There is something incredibly palate-tickling and addictive about smoked food of any kind, making smoking one of the most satisfying and exciting projects you can embark on at home.
The crudest way to smoke food is simply to hang it above, or slightly to the side, of an ordinary log fire. One shouldn't ignore the possibilities of such a basic technique: it served many cultures all over the world for centuries, and in some places still does. But if you want to achieve consistent results and avoid the risk of occasionally ruining a piece of fish or meat, it will pay you to understand a little more about the principles of smoking and construct a system that allows you to generate plenty of good smoke, while retaining some control over the only other vital factor: temperature.
I have adapted the fireplace and chimney at River Cottage as the most basic kind of smoker and, while sadly it is not quite big enough for smoking a whole leg of ham, it serves me extremely well for sausages, smaller cuts of meat, and, above all, fish. The fireplace is pretty tiny, which is useful as it make it easier to regulate the heat. The fish or meat is hung directly about two and a half metres above the fire, by means of a hatch I have knocked into the chimney flue on the outside of the house. I have to climb up a ladder to put the fish in and take it out, but it's all part of the fun and I haven't fallen off yet.
If you don't have a suitable fireplace, home smokers can be adapted from all kinds of junk, such as old oil drums, metal dustbins, tall filing cabinets and even, I have heard, old fridges - although I have never quite understood that one, as every fridge I have ever had has been lined with plastic. I guess you have to strip that out!
However you set about building a smoker, there is one important principle to understand. There are essentially two ways to smoke: hot and cold. Hot smoking is effectively a way of cooking food: the temperature of the chamber is usually approaching or above 100°C, and any fish fillets or whole small fish will be cooked through in about half an hour to an hour. The presence of smoke in the chamber is simply a flavouring. The advantage, of course, is that any food cooked in this way is ready for immediate eating - and it should still be deliciously smoky. The disadvantage of hot-smoked fish is that it retains a fair amount of moisture, and is therefore not really preserved in any significant way by the process. Vacuum packed and refrigerated, it should keep for a week or two, but it is not suitable for long-term storage - unless frozen. The kind of patented box smokers you can find in fishing and camping shops are only suitable for hot smoking. They are nevertheless very handy for travelling anglers, campers and beach barbecues - hot-smoked mackerel or trout, fresh from the sea or river, are hard to beat.
Cold smoking is a more subtle procedure that requires a bit more attention to detail. It's worth it, though, as it gives you such great delicacies as the finest smoked salmon, kippers, eels, cod and haddock. The texture of cold-smoked fish is distinctly different from hot-smoked. Try cold smoking mackerel and you will see what I mean: it produces a very different animal from the ubiquitous hot-smoked version, and, in my view, an even better one. Long, slow, cold smoking is also the route to the finest smoked hams and bacon. The aim of cold smoking is to produce a chamber of smoke at a temperature of about 25-30°C. Dedicated enthusiasts of the art of cold smoking often fit temperature gauges to their smokers. I judge the temperature of my chimney by placing my hand in it where the fish are going to be hanging. It should feel pleasantly warm, but not hot - the temperature of an overheated room. Another good indicator is that if the steel bars that I have fitted to hang my fish on are too hot to touch, then the air in the chimney is too hot for cold smoking. It's time for a fiddle with the fire.
For a chimney smoker, adjusting the temperature for cold smoking is a matter of experience and a readiness to improvise. I used to simply make a fire, wait until it had burned down to hot coals, and then smother it with damp oak sawdust. This basically worked, but had a tendency to flare up if I was not vigilant, and ready to throw on more damp sawdust, or spray it with water. I have now made a shelf about 60cm above the fire on to which I can slide a stainless-steel plate. Over a small charcoal or kindling wood fire, this 'baffle-plate', as it's known technically, quickly reaches a temperature where any damp sawdust placed on it will smoulder nicely. It also has the effect of reflecting heat back into the fire, keeping the chimney above at a lower temperature. The whole system is now more stable.
Most home-built cold-smoking systems use a similar baffle-plate technique to achieve a stable temperature and a long, slow smoulder of the smoking material. Heat sources can vary from a wood or charcoal fire to a portable gas ring or even an electric element. An ingeniously simple home-made cold-smoking system I have seen uses two metal dustbins and a small portable barbecue. The top dustbin is smaller than the bottom one, which has a number of small holes drilled in the centre of its base. The smaller dustbin has the bottom completely knocked out of it (i. e. it's basically a cylinder, with a lid). The barbecue (which is less than 45cm high) goes on the ground and is lighted as if for cooking. When the coals are nicely hot, an old roasting tin scattered with damp sawdust is placed on top of the barbecue. As soon as the sawdust starts to smoulder, the larger dustbin goes on top, upside down. The smaller one, which has a couple of metal rods bolted across the top as hanging bars, goes on top - the right way up, and with the lid on. Smoke generated in the bottom bin travels up through the holes into the top bin, where the fish is hanging from the bars. A few adjustable ventilation holes in the top (i. e. bottom) of the bottom bin and the lid of the top bin help to adjust the draw of the smoke and the heat of the fire. Very simple, but it works.
