Cigar Preservation According to Science: Studies, Data, and Sources
Optimal cigar storage relies on precise physicochemical and biological parameters, documented by over a century of entomological research and tobacco science. What the oral tradition of aficionados expresses intuitively—the famous "70/70 rule"—is actually based on measurable mechanisms: tobacco equilibrium hygrometry, biological cycle of Lasioderma serricorne, evaporation kinetics of essential oils. This article synthesizes the available scientific data on cigar storage.
We will examine three areas documented by scientific literature: the hygroscopic equilibrium of tobacco according to the GAB (Guggenheim-Anderson-de Boer) model, the biological cycle of Lasioderma serricorne (cigarette beetle) and the critical thermal thresholds established by studies from Purdue University and Japan Tobacco Inc., and finally the hygroscopic properties of Spanish cedar (Cedrela odorata) used in humidors. Each assertion is referenced at the end of the article.
1. Tobacco Hygroscopic Equilibrium: The GAB Model
Tobacco is a hygroscopic material—it absorbs and releases moisture from ambient air until it reaches an equilibrium called Equilibrium Moisture Content (EMC). This phenomenon is described by the Guggenheim-Anderson-de Boer mathematical model, widely used in materials science.
| Relative Humidity | Tobacco Moisture Content (EMC) | Storage Condition |
| 50 % RH | ~12 % | Dry — brittle wrapper |
| 60 % RH | ~15 % | Low limit — oil evaporation |
| 65 % RH | ~17 % | Optimal low — clean burn |
| 70 % RH | ~20 % | Optimal — documented aromatic peak |
| 75 % RH | ~24 % | High limit — mold risk |
Sensory analyses conducted in the tobacco sector indicate that the overall aromatic score of cigars reaches its maximum around 70% RH, and that the 65-70% RH window constitutes the optimal compromise between aromatic development and ease of combustion [1]. Below 60% RH, the essential oils present in the leaves gradually evaporate, permanently altering the aromatic profile.
Scientific precision: relative humidity is not independent of temperature. According to the GAB model, a 1 °C increase requires an approximate 4% increase in RH to maintain the same tobacco moisture content. This is why simultaneous monitoring of temperature (thermometer) and humidity (hygrometer) is essential for rigorous storage.
2. Lasioderma serricorne: What Entomology Has Established
The main biological pest of stored tobacco is the beetle Lasioderma serricorne (Fabricius, 1792), commonly known as the "cigarette beetle." Its biological cycle and thermal sensitivity have been extensively studied—critical thresholds are now well-documented.
✅ Guizhou University study (2021): measurable growth from 21 °C
✅ Maximum reproduction at 30-33 °C — critical heatwave period
✅ Purdue study (2013): flight initiation from 22.5 °C
❌ Below 18 °C: reproductive cycle blocked (Japan Tobacco Inc.)
✅ Alternative: -20 °C for 24 h (standard logistics protocol)
✅ Method validated by Japan Tobacco Inc. (Fields et al., 2010)
✅ Effective on eggs, larvae, pupae, and adults
❌ Slow thawing mandatory to avoid condensation
✅ Direct practical implication: maintaining humidor below 21 °C prevents adult dispersion
✅ Ikenaga study (Japan Tobacco Inc., 2006): reproductive cycle is blocked below 18 °C
✅ Combined recommendation: stable temperature 18-21 °C = biological safety
❌ Heatwave at 30 °C+: accelerated reproduction, risk of infestation in a few weeks
Practical application: studies converge on a safe thermal range of 18-21 °C. Below this: reproductive cycle blocked. Above 22 °C: flight capability activated. Above 26 °C: accelerated reproduction. Above 30 °C: optimal conditions for the species, maximum risk. A heatwave therefore constitutes the period of highest biological risk for a cigar collection.
3. Properties of Spanish Cedar (Cedrela odorata)
The Spanish cedar used in traditional humidors is not an arbitrary choice—its physicochemical properties have been empirically selected and then scientifically validated. Three characteristics justify its use.
