Some guidance on the current humidor concepts. Following our disquisition on table humidors, in this edition we address the concept of the cabinet humidor.
A very popular and widespread variety is the small cabinet with three to seven drawers. Unfortunately these are, with very few exceptions, not suitable for maintaining an even humidification. The drawers are usually as deep as the humidor itself, and have only a few elongated holes in the base, which are completely covered by the cigars.
This method of construction does not allow the air to circulate. In order to humidify a humidor of this type you would need to place a stick shaped humidifier in every drawer.
If you think such errors in construction are to be found only in cheap humidors imported from Asia, then you are mistaken, as demonstrated by this beautiful Swiss humidor.
If you open the doors, you will see that the drawers are touching each other, with no spaces between them, and with only three small holes in the base of each.
The humidification system covers the whole base, and sits directly under the first drawer, with the result that the cigars in the bottom drawer are so wet you could wring them out, whilst the cigars in the top drawer are so dry they crackle. An object made in this way is fine for storing jewellery, but not for cigars.
Ways of improving drawer humidors
If you are contemplating buying a drawer cabinet, ensure that there is as much space as possible between the drawer and the back wall. This allows the humidified air to enter the individual drawers from behind. An alternative solution is to remove the drawers in the lower part of the humidor, thus enabling the humidor to be fitted with a humidifier on the back wall. Only in the upper drawers will you then need to supplement this with a small humidifier. This procedure can lead to a completely satisfactory result.
A particular kind of small cabinet is the humidor with hinged lid. In addition to a tray for around 50 to 80 single cigars in the top, it also provides storage space for up to 12 boxes. The large uninterrupted volume of air can be evenly humidified and the humidity is able to rise easily through the holes in the base of the tray.
Large volume cabinet humidors
No matter how big your humidor, it will always be too small. The forward thinking passionado plans ahead, and will buy himself a cabinet, meaning a piece of furniture that stands on the floor, right from the start. We want to pay particular attention to this, since significant sums are at stake here.
The real problem with such models is that they often include inappropriate materials and the cabinets are often constructed in a manner that prevents the air from circulating.
The shelf bases are usually made of medium-density fibreboard (MDF), a mixture of wood and plastic dust which has been combined under pressure with glues such as urea-formaldehyd or phenol-formaldehyde.
The top and bottom surfaces of the panels are covered with a cedar veneer and a few elongated holes are then cut out to allow for “air circulation”. And there you have it – a catastrophically badly made shelf base is finished. The untreated MDF is visible on the outer edges and in the surfaces of the air holes. This material already smells unpleasant when it is dry, but if it is exposed to higher levels of humidity, then the formaldehyde starts to escape into the air, causing a musty, mouldy smell, which, naturally, is taken up by the cigars.
Humidification using plastic containers with sponges is entirely unsuitable! From a purely physical point of view, this kind of passive humidification by evaporation simply cannot work for such a large space. Furthermore, a relative humidity of over 90 per cent near to the sponge causes the MDF to swell and the boxes inevitably begin to go mouldy. Even if you remove this form of humidifier and replace it with an electronically regulated humidification system, some problems will still remain, for example, solid drawer bases that extend from the front edge to the back wall of the humidor, cigar boxes that completely cover the air holes, etc. If you possess such a cabinet, then a radical course of action is necessary to get sensible results: completely remove all inner furnishings; clad any remaining MDF surfaces with Spanish cedar or mahogany; install solid wooden slat-style shelves which are constructed in such a way as to allow air circulation; and install a humidifier pointing upwards on the back wall in the bottom portion of the humidor. Cigar boxes should then be stored flush with the front of the cabinet, so that the back is kept free for air circulation.
In better constructed examples, the drawer bases are not made of raw MDF, but at least of plywood (cross grained glued layers of veneer) However, this too is not usually waterproof, which can result in mould forming on the underside when exposed to high levels of humidity for a prolonged period.
Another example of poor construction is the combination of shelf and tray. Usually longitudinal elongated air holes have been cut out of the shelf base to allow for better air circulation (usually far too narrow, but let’s say it is the thought that counts), and then a tray is placed onto this, with transverse elongated holes cut out of its base. The result is that the slits in the shelf are covered by the solid parts of the tray.