Having made the important distinction between hot and cold smoking, it's only fair to add that I actually do a lot of 'rough smoking' - hanging fish above an untampered-with fire on which I am simply burning logs. It's the old-fashioned way, and a much more hit and miss affair, as the temperature will vary as the fire is stoked, burns down, and is stoked again. But, generally speaking, the temperature in the chimney seems to be around 40-60°C - neither one thing nor the other, you would have thought. However, for mackerel, eels, and white fish such as cod and pollack it seems to work very well. I give them three to six hours, and just make sure they come out before they are too frazzled. My point is that smoking is by its nature an inexact craft, not a science, and therefore ripe for experimentation. A fish is 'properly' smoked if you like its finished taste and texture. If it is not smoky enough, smoke it some more. If it's too firm or raw, whack up the heat a bit. And if it's burned to a frazzle, better luck next time.
Choosing wood for smoking
Apart from temperature and length of smoking time, the other way to influence the results of your smoking is to vary the type of wood you use to produce the smoke. Almost all hard woods are suitable for smoking. Soft woods, on the other hand, especially pines and conifers, tend to produce a smoke that is not only unpleasantly acrid in taste but may also be carcinogenic. Stick to hard woods. Of these, oak has long been the favourite in the UK, and certainly has a distinctive and unmistakable flavour. But beach is also good, as are most fruit woods, especially apple and cherry. Some woods are especially aromatic, and if combined with other woods, even in small quantities, they will add their inimitable savour. Notable among such scented woods are bay, juniper and hickory - the latter is especially popular in America. You can also smoke very successfully over a peat fire.
The exact form in which your wood is burned depends on what kind of smoking you are doing. For hot smoking and rough smoking (as described above) over an open fire, large logs, or kindling, can be used as they come, but smaller wood chips or sawdust thrown on in addition will help increase the quantity of smoke, and therefore boost the final flavour of the food being smoked. But for more closely controlled cold smoking, fine wood shavings or sawdust are easier to work with. And if you are using the baffle-plate system described above, they are pretty much essential, as larger pieces will not smoulder without direct contact with flames. Hardwood sawdust mixes designed especially for smoking can be bought, but they are expensive, especially if you do a lot of smoking. Timber yards and joiners may let you pick up a few bags of sawdust from their floor for nothing - but be sure you know what kind of wood you are getting. (Once you have used it a few times, you should be able to recognise oak sawdust by the smell.)
The smoker in use
Maintaining your home-smoker while it smokes is largely a matter of trial and error, until you get the hang of the quirks of your own particular model. The objective, however, is straightforward: to generate a steady supply of smoke at a reasonably constant temperature. In the case of cold smoking, this is never likely to be much less than five or six hours (for mackerel, eels and kippers) and may be as much as a week (for a 10kg ham on the bone). Damp sawdust burns slower, smokier and at a lower temperature than dry sawdust, so always dampen your sawdust to maximise your 'smoulder time'.
Sometimes climatic conditions or too-damp sawdust can result in problems getting your sawdust going. In such circumstances an excellent trick to kick-start your smoker is to heat some sawdust in a heavy frying pan on the cooker until it starts to smoulder really well, then dash outside to the smoker and tip the smouldering stuff on top of the damp stuff. Once the sawdust is on the go, you should keep the fire under it low and the air fairly restricted: too much oxygen or too much heat and the sawdust will dry out, flare up, and be gone in a matter of minutes. If it's going too fast, add more damp sawdust and stir the pile a little. If the chamber is too hot, sprinkle a little water on the fire. For both these jobs, one of those gardening spray cans filled with water is a handy thing to have around a smoker.
Even the best-designed home smokers rarely burn for more than about three hours without needing topping up with sawdust or adjusting in some way, so you will have to check on it fairly regularly. On the other hand, the supply of smoke doesn't have to be constant. If you need to go out (or go to sleep!) while the smoker is on the go, don't worry about it. Just let it fizzle out, then re-light it when you come back. Beware, though, in the summer months: an extinguished smoker left outside and unattended for more than a few hours with food inside it may be found by flies, who will do their worst.