The Seedling Urban Evaporator is a Continuous-Flow Pan and thus More Efficient than a Lobster Pot
People responded so well to my last blog post that I decided to keep it technical this week. Let’s, as promised, talk about why a continuous-flow pan---like the Sapling Evaporator Pan, and the NEW Seedling Urban Evaporator---beat a flat pan for maple sugaring.
To address this question, I brought in Expert-of-Sorts, Andy Boutin, General Manager of Pellergy, and, conveniently, co-lessor of 157 Pioneer Center, Suite 1. As Andy was moving stuff around our shared warehouse, I shouted questions at him, and he shouted back, pausing every once in a while to draw me a diagram. Here’s how our high-volume conversation went:
Kate: People want to know why continuous-flow evaporators are more efficient than evaporating on a flat pan. I gather the answer lies in understanding a principle of physics called a “gradient.” I’m trying to figure out what a gradient is, what it has to do with sugaring, and how a continuous-flow evaporator exploits that principle to make more syrup in less time. Can you help?
Kate: Wait. What did you study again?
Andy: Marine Engineering and Naval Architecture.
Kate: Hmm. But that involved a lot of Physics classes, right?
Andy: Yes. There’s a lot of fluid dynamics in that education, with ships and man submersibles traveling through water at different densities. It’s relatable.
Kate: Sold! Why is a continuous-flow pan better for sugaring than a flat pan and what does it have to do with the “gradient.” According to Lord Google, gradient is defined as “an increase or decrease in the magnitude of a property (e.g., temperature, pressure, or concentration) observed in passing from one point or moment to another.” What does that have to do with the price of syrup?
Andy: Lord Google is correct, of course, but that's not how I would explain it. Let’s back up.
Gradient is “physics” for as you move through space or time, something that can be measured changes gradually over the course of that distance. So, on a hot summer day, in a house with no internal doors (or doors that are open), if you climb the stairs from the basement to the first floor, the first floor to the second floor, and the second floor to the attic, you travel through a temperature gradient. A gradient is a gentle slope, not a cliff, and is not the result of a physical barrier. So, when, on that same hot summer day, you cross the street and open a door to a nice, cool, air-conditioned house, you are not travelling through a temperature gradient – the change is not gradual and is the result of a physical barrier.
There are a number of gradients at play when sugaring, but probably the most important one for purposes of this discussion is the density gradient that results from changes in sugar concentration as water evaporates and sap turns to syrup.
Kate: OK, I’m with you. Are there density gradients no matter how you sugar?
Andy: Yes. But they don’t operate the same way in every pan. Envision a flat pan the same dimensions as the Sapling Evaporator Pan---20” x 30”---but with no baffles. Think about the pathway from sap to syrup in that pan. Put the sap in. Start the fire. Water boils off. You add more sap. Now you have a density gradient: the denser liquid is at the bottom of the pan and the less-dense liquid is at the top of the pan. Every time you add sap, that density gradient forms (and, by the way, you kill your boil). So you have to keep boiling and boiling until the entire pan is the same density, and then you draw it all off. That’s the batch process. The gradient works against you, not for you, when you batch.
The concentration gradient works FOR you in a continuous-flow pan, both in terms of efficiency and quality. Now take the actual Sapling Evaporator Pan---20” x 30” with two baffles---and what you have is a pan that operates as if it is a 10” x 60” pan, squashed over the firebox. Now: put the sap in, start the fire, water boils off, you add more sap to one end of the pan only, and you’ve rearranged the gradient into a flowing river, where the less dense liquid pushes the denser liquid toward the pour-off, instead of a stagnant pond with muck settling at the bottom.
Kate: That’s quite a visual. Thanks. And there are efficiency gains as well as quality gains, you say?
Andy: Yes. In the flat pan, the gradient is only as long as the pan is deep, with a baffled pan, the gradient is as long as the different channels all stretched out. The efficiency is in the continuous flow that the latter gradient arrangement allows for – there’s no time-killing start and stop to your boil. The quality gains are that when you do draw off, you are able to take off only one density of syrup, even while other densities exist in the pan simultaneously.
Kate: One last question. Is it just me, or when you Google “sugar gradient maple” does the internet try to sell you wigs and quilting fabric?
Andy: Um . . . It’s you.
That's all, folks!
The Sapling Maple Sap Evaporator is engineered for maximum backyard efficiency!
A few days ago, a prospective customer named Tom emailed me with the following question: “I love your maple syrup evaporators. But, without being a jerk, why should I spend $895 on a Sapling when some guy is selling a homemade barrel evaporator for $300 on Craig’s List? What’s the difference?”
