[Part 3 of a series about designing and building my own cold smoker. Part 1 is here, part 2 is here.]
Fire needs air to burn; and the smoke needs to escape so it doesn’t choke the fire. So you need a hole to let air in, near the burner, and a hole to let smoke out, near the top of the chamber. In my case I just drilled a bunch of small holes. At first I found I hadn’t drilled enough, as the sawdust kept going out. In the end I drilled about 90 5mm holes (no special reason for the size – that’s just the biggest suitable drill bit I have) for each. I based the number on another smoker design I found on the web – which had much larger holes but fewer of them. If you’re going to do it, and you happen to be using a different sized drill bit, or perhaps cutting a single hole, then I’d advise using a little maths to make sure you’re getting a similar overall amount of ventilation, as there’s nothing more frustrating than trying to light your smoker only to find it keeps going out.
When I tried my first smoking run there were about a fifth of the holes there are now. Fire needs air!
It’s nice to be able to control the exact level of ventilation, as this enables you to control temperature and burn speed. I fitted a couple of pieces of spare hardboard which I could use to cover some or all of the holes.
5. Where to store the food
You have a number of options for how to store the food in the smoker. Traditionally you’d hang meat or fish from hooks. I did consider fitting a couple of bars, like you’d get in a wardrobe, and hanging the meat off those with butcher’s string. But in the end that seemed like a comparatively labour-intense option (and not suitable for cheese and other non-meat products) compared to a shelf.
You don’t want one side of your food up against a solid surface, because the smoke won’t reach the food on that side. That’s easily solvable by using a rack. You can either make your shelf out of, say, an old oven shelf (if that happens to fit nicely in your smoker) or you can do what I did and put in a solid shelf and sit the rack on top of that. We had a bunch of roasting and grilling racks lying around, so I just used those.
The shelves in the original unit were a bit too small, and the ridges at the back would have got in the way.
I was intending to sit the units upright, and use the shelves originally intended for baked beans and whatnot to sit the food on while it smoked. But (a) the shelves were a bit narrow and the gaps between rather small, and (b) at each level the cupboard had vertical dividers designed to stop things slipping down the back of the cabinet, and to run screws through to fix the unit to the wall, but which in our smoker would just get in the way and prevent larger items from straddling the two wall units. So at Becky’s suggestion, I turned the unit so that one of the doors was facing upward (the other door facing down of course, as the original kitchen units were now back-to-back), and cut some hardboard shelves, which sit on top of the ridge between the two units. I added a couple of stronger bits of wood to act as beams providing extra support to the shelves.
This is a top-down view of the smoking chamber. I used a couple of spare bits of wood as beams to support the hardboard shelf (which is not shown in this picture)
6. Spreading the smoke
To judge by smoker designs I’ve seen in books and online, this is an optional extra. But it seems important enough to mention. Simply put, if you just have your smoking fuel sat under some meat, at any given moment the smoke will be arising from a fairly small area of the burner. It will waft upwards and, most likely, strike a fairly small area of the smoking chamber. You’ll end up with some of your food getting the full force of the smoke, while the rest maybe doesn’t get any smoke at all.
The solution is pretty simple: you put a barrier between the fuel and the smoking chamber, with lots of holes in it through which the smoke can seep. Rather like the way a shower head spreads water which would otherwise come out in a single jet, this spreads out the smoke.
The shelves have dozens of holes drilled so the smoke spreads out.
For our smoker, I simply drilled a bunch of holes in the shelves. Since the shelves more or less completely covered the gap between the burning chamber and the smoking chamber, this prevented the smoke from just going straight up, and instead spread it around nicely.
Getting a thermometer for a smoker is surprisingly difficult. Well, to be fair – not difficult at all, if you know where to look. I’m going to shortcut that process for you.
You can get lots of different kinds of thermometers. Meat thermometers, medical thermometers, oven thermometers, fridge thermometers. All of these have problems with them of one kind or another. Wrong temperature range (cold smoking is about 10 C to 32 C, with the ideal temperature in the mid-20s); not for measuring air temperature; can’t be read without opening the smoker and dispersing the smoke. But as it turns out, there is a thermometer that works perfectly, and is quite cheap.
Surprisingly, the one I ended up getting is a terrarium thermometer, for reptile houses. It has a probe with a longish cable so you can measure the inside of the smoker without opening it up, a digital readout that will do Fahrenheit or Centigrade, and measures a range of temperatures from -20C to 110C. Best of all, it cost less than £10. Here’s a link to the one I bought.
Best. Thermometer. Evar.
8. Other stuff
If you’ve done the above, you’ve got a working smoker. But there’s a few little nice-to-have things that you might want to consider.
First, where to put your smoker. It’s going to leak smoke over the course of many hours, so you probably don’t want it in the house. It has holes in the top, so you don’t want anywhere it’ll be exposed to rain. But you want at least a little ventilation so there’s fresh air to keep it burning. I’d also suggest somewhere with a bit of spare room for when you’re juggling trays of meat, gas rings, matches and so forth; and somewhere with a light so you don’t have to add a torch to that list, as you may find yourself refuelling after dark.
Second, consider adding a viewing port, or better yet a door big enough to slide the burning tray in and out. In the early days you’ll find yourself frequently wanting to check if the fuel has gone out, and you don’t want this to be difficult or to lose you a load of smoke. To access ours you have to open the lid, remove one of the two shelves, push aside two beams and then reach right to the bottom of the smoker. The only way to view the burning tray without following a similar process is to attempt to shine a torchlight through the ventilation holes while simultaneously looking through the self-same holes. Needless to say I’m already thinking about how to fit a viewing port to save me all this hassle.