The Boiling

[unicornduke]

Here's the thing about maple sap: it is much much sweeter than all other tree saps (I think), but it is still 1-2% sugar. There's some information out there that maple trees in the middle of fields without any competition can get up to 4% sugar.

Maple syrup is 66% sugar minimum.

So typically, the ratio is around 50 gallons of sap to make 1 gallon of syrup. Depending on the sugar content, this may be higher or lower. On a small scale, someone sets up a pan of sap over a fire, sits around and drinks alcohol while adding sap every so often and at the end, you might get a gallon or so of syrup. As soon as you move up in scale, then you move to continuous flow syrup production, where the sap is flowing in all the time and syrup is drawn off every so often.

We have the syrup production set up in the milkhouse of our barn. I found out recently that not everyone know what a milkhouse is, my experiences are not universal! This farm used to be a dairy, so the barn was set up for milking cows and the milkhouse is an attached room or building with cinderblock/stone whitewashed walls, concrete floor and a drain. In the milking days, this is where the milk would be stored in tanks for easy chilling until the milk truck comes to pick it up. It is easy to clean, away from the bacteria of the cows and easy to keep birds and other pests out of. (sidenote: do not ever drink raw milk unless you are the farmer or really really really trust the sanitation practices of the farmer (don't do this, raw milk farmers are fucking wackos) because cows have so much bacteria and poop pretty much on their udders. Pasteurization is a miraculous process to prevent illnesses)

To start, we have the sap run into 250 gallon food safe, cleaned totes with a filter. Once they are full, they get brought from the mountain and placed for gravity feeding into the milkhouse. The setup is beautiful, professional and normal. haha

It works quite well actually. In the photo, it is a little hard to see, but we've got 1.5inch tubing lines with quick disconnects that lead from the totes to the line and into the window of the milkhouse. It is wrapped in black foam insulation and there is heat tape in there because the line can freeze if we boil when the weather is below freezing. We only run one tote at a time and then switch the line over as one runs out.

My parents bought the biggest evaporator they could fit in the space, which is a 100 year old thing from Vermont. The pans are newer. The closer silver chimney is actually a steam vent for evaporating water and the fire chimney is the black thing behind it, so the fire is built underneath and the hot air flows from the front to the back and out the chimney, heating under all the pans on the way out.



Once in the milkhouse, the sap runs into the tank, following the path of the red/orange line into the sap tank via tubing and a float valve. The float valve is in the little rectangle box where the orange line ends. This controls the height of the sap in the tank because the sap boils in that tank and it will scorch if the level gets too low. The height indicator is circled in orange and you can see the level of the sap. It should be around the level of the line on the tank and the float valve can be adjusted up or down. Sometimes it just has a mind of its own and decides not to work properly. The sap feeds from the tank into the boil pan following the blue line where there is another float valve. This adjusts the height in the boil pan, which we manually check with a metal ruler.



The boil pan is the real place where sap becomes syrup. The temperature of the syrup has to be at least 212F to maintain boiling and it sits and boils for quite a while. Because this is continuous flow, the sap is always coming into this pan, flowing through the sections and condensing on one side until it gets so dense that it starts to boil hotter and hotter until it is at the correct* temperature and then flows out into the filter pan.



*Correct temperature is measured by the temperature that the syrup is at murphy reading + 1 to 2 Brix. I did not get a photo of this, but basically, we have a tube with a temperature probe on it that tells us what the Brix should be at based on the temperature that the syrup currently is aka the murphy reading (not sure this is the official term but that's what we call it). We pop a brix hydrometer in there and it floats to tell us the current brix level. If it is too low, we adjust the temperature draw level up and if it's too high, we panic and toss sap in to cool the pans down. The correct temperature for draw off depends highly on barometetric pressure because that determines the ability of the bubbles to escape into the air or something like that. Before the latest storm, the correct temperature was 220.4. After, it was 217.5. Hugely important to check a lot because it can change over the course of a day. Once we have that temperature set, the valve will open automatically once the temperature is reached. In the above photo, the temperature probe is circled in red. In a system without an autodraw off, you have to manually open the valve.

Once in the filter pan, it filters. The sap contains nitrate, it is black and gooey and no one wants to eat it. Once the syrup gets through four to five filters, it is clearish and delicious and extremely hot. We drain it out of the filter pan into pots with lids and then they sit to be bottled.



The thing about boiling syrup in this kind of system is that it has two modes: the doldrums and the draw off.

