Monday, April 18, 2016

Turning Alaskan Birch Sap into Syrup, Part 2

(This is Part 2, focusing on cooking the sap down to syrup.  To read about collecting the sap, please enjoy the prior article).

In our neck of the woods, the sap started running on April 2, 2016, more than 2 weeks earlier than in recent years and 6 weeks earlier than a particularly late spring several years ago.  Whenever Nature decides, we have to be ready.

Assembling the evaporator
Fortunately, we had strung the collection lines among two dozen trees in February and early March.  After that, Bryan started to assemble the "woodstove" he bought from Leader Evaporator (in Vermont), which consisted of a sheet metal exterior, about 600 pounds of heat resistant bricks (some of which he had to cut to fit), and a short, metal chimney.

Unfortunately, the masonry cannot be cemented together until the temperature rises above the mid-40s, which did not occur regularly until late March, and once that occurred, it started to rain!  Every day for a week!  So that set us back a bit.

The evaporator was finally finished and the first test fire ignited on April 1.
The very next day, we discerned drops of sap flowing down the plastic lines to the collection tank next to the wood  stove. Phew!  Perfect timing.

2.5 quarts syrup/40 gallons of sap,
served with goat cheese
and condiments. Yum!
After that, I became a “syrup widow” for the next 12 days.   About every other day, Bryan headed out to what other people might call a “Sugar Shack”but in our case was just an open deck on the far side of the shower house, at the low point of the row of trees we had tapped and strung together with food grade tubing.  There, next to the evaporator and the 55 gallon collection tank, he set up an outdoor office on a canvas camp table, plopping down his computer, phone, paper and pens, a bag of snacks, and a walkie talkie to reach me when he got bored or needed something.  (Our power for communications is supplied by a 120 foot power tower for solar and wind power he built in 2007).  For 8 or 9 hours, in between calls with finance and consulting clients in time zones far, far away, he hauled sled loads of birch logs from the wood corral, stoked the fire, and poured gallons and gallons of sap into the cook pan.  In the mornings, the temperatures were in the low 30s, but by early afternoon, he could peel off his parka and hat and enjoy the temperature for a mostly sedentary day. When he was ready to wrap things up for the day, I would deliver cups of our homemade wine (for me) and beer (for him) and some goat cheese and crostinis, drizzled with some of the prior day's syrup, for a celebratory cocktail hour in the pretty lake-side, wooded setting.

This is a great time of year for such a time consuming but lazy outdoor endeavor.  The snow is so soft and slushy that we can't walk around without cumbersome snowshoes.  Not enough ground is exposed to do any yard work.  And yet, for us, the sap run is the first sign of spring and we WANT to be outside, doing something.  It is fun to watch our domestic ducks plunge their beaks into the muddy margins of retreating snow and thoroughly aerate the yard, foot by foot. We see pairs of honking swans and silent eagles circling overhead, seeking prime nesting spots, hear howling coyotes, and see the first squirrels emerge from hibernation. This year, we have not yet heard the distinctive clacking of Sandhill cranes.  Where are they?

Note sap reservoir, top, with faucet
to 3 channel cook pan, below
To picture the process of turning sap into syrup, let me describe the evaporator, which is not a generic style but purpose-built.  The stove top is actually a removable cooking pan nearly 3 x 4 feet, cunningly designed for reducing hundreds of gallons of sap to syrup (100:1) without burning the increasingly sugary liquid.  The trick is a maze-like interior of three channels. Above, straddles a removable rectangular reservoir, about 3 feet by 8 inches by 8 inches.  Into it, Bryan pours gallon after gallon of sap that has accumulated in the adjacent collection tank. The reservoir has a faucet on the corner to drizzle sap into the cook pan below at whatever rate maintains a pan depth between 1- 2 inches.  As incoming sap pushes the liquid through the maze, one can see that the first channel is clear and each of the subsequent channels is increasingly filled with a darker color, because the interim evaporation has concentrated the sap into a thin syrup.  The “end” corner of the cook pan contains another faucet from which the cook can drain hot syrup into a smaller pot. Great idea!  This is much safer than lifting and pouring the whole boiling, bulky pan!   From my cabin window, I can see that Bryan is surrounded by smoke from the chimney and steam from the syrup.  The vicinity smells great, like smoky caramel.
Collection tank in front with blue
drip tube, evaporator behind

