John Rolfe, the first Englishman to grow and cure tobacco, obtained a dark, rough product that nobody would buy today, but at that time it was appreciated almost as much as the Spanish variety. Matoaka, Powhatan’s daughter, had taught him how to air-cure the tobacco leaves and he later refined the technique, although in those days the leaves were not hung in ventilated hinged-board barns, but placed beneath a simple shelter. In other parts of America the tobacco leaves were cured by wrapping them up in ferns, or burying them under layers of straw, or else they were smoked, or left partially to dry out in the sun. However, air-curing was the most popular technique for a long time, although when excessive humidity in the air threatened to ruin the whole crop, fires were lit to dry out the air. In this way, what was initially an exceptional use of artificial heat, soon proved to be an alternative technique that found favour, imitating or reinventing the smoking methods that had been introduced by the Muskogee Indians.
Thus, the third technique results in fire-cured tobacco. This involves controlled, slow-burning open fires, not directly in contact with the leaves that are almost dry. One way was to light large log fires outside and then bring the hot coals inside the barn, or else bark and damp wood was used. This process was still preceded by a period when the leaves were left to wilt in the shade and then dried in the sun. Up to the late nineteenth century the coals were placed in ditches in the beaten earth floor and covered with flat rocks, and later with flat sheets of metal. Although it was not prudent to hang the bundles of leaves directly above the fires, in fact this was the best way as the tobacco would dry more effectively in contact with the hot fumes, which would then disperse through the windows, or chimneys. The fires were not constantly lit, and their intensity depended on the stage of the curing process. Indeed, the highest temperature was needed in the final stage, in order to dry out the stems of the leaves.
It is worth mentioning two things after this brief description of a process using direct fire, whose numerous variations were and still are trade secrets. The first is that the high temperature used for the last part of the process was often a potential fire hazard, despite all the precautions taken. The second was that a smouldering wood fire emitted a great deal of smoke, which in turn would penetrate the pores and smoke the leaves, and thus the leaf acquired the flavour of whichever wood was used (in addition to the aroma of the variety of tobacco grown). Nowadays, direct-fire curing is only adopted in the case of tobacco varieties that are enhanced by this process and the type of aromatic wood is carefully selected. In the early nineteenth century there were two factors that boosted this process: the growing popularity of a “smoky” flavour and the need to speed up and better control the whole process. However, for some important tobacco strains smoking was not really the answer, so there remained the problem of how to speed up the process and control it effectively without recourse to this technique. A solution was eventually found, and by the end of the century another method had taken over, although the direct-fire method was still in use.
The fire-cured technique may vary in its duration, lasting from a few weeks to a few months, including the preliminary stages without fire. The tobacco obtained through this process is low in sugar but high in nicotine, and the smoke blocks the pores in the leaves, thus preventing any further addition of aromas. Nevertheless, for this highly characteristic variety of tobacco that is certainly not a problem. Nowadays, in various parts of the world, from America to Asia, certain strains of strong tobacco are cured in this way (such as the well-known Latakia and Kentucky blends) which are used for pipes, as well as for cigarettes, snuff, chewing plugs and special cigars.
In the past tobacco growing involved employing large amounts of labour, and thus in the Southern States of America African slaves were imported to grow and harvest tobacco. The first generation arrived in Jamestown in 1619. Two hundred and twenty years later, legend has it that a slave by the name of Stephen Slade worked for a tobacco farmer in Caswell County (North Carolina), of the same surname. In fact, it was the owner, Abisha Slade, who imposed his surname on the slave, who had the taxing task of overseeing the curing (direct fire) of Abisha’s tobacco, as well as operating the blacksmith’s forge nearby. One night in 1839 Stephen awoke with a start: he had fallen asleep and so the fire was going out, which would damage the leaves. In a dramatic attempt to save the leaves Stephen rushed out to the forge, got hold of some charred logs and ran back to the barn and threw the logs onto the dying embers in an attempt to revive the fire. The fire certainly flared up again, perhaps too much. Indeed, the sudden burst of heat and resulting rapid dehydration turned the green tobacco a bright yellow. What would his master have said? But Abisha Slade sold that particular tobacco for an extremely good price. Not only that, but he rewarded Stephen and then set about studying the reasons behind this phenomenon with his brothers. By 1856 he had finally refined the technique to obtain bright yellow tobacco constantly from plants grown in sandy soil, which had been known before, but before Abisha’s discovery the tobacco only turned yellow sporadically and quite by chance.
Abisha and his brothers were not the only ones to undertake research into the techniques, as they lived in a period in which there was an outpouring of theory, experimentation and inventive activity that resulted in the growth of industry. The accidental use of charred wood in tobacco curing by Stephen had in fact already been practiced from Virginia to Ohio in the early nineteenth century, as this type of wood produced little or no smoke and so was useful for those types of tobacco that were not appropriate for the smoking method. However, from the 1820s onwards some farmers strove to develop a technique which included all the advantages of fire-curing, while at the same time removing the disadvantages and constraints of using smoke, regardless of the type of wood used.