The doldrums are when we get started and after a draw off of syrup where the boil pan temperature is 213-215F and it just sits and boils. Things to do during the doldrums:

• Feed the fire every 8 minutes - fire must be roaring hot, long sleeves and welding gloves required, loud timer running
• Check the sap level - make sure it is near the line on the outside of the pan, check that the float valve isn't stuck
• Check the syrup level of the boil pan - make sure it is around 1.25 -2 inches depending on comfort level/weather and adjust float valve as needed - this can change depending on the day!
• Empty the condensation bucket - this is the runoff of the hood over the sap pan
• Check that sap pan and boil pan aren't foaming over - both pans will foam up and overflow, adding a de-foamer 1-2 drops fixes this
• Check the level of sap in the totes
• Make sure any syrup in the filters is filtering and remove top filter if too much niter has built up and is clogging it
• Fetch wood as needed

Most of the doldrums checks takes no more than a minute and I don't do the full checks every time, usually a bunch of it will be every other fire feeding or so. It leaves around 6 minutes of sitting there. I read on my phone, knit or split wood. Turns out, you can split a lot of wood in less than five minutes at a time. I also have an excellent sense of when five minutes has passed.

Once the doldrums are over, the boil pan temperature will generally steadily rise. It can spike, so once the temps start getting above 216, I stop splitting wood as much because everything requires a closer eye. The pans will foam more and that can happen quickly.

The draw off phase tends to start around 217F, where then I fully stop leaving the milkhouse (except for grabbing wood, I'm always doing that) unless I need to switch a tote or something urgent like that. Draw off phase includes the following:

• at 217 - start testing Brix every .5 or 1 degree
• Defoam pans as needed
• Have the Oh Shit sap mug and bucket full and on hand
• Once correct temperature has been decided, make sure lid is off filter pan so syrup can run
• When syrup hits draw off temperature, make sure valve actually opens - the syrup can crystallize in the inside of the valve and stick it shut - big Oh Shit moment because if the syrup can't draw off, the temperature will keep rising and the syrup will scorch because it can't leave the pan. This is when you dump so many mugs of sap directly into the pan until that buys you enough temperature to unhook the valve and clean it out
• keep testing Brix as it draws off into filter pan to confirm good temperature
• monitor the temperature very closely, if the pan temperature gets above 1 degree above draw off temperature, dump one mug of sap into the pan to drop temperature because it will continue to increase for 5-10 seconds before sap drops temperature into the safe zone
• stand by the pan and watch everything like a hawk

The draw off is extremely stressful because it is really easy to scorch the syrup and pan if everything doesn't go exactly correctly. The syrup will draw off a bunch, the float valve will let more sap into the boil pan and after a bit, the temperature will drop back down to the doldrums. This cycle repeats every hour or so.

With good dry wood and good syrup, we will boil 60-80 gallons an hour and get up to ten gallons of syrup a day. This would be an all day boil, where we get the setup done and fire started by 8am or so and boil three totes of sap. This is exhausting and we try to trade off boiling and other tasks like fetching more totes from down the road, cleaning out empty totes and getting them set up to collect and some other misc things. Wet wood slows us down to 30 gallons of sap boiled an hour. The sap runs off the mountain generally 30-40 gallons an hour when it is warm.

Tons of things can go wrong. Monday night during crafting, my dad sent an SOS text and I literally ran to help him, he went to change the totes over and the new tote was missing the correct quick disconnect valve, so I monitored in the sap house, while he found another one. If it had taken longer, I would have dumped the sap bucket in the sap pan or started dumping straight water in. Scorching the pans means stopping the whole system, taking everything apart and cleaning the scorch off. Then the draw off started and the valve was stuck, so I kept dumping sap into the pan while he got the valve off and cleaned and then the draw off went smoothly after that.

We get sap run until the trees start to bud and the syrup will taste leafy. Anytime we get 2 totes full and the sap will run that day, we start boiling. The startup procedure from go time to first draw off of syrup is around 3 hours, so we try and do long days. We can't really store sap very long due to the bacteria in it, which will start to ferment the sap if the temperatures are too warm. With temps freezing overnight like right now, we can have the sap sit for 2-3 days.

After this, we take the pots to the church and bottle it, which is much less stressful.

Comments

[which_chick]

That's a really informative write-up! I only have a couple of questions.

First, you have the sap run into the big white liquid boxes. I take it that these liquid totes are deployed out on the mountainside at the end of the sap pipe runs?

If they hold 250 gallons when full-ish and they're deployed out there in the wilds, how do you get them to the gravity-fed milkhouse-adjacent staging location in picture 1? They're gonna be way too heavy for a person to move without equipment. Bobcat? Forklift? Tractor with fork attachment?

What do you use for filters? You mention filters at several points in the process. Are there purpose-made filters for this?

What size containers do you bottle? I'm assuming something like pint, quart, style of a thing? What size do people most to buy? Are you selling mostly direct to consumers, or do you do wholesale as well?

(It's ok to tell me to go pound sand for anything you don't feel like disclosing, I'm just curious about maple syruping works as a farm business. I don't know anybody who does it and it's very interesting as a process. I also ask beekeepers a lot of annoying questions.)