✅ Buffering effect that smooths micro-variations in internal RH
✅ Porous structure with dead cells = large exchange surface
✅ Effectively complements the active humidifier
❌ Requires initial "seasoning" (24-48h) for saturation
✅ Slow migration to tobacco leaf during aging
✅ Enriches aromatic profile — documented woody notes
✅ Cumulative effect observed on aged cigars (2 years and more)
❌ Gradually diminishes (10-15 years) — possible wood replacement
✅ Hori (2003): essential oils tested against L. serricorne
✅ Preventive effect — not a curative treatment against infestation
✅ Combines with thermal control for optimal protection
❌ Partial effectiveness — does not exempt from vigilance
✅ Respects the original aromatic profile of the cigar
✅ Subtle enhancement, not transformation
✅ This is why resinous woods (pine, fir) are prohibited in humidors
❌ Always check for "untreated Spanish cedar"
4. Summary: Conservation Parameters Validated by Literature
By combining data from the three preceding axes (hygrometry, entomology, cedar physicochemical properties), scientific and industrial literature converges on a set of consistent parameters for optimal cigar conservation.
| Parameter | Target Value | Scientific Justification |
| Relative Humidity | 65-70% RH | Tobacco EMC 17-20%, low mold threshold |
| Temperature | 18-21 °C | Lasioderma reproduction blockage, EMC stability |
| Inner Lining | Spanish Cedar (Cedrela odorata) | Hygroscopicity, terpenes, partial repulsion |
| Acceptable Variation | ±3% RH, ±2 °C | Tobacco sensitivity to fluctuations |
| Anti-Lasioderma Treatment | -20 °C for 24 h | Validated industrial protocol (Fields et al., 2010) |
Operational Recommendation: for most enthusiasts, the window of 65-70% RH at 18-21 °C represents the optimal compromise between aromatic development, ease of combustion, and biological safety. The threshold of 70% RH at 21 °C—the famous "70/70 rule" (translated into Celsius)—does indeed correspond to the documented aromatic maximum, but carries a slightly increased risk compared to 65-68% RH. The choice is a personal preference informed by the data.
Limits and Uncertainties of Available Literature
The available scientific literature presents several methodological limitations that should be mentioned for intellectual honesty.
✅ Finished cigars exhibit slightly different dynamics
✅ Effect of the wrapper (outer leaf) is not quantitatively well-documented
✅ Industrial studies remain the best available reference
❌ Most data comes from research on cigarettes or raw tobacco
✅ Mae Jo Thailand study (2026): documented seasonal effects
✅ Active research — regular new publications
✅ Stable scientific consensus on essential parameters
❌ Laboratory strains sometimes less tolerant than wild strains
Equip yourself according to validated parameters
Atelier Atypique offers Spanish cedar humidors, calibrated digital hygrometers, and humidifiers to maintain scientifically recommended storage conditions.
See cigar humidors →Sources and Scientific References
Bibliography
- Guggenheim, E.A. — Anderson, R.B. — de Boer, J.H. GAB model of moisture adsorption applied to tobacco. Reference mathematical model in hygroscopic materials science.
- Howe, R.W. (1957). A laboratory study of the cigarette beetle, Lasioderma serricorne (F.) with a critical review of the literature on its biology and behaviour. Bulletin of Entomological Research, 48, 9-56.
- Ikenaga, H. et al. (2006). Low-temperature as an alternative to fumigation to disinfest stored tobacco of the cigarette beetle, Lasioderma serricorne (F.). Applied Entomology and Zoology, 41(1), 87-91. Link
- Wakefield, M.E. et al. (2013). Influence of temperature, gender, age, and mating status on cigarette beetle (Lasioderma serricorne) flight initiation. Journal of Stored Products Research, Purdue University. Link
- Fields, P.G. et al. (2010). The effect of sub-zero temperatures on different lifestages of Lasioderma serricorne and Ephestia elutella. Journal of Stored Products Research. Link
- Determining the Effect of Temperature on the Growth and Reproduction of Lasioderma serricorne Using Two-Sex Life Table Analysis (2021). Insects Journal, Guizhou Provincial Key Laboratory. PubMed Link
- Effects of tobacco varieties and seasons on the life history of the cigarette beetle Lasioderma serricorne (2026). Journal of Stored Products Research, Mae Jo Tobacco Experiment Station, Thailand. Link
- Hori, M. (2003). Repellency of essential oils against the cigarette beetle Lasioderma serricorne. Applied Entomology and Zoology, 38, 467-473.