From the 1820s onwards, in fact, some of the buildings in the USA used for tobacco curing, the tobacco barns, were altered. The fires were removed from the floor and moved externally or to the cellar. The heat travelled from the furnace through metal tubes (“flues”) to the interior of the barns, uniformly drying the leaves hung onto poles, and then dispersed. In this way the leaves were no longer directly exposed to smoke, and thus it was now possible to cure any variety of tobacco using any type of fuel. A further benefit from adopting this new technique was that fire hazard through direct fires was largely reduced and at the same time it was far easier to control the temperature throughout the whole process and it was also more accurate.
As we said earlier, it was the 1820s. Why did flue-curing take so long to catch on? On the one hand farmers who had used direct fires all their lives were reluctant to change, and on the other the introduction of charcoal in fire curing had made this technique more interesting and thus was used widely. There was also the fact that it was costly to install flues in the barns. However, the greatest difficulty for these farmers was to adapt to the new methods and abandon the secret techniques that had been handed down from generation to generation. Meanwhile, an ever-growing number of farmers and later scholars sought to understand more fully the process which would determine the best conditions for curing. In the 1870s an extremely important advance was made by Robert L. Ragland, a tobacco planter, when he identified the different stages in the process and determined that each stage had a particular temperature and humidity. As these theories gradually spread and the new techniques proved to be successful, the mentality changed and the techniques started to be adopted more rapidly. It was realized that it was essential to monitor the conditions at each stage of the process and that as a result flue-curing was by far the best technique. The technique swiftly spread after that, but as late as 1919 there were still only a third of the tobacco barns that had been converted to flue-curing. In the mid-1930s this rose to 48%, and reached 61% by 1978. Hence, the tobacco industry is closely linked to flue-curing and its further developments.
Thus, the fourth method is indirect-fire curing which results in flue-cured tobacco.
The difference between this and direct-fire curing is the use of tubes which protect the leaves from direct smoke. The whole process lasts much less time, about a week, and in terms of cost this is advantageous. The controlled temperature is raised during each stage and at the same time the humidity is monitored, and the barn is ventilated when necessary. The process may vary according to certain tobacco types, as well as the rest period between one stage and the next. This is certainly the most artificial of the four techniques, allowing most control over the process, and as such is highly suited to curing Bright Yellow tobacco, which is initially cured using direct fire and charcoal, but is considered today as flue-cured. Nevertheless, its colour is not its only distinguishing feature, however appealing. In fact, the type of process, temperature and relative humidity schedule leads to a reduction of the starch level and an increase in sugar concentration and relative acidity which has a positive impact on the quality of the smoke, as the aroma is intensified and the harsh flavour is removed. As regards the nicotine content, this is generally reduced. Moreover, as the pores in the leaves are not blocked by direct smoke, further aromas may be added if desired. Indirect-fire curing produces classic tobacco for cigarettes, but it is also the most common base tobacco used for pipe blends, and one of the most well-known is Virginia tobacco.
By the 1950s another technique, bulk curing, had been developed, although it would be more correct to say that this was an evolution of flue-curing. As time went by it was increasingly difficult to cope with rising tobacco production using the same amount of labour. The process had to be reconsidered to become more efficient, in particular as to how the tobacco was arranged in the barn during the process, and thus experimentation was undertaken in this field. The first pilot bulk-curing barn was introduced in 1958, by 1960 this was marketed and by the 1980s most tobacco manufacturers in the USA had converted to this method.
The technique involves the use of much smaller metallic structures than the traditional barns, in which the tobacco is packed tight together on modular racks. The heated air under pressure is recirculated around the tobacco leaves, thus reducing heat loss and saving a great deal of energy. Temperature and humidity sensors inside these structures are linked to a computer that monitors the environment constantly. Thus, the romantic image of the old barn and its hot, humid interior full of expert workers is a thing of the past, compared to today’s more anonymous, semi-automatic process, and mechanization also extends to the racks being fed directly by the machines that harvest the leaves. Curing lasts about a week, more or less as before and the quality of the tobacco is decidedly superior. Nothing has changed for the consumer, however, as even now the process is still referred to as “flue-curing”, and the tobacco is still “Bright Yellow” from Virginia. Originally developed in America, indirect-fire curing, first flue and then bulk curing has been adopted in various parts of the world, while in America the traditional, abandoned tobacco barns have become part of the country’s heritage to be preserved.
Now that we have finished discussing the four main methods of tobacco curing, we can go back to where we had left off in the second part: raw tobacco, ready for its subsequent stages of treatment.