Maple Sap Evaporator for Under $100 and Finished in Under Three Hours

My family loves maple syrup. Oatmeal, pancakes, waffles, fancy coffee drinks, home brewed maple stout, maple oat bread... the list goes on. My wife uses a fair amount of maple syrup in her bakery and typically will purchase three gallons at a time when she puts in orders. So, it goes without saying that we use a lot of the golden elixir. Growing up in upstate NY my family tapped the trees on our 11 acres of land. This was no sugar bush, more like a "somewhat sweet expanse" because the trees were so far apart from each other. We used spiles with five gallon buckets hanging from them and then trucked them back to the house using either a sled or an ancient twinkie-shaped snowmobile that had a tendency to flip over. Once the sap got back to the house (assuming it wasn't lost from the rouge snowmobile roll overs) we set about boiling it over a fire, on the grill, or in a makeshift fire pit, typically in a pot that was just as tall as it was wide (not a good ratio). We did end up getting some sweet syrupy goodness from our efforts, but at a 40 to 1 ratio, we typically made no more than 1/2 to 1 gallon. It's a lot of work, requires a lot of energy (both from the humans and the firewood end), and takes a heck of a lot of time. The end of the boil was typically brought indoors with a candy thermometer in hand and high hopes. If all went as planned we ended up with a beautiful amber tree-juice that would decorate our pancake dinner that night... if all went to heck, well then you ended up with a burnt pot of burnt sugar, and, if it's possible, burnt feelings.

Fast forward 25 years and for some reason that nostalgia (at least when we were successful) still sticks in my head today. Now, with my own two kids, a few acres of land, and about 40 red maple trees I want to relive a bit of my past and give my kids a chance to enjoy the splendors of making maple syrup, or at least get the experience. Yes, I know, sugar maples are much better suited to making maple syrup, but I am not a tree magician and the sugar maples I have on my property are pretty scrawny at the moment. Most of my trees are concentrated in a relatively close knit area so the lugging of somewhat sugary water will be a bit less daunting. I might even put together a sap collection system, but will have to either overcome gravity and pump the stuff up to my house or just reposition the boiler at the lower corner of my property. Whatever the case the biggest obstacle was finding a way to boil it all down as efficiently (and cheaply) as possible. I checked out a number of plans and videos online and ended up settling on a 55 gallon barrel evaporator using an old drum, a wood stove kit, some piping, and a couple of steamer trays. I was able to get the barrel free from a friend, the wood stove kit was $45, and the two used stainless steel evaporator trays were $15 each at the local restaurant supply store. With all said and done, I was able to build a maple sap evaporator for under $100 and it works fantastic so far... even if it's only been tested with snow and water :)

I am going to give you some details on how I went about building this maple sap evaporator to help you build a similar one. There are, of course, heaps of ways to modify and improve the evaporator but with a price tag under $100 and a total build time under three hours it's perfect for the initial experiment. As an added bonus, you can use the stove as a source of warmth during those winter sledding parties before the sapping season has officially started. Just take the steamer trays off and you have a perfect wintertime fire or maybe find a way to make some amazing chocolate milk in the steamer trays...

Materials:

(1) 55 Gallon Drum / Barrel with both ends still intact

(1) Barrel Stove Kit

(2) Stainless Steel Steamer Trays

Tools:

Grinder and cut off wheels

Jigsaw and metal cutting blades

Drill and drill bits

Wrenches to fit bolts / nuts

Tape measure

Sharpie

I am proud to say that I didn't have to do this last minute! The sap doesn't run for another couple of months here in MA and I made sure to secure both the barrel and the stove kit way in advance. A friend of mine had a couple of extra barrels kicking around and offered up the once shiny blue one that I used for my evaporator. This barrel had one solid end and one end with a cap and band clamp. It wasn't exactly what I was looking for but I decided that the band clamped end might actually be beneficial to clean out ash even easier. I might need to use some fiberglass gasket rope to seal up the clamp-end of the barrel but at the moment it is working great without it. I ordered up my barrel stove kit and had that well in advance so that when a warmish day occurred I could get out there and put the whole thing together.

I would check out Craigslist or another used goods place for the barrel. You should be able to get one for between 10 and $25. The stove kit was another $45 when I bought it and there seems to be a number of sources you can get it from. Make sure to open up the stove kit well in advance of the day you plan on building to make sure you have all of the parts needed to complete your build... there might be some nuts and bolts that are missing or a broken part since it is cast iron.

