm! :)

    Options I have tried and abandoned:
    • place a small dehumidifier in the fridge. It resulted in excessive drying. Caused several batches to be thrown away because of crusting. Maybe the dehumidifier was too agresive/big after all for the small fridge space? It is possible this may work perfectly well in a different setup.
    • making a hole in the fridge and bringing some drier air from the outside. This would not work in my conditions. And likely would not work in many other conditions. Relative humidity of air depends on the temperature. Taking 25C air with 60% relative humidity and cooling it to 15C will increase humidity by 20 something percent.
    • using permanently switched on light bulb to keep my fridge cycling. My energy conscience did not allow me to do that. I could do it for few hours but to create heat only to cause fridge to cool it and to run it for weeks and months in the end is, according to my conscience, unacceptable. :)
    I hope this helps other people with the same problem! I would not be able to figure this out without help from other forum members. Thank you guys.

  19. I strongly recommend using a heating source other than a light bulb.
    Light encourages rancidity in cured meats.

  20. Put your light bulb inside of an unused 1 gallon paint can and wire it up with a simple base. Google "paint can heater" and you get a ton of how to. No more light exposed to your sausages and you'll get a nice even heating source. It's what I use.

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