Correct humidification of a cabinet humidor
Since it is completely out of the question to humidify a cabinet of a volume greater than 80 litres (the size of a small fridge) using passive humidification we will say no more on this subject and will only discuss active humidifiers. When selecting an electronic humidifier the following basic requirements should be observed
- A dedicated air guidance system for targeted airflow in the humidor.
- An extremely fast reacting, long-term stable sensor.
- High humidification performance, so that the target humidity level can be restored as quickly as possible after the humidor has been opened.
- Integrated air circulation function (without humidification).
If the humidifier is placed in the bottom of the humidor and the humid air is blown directly at the bottom of a shelf placed directly above it (and which holds boxes of cigars), then the air humidity in the bottom of the cabinet will be extremely high and will decrease steadily higher in the cabinet. The fluctuation in relative humidity can be as high as 18 per cent! Installing a commercially available room humidifier (with a dull hygrostat) is a poor solution, just combining two products that were never meant to go together. You would have to rotate the cigars in the cabinet at regular intervals, which is really not ideal. It is best when the humidifier is able to direct the air up the back wall of the humidor unhindered by cigar boxes or trays. An alternative is to install a double back wall as a dedicated air guidance system.
The Perfidy of Physics
Humid air is lighter than dry air, and consequently it rises. In that case, shouldn’t the humidity level in the top of a cabinet humidor be higher than at the bottom? That is not, in fact, the case. The humidity is always greater at the bottom than at the top.
So, can a humidor defy the laws of physics? Of course it can’t. This apparently nonsensical effect can be explained by the temperature differences in the humidor. In a humidor that is as tall as a man, the temperature at the top is approximately 1° C higher than at the bottom, and if it has lighting installed, which also warms it up, the temperature difference can be even greater.
Since warm air can hold more water than can cold air, a lower level of humidity will occur where it is warmer than where it is colder. As long as the humidifier fan is running and the air subject to convection, these differences in humidity will level off. However, once the target humidity level has been reached, if the humidor is not opened and no humidity thereby lost, no convection will occur and this results in the aforementioned gradient of humidity from top to bottom of the humidor. This can be counteracted by adding to the humidifier with a built-in circulation fan which operates at intervals, and causes a convection of the air at regular intervals irrespective of the humidity level.
A humidor must seal tightly
That is the accepted wisdom. The more tightly the humidor seals, the more constant the relative humidity. That is the unanimous opinion. In fact, precisely the opposite is true.
A good cabinet humidor is constructed in such a way that a small amount humidity is constantly escaping, either through the gaps in the doors or through deliberately in-built outlet openings in the top.
This is sensible for two reasons: firstly, this reduces the differences in temperature, and secondly it prevents over-humidification. Now, you are going to ask how is it possible to over-humidify your humidor if it is fitted with a precision humidification system? Once again, it is physics that has turned our view of how to store cigars on its head.
If the temperature in a humidor drops, the relative humidity increases. If the air warms up, you would therefore expect that the relative humidity would decrease, but it doesn’t. In fact, it does precisely the opposite – it rises. The reason for this is that the organic substances in the humidor (wood, cigars) store water. If the temperature rises, the binding energy between molecules is reduced, and the water in the organic substances increasingly begins to evaporate. This causes the increase in relative humidity in the humidor even when the temperature is rising.
In practice, this means: you should reduce the relative humidity in your humidor to around 68% at warm times of year. Thus, if the temperature in the humidor rises by an average of 3–5°C during the summer, the water evaporating from the wood and cigars will increase the humidity in the humidor.
If the humidity level was lowered in advance to around 68% rh, this will result in a humidity level of around 72% rh. If you do not reduce the humidity in advance, then the level will rise to around 76–78% rh.
There are, of course, are a few other criteria which are of importance when seeking out a good cabinet humidor – but we have covered the most important here, and you are now in a position to separate the wheat from the chaff.
This article was published in the Cigar Journal Summer Edition 2012. Read more