The first step in building the stove is to cut your initial opening in one end of the barrel. The instructions suggest using the end with the plugs and using one of the additional plugs as an additional air intake to help keep the fire raging. The barrel I used did not have plugs but had an end with a clamp. I decided to use the non-clamp-end side of the barrel to make the opening for the door. After centering the door directly on the barrel we opened up the doorway and marked out exactly where we needed to cut the opening using a sharpie. You will need to add some additional space below the door for the flue slide or you can leave that until the end and just drill holes into the barrel for the flue (this is what we ended up doing). We used a grinder with a cut off wheel to make the straight line cuts on the barrel and then finished up the cuts with a jigsaw with a metal cutting blade installed in it.

The next step is to add the legs to the barrel. After removing the band clamp and the end of the barrel we used a couple of pieces of firewood to stabilize the barrel so it wouldn't roll and we centered the door so that it was parallel to the ground. We marked where we wanted to put the legs with a sharpie and then drilled the holes for the bolts to pass through. We kept the screw heads in the barrel and the nuts and excess screw thread on the outside so that they wouldn't interfere with putting firewood into the barrel. Attach the legs, tighten down the screws and nuts and move on to the next step.

Now that you have your opening cut, the legs attached, and your barrel able to stand on its own you can attach the cast iron door to your opening. Put the door on and mark where the bolt holes go and then go ahead and pre-drill for the bolts. Bolt the door on and you are ready to move on to the next step.

The final step is to attach the cast iron collar to the top of the barrel so that you can later attach a stove pipe. The collar has a damper built into it so that you can adjust the burn of your wood in your firebox. Pretty simple again, just put the collar on top of the stove near the top back opposite of your door and trace the interior circumference of the collar and mark out the bolt hole locations while you are at it. We cut out the collar's circle with the jigsaw and then drilled out the holes. Attach the collar as far back on the barrel as you can so that you can ensure that you have plenty of room for the evaporator trays, which, by the way, is our next step!

One of the best ways to evaporate sap is with a large shallow tray over a flame. Boiling the sap in a large soup pot or kettle works, but takes a long time since there is so much less surface area. Since I only had so much room on the surface of the barrel I planned on using a couple of stainless steel steamer trays as my evaporators. Although, they are not super shallow, they definitely are not soup pots and a lot of other folks are doing a similar thing to build their sap evaporators.

The first step was seeing exactly where we needed to cut the barrel so that the trays would sit neatly over the flame. We centered the trays and then used a ruler to make a straight line from the side of the evaporator tray down to the barrel. We marked this with a sharpie and then made a level line across the entire barrel from there. This line would represent the maximum depth of cut down the side of the barrel we could make, but would ultimately leave the evaporator tray sitting right "in" the fire. What we wanted was a lip where the trays could comfortably sit (if having a raging fire under you is ever comfortable that is). So, from the level line we measured up another three inches parallel to the length of the barrel. This is where we would cut the rectangular hole out of. Using the grinder we cut a line down the middle, then cut the lines perpendicular to the middle line. We cut all the way down to the original level line because we are going to use that are as a flap to fold down to hold up the trays. We then cut the line that was 3" above the level line and removed the cut panels.

Now that you have the rough opening cut out for the evaporator trays you will need to make a little lip for the trays to rest on. Using the grinder we cut small little cuts near the folds of the barrel so that we could easily fold down the lips we created along the level lines. My brother had a good idea to use a scrap piece of the barrel to put down the middle to help seal in a bit more of the heat and prevent the flame from really flying through the gap between the two evaporator trays. Nothing fancy, just a strap of steel with a couple of rivets used on either side to hold it in place. We then put the trays in and began the process of fitting them more snugly. We used the angle grinder with a grinding wheel to grind any high spots keeping the trays from sitting flush.

The final step after you have fitted your trays is to fit a stovepipe in the collar you attached a few steps ago. This stove will only be fired outside and I happened to have some extra 6" steel piping leftover from making my dust collection system in my shop. Not the best pipe for a stove, but being outdoors it will work just fine.

We started off with a small fire using some pine kindling just to make sure that everything worked fine and dandy. We put some snow in the evaporator pans so they wouldn't overheat and we could melt snow... feels like we are doing something then while burning wood. We ended up adding more firewood to the barrel to start the process of burning off the paint on the barrel. Overall the stove drafted perfectly (after we remembered to drill the holes for the air intake on the front door). We were able to put some massive logs in there and really get them burning with no problem. I guess we just need to wait for those buds to form on the maples and the first signs of spring coming around the bend... sadly that feels a long ways off for now. As a bonus, we can use the evaporator as a nice outdoor oven to warm our hands when we are playing on our backyard sledding luge (that's the big snow pile behind the stove in the pictures). Happy tapping and boiling everyone!