I’ve now been corresponding with Tom for a few days. And I can assure you that he is most definitely not a jerk. Not only that, but his question is a very, very good one! So, without being a jerk, here’s what I told him:
First, the Sapling is engineered for maximum backyard efficiency. Although the Sapling is simply designed, it is engineered especially for sugaring, and has some of the advanced features of more expensive evaporators. Most importantly, the Sapling’s stainless pan is baffled, which allows it to operate as a continuous-flow evaporator. Continuous-flow evaporation merits a blogpost in itself, but suffice it to say that this configuration allows syrup to be drawn off and sap to be added without emptying the pan. The continuous flow is more efficient than boiling off sap in batches, or pouring the boil from pan-to-pan.
I've talked to a LOT of people who have used the kids of homemade barrel evaporators Tom is talking about. Typically, those evaporators use a cast-iron, barrel-stove kit and hotel pans, both widely available items, to convert the barrel to an evaporator. The barrel-stove door does not have as much space for air intake as the Sapling’s specially engineered door does (making it harder to keep temperatures optimal for sugaring), the legs are shorter (requiring more bending on your part), the exit pipe comes out of the top of the unit rather than the back of the unit (leaving less surface area for boiling, which means slower evaporation) and, MOST importantly, the pan(s) are not baffled, meaning that you have to batch your boil, or pour from pan-to-pan, instead of doing a continuous-flow boil. From the (literally hundreds of) conversations I've had, I'd say that the Sapling, which boils at anywhere from 4 to 8 gallons of sap off per hour, depending on conditions, is easily twice as efficient as a comparably-sized batch operation.
Second, we stand by our Saplings, which are built to last. Our Saplings are coated with a high-temperature powder coating that is both durable and clean for the environment. And, all fasteners and hardware on the exterior of the Sapling are either powder coated or made of stainless steel. Homemade barrel evaporators probably don't have stainless fasteners, typically have cast iron pieces that rust, and are not at all likely to be powder coated.
We are a going concern, and are in this business for the long haul. Our reputation is important to us, and we support our customers whether they are happy with our products or not. (So far, so good!) That homemade barrel evaporator guy may not be as responsive to your requests for customer service as we will be. Take Tom, for example. He asked a question, and got an essay!
Third, the Sapling is multifunctional and can be accessorized. The Sapling is not just an evaporator! Each unit comes standard with grates that convert the Sapling into a wood-fired grill. And now, with the purchase of the Sapling Smoking Package, the Sapling can be a smoker too! Soon, a Sapling-shaped heavy-duty cloth cover (like a grill cover) will be available for purchase, and we hope to launch a warming pan that will fit neatly on the back of the Sapling in time for next sugaring season. The Sapling is unique among all evaporators for its multifunctionality; the current and future availability of Sapling accessories sets it apart from homemade units of all kinds.
Fourth, the Sapling was built with safety and the environment in mind. This is my last-but-not-least point. Saplings start as new, unlined, unpainted steel. They are assembled, media-blasted, powder-coated and outfitted with a stainless evaporation pan bearing lead-free welds and a lead-free pour-off valve. Our operations are so environmentally responsible they require no permitting.
As far as we are aware, homemade barrel evaporators are made with barrels that have been used, lined, and/or painted. Such barrels are widely available at little or no cost. When we were in our R&D phase, we started with used, painted barrels too. We learned quickly that this would be a mistake in production.
To start, in order to put high-quality, high-temperature paint on used barrels, you have to clean off the old paint, which is not suitable for high-temperatures. Otherwise, the old paint will peel off right under the new paint on the first burn. This is extremely difficult, dirty, and time-intensive work that we suspect lower-cost barrel evaporator makers do not engage in. Unfortunately, many people who have made their own evaporators have reported to us that they burned the old paint off before applying the new paint. We do not know whether homemade barrel makers engage in this environmentally suspect practice, but we most-certainly do not.
Even as we were bemoaning the work involved in rehabbing an old barrel, someone was mistaken (or less than honest) about what had been in one of the used barrels we purchased and we had a health and environmental issue on our hands the moment we opened it up. We handled it responsibly, and everything turned out fine, but it put us off used barrels for good. Now, we doubt whether anyone would work on and sell to you a barrel that smelled as bad as this one did, but nevertheless, we feel REALLY good about being able to tell people that we use new, unused, unlined, unpainted barrels to make our Saplings. You do not know where that used barrel has been! And we are not messing around with safety!
Tom is still thinking about whether to become a customer, but I appreciated his inspirational question so much that I offered him a free Sapling cover if he came our way. So take this as a not-so-subtle hint, readers. Send me your thoughts!
And thanks, Tom!
On Teaspoon of Sugar, we write about maple sugaring, maple syrup, starting and running a small business, and living the sweet life here in beautiful, downtown Montpelier, Vermont.