- Habanos S.A. — Official storage recommendations: 65-70% RH at 16-18 °C. Industrial standard used by the producer of Cuban cigars.
- Boveda Inc. — Technical documentation on cigar humidity equilibrium. Link
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Frequently Asked Questions
What does science say about the ideal humidity for cigar storage?
Convergent studies indicate an optimal window between 65% and 70% relative humidity, corresponding to a tobacco moisture content (EMC) of 17% to 20%. According to the GAB (Guggenheim-Anderson-de Boer) model applied to tobacco, below 60% RH, essential oils evaporate rapidly; above 75% RH, the risk of fungal development becomes significant. Habanos S.A., producer of Cuban cigars, officially recommends 65-70% RH at 16-18 °C for aging.
What is Lasioderma serricorne and why does temperature matter?
Lasioderma serricorne (Fabricius, 1792) is the main biological pest of stored tobacco. Entomological studies by Purdue University (Wakefield et al., 2013, published in the Journal of Stored Products Research) show that the insect only initiates flight above 22.5 °C. Ikenaga (Japan Tobacco Inc., 2006) showed that its reproductive cycle is blocked below 18 °C. Optimal development occurs at 30 °C, which explains why heatwaves represent the highest biological risk period for cigars.
How to treat cigars suspected of Lasioderma infestation?
The scientifically validated protocol (Fields et al., 2010) consists of exposure to -20 °C for 24 hours in an airtight container. This method is effective on all biological stages: eggs, larvae, pupae, and adults. Slow thawing (24 hours in the refrigerator then 24 hours at room temperature) is mandatory to avoid condensation that would alter the cigars. Industrial alternative: -18 °C for 24 hours or -25 °C for 4 hours, protocols validated by Japan Tobacco Inc.
Why is Spanish cedar used in humidors and not other wood?
Cedrela odorata exhibits three documented physicochemical properties: modulated hygroscopicity (buffering effect on internal humidity), emission of aromatic terpenes (α-cadinol, cadinenes) that enrich the tobacco's bouquet during aging, and partial repellent activity against Lasioderma serricorne documented by Hori (2003). Unlike oak or softwoods, cedar does not impart strong secondary aromas that would mask the tobacco's profile — hence its dominant position for over a century in humidification.
Is the "70/70 rule" scientifically founded?
Partially. The traditional "70 °F and 70% RH" rule (approximately 21 °C and 70% RH) corresponds to the aromatic maximum observed during sensory analyses — the overall aromatic score of tobacco indeed peaks around 70% RH. However, this maximum value comes with a marginally increased risk of fungal development and biological activation of Lasioderma (whose flight threshold is 22.5 °C). Modern producers (Habanos S.A., Boveda) now recommend 65-70% RH at 18 °C, considered a better compromise between aromatic development and biological safety.
How to apply these scientific principles in daily practice?
In practice, four parameters to monitor. One: maintain the humidor between 65% and 70% RH (ideally 68%) with a regularly calibrated digital hygrometer. Two: maintain the temperature between 18 °C and 21 °C — a wine cellar can be used if necessary during heatwaves. Three: exclusively use a humidor lined with untreated Spanish cedar (Cedrela odorata). Four: in case of suspected Lasioderma infestation (small, clean holes on the cigars, brown dust in the humidor), apply the -20 °C protocol for 24 hours in an airtight bag. These four actions cover the essentials of what scientific literature establishes as optimal storage conditions.