From the 30 taps we inserted in 2 dozen birches, the tank filled slowly, drop by drop.  About every other day we accumulated 40-45 gallons.   The outdoor evaporator reduced about 40 gallons of sap to 2 gallons of “near-syrup” (95%) over 8 or 9 hours, consuming 2-3 loads of wood (about 30 logs).  As many cooks know, reducing liquid in a stock or sauce is always faster at the beginning than at the end.  So, too, syrup.  On the second day, Bryan poured two gallons into a spaghetti pot inside on the propane stove, where it took another 8 or so hours to reduce from 2 gallons to about 2 quarts! (I will be interested to learn how much faster the propane tank empties than in prior years).  

During the last hour or so, when the syrup turned thick and dark and started “smelling right,” Bryan pulled out his hydrometer to test density (Baume scale) and percentage of sugar (Brix scale).  The syrup tastes delicious even when thin but without such a measurement, the syrup is not shelf stable - excess water percentage degrades the product over time.  The kitchen smelled so good on these days that I stole a cup or two of the evaporating syrup to flavor oatmeal cookies, BBQ sauce and anything else I was cooking at the time.  Tonight, I used it to flavor a vinegar/peanut butter/srirachi/soy sauce topping for smoked chicken and rice.  Birch sap is full of nutrients and the syrup concentrates them, so I feel virtuous using it!

When we see that the birch trees are just starting to bud, it is time to wrap up the sap/syrup collection process.  For us, that was  April 14.  Bryan gently removed each tap and assessed the condition of the hole and the clear, plastic taps.  Four taps were filled with a milky white substance, which indicates that bacteria entered the hole and were proliferating.  Had these colonies grown enough to enter the drip tube and flow to the collection tank, they would have adulterated 40 gallons!  The next several days, we revisited the trees to see which ones were still dripping and which holes healed up fastest, and made notes for next year.  All looked good.  Our first syrup season ended with about 1.2 gallons of a tasty product, gathered during lovely weather when there was not much else that we could do.   

Conclusion:  Collecting sap in small volumes is cheap and easy for an individual or small family and I encourage it (see prior article).  Turning that sap into syrup requires a heck of a lot of work, time, and money.  We spent about $2,000 for the equipment to make our first gallon of syrup.  As Bryan said, we have never drunk a wine so expensive!  On the other hand, every husband I know has some expensive enthusiasm, such as a media room or a whole garage full of equipment for sports, hunting, fishing etc. 

If my husband's expensive hobby involves traipsing through a pretty birch forest to tap trees and then sit by a fire for several days to boil the resulting sap, so be it.  It is a harmless and possibly useful enthusiasm.   However, I totally understand anyone who finds this endeavor ridiculous and would rather just buy a bottle.  Do so!  Birch syrup is a rather rare, boreal forest novelty I encourage travelers to try. (In fact, I never even heard of birch syrup until I moved to Alaska and visited the Kahiltna Birch Works, near Talkeetna,and bought several of their tasty products, not just syrup but also syrup flavored mustards, jams, and sauces, which have inspired me. 

For us, we now have a rather heady “sunk cost” to amortize over the next dozen winters so you know we will be making more syrup.  As any gardener knows, each season is different, so I anticipate that our syrup will vary, too.  Since it should last many years, I look forward to comparing batches from one year to the next.  I would describe this year's output as having a “grown up flavor” – it tastes darker than maple syrup but lighter than molasses.  It is not a simple sweet, but nuanced.  Since my husband is a home brewer, his analogy is that maple syrup is like an amber ale, while birch syrup is more like a porter or stout. 

Bon appetit!


  1. you are such a great writer Laura. Loved reading this! now bring on the pancakes!

  2. I totally have enjoyed all your writings. I can always read through and feel that sense of well being you have from your life of learning, hard work and accomplishment. So I know you are having fun too. Your sharing transfers a bit of all that me.

  3. I recall a blog about the huge size of fish in rivers and lakes around your place "Up at Latitude 61"..
    I am nor only a fan of you guys .-in my school classroom I bragged to my kids about you when strengthening up courage, perseverance, loyalty and determination values and ....they went.- ...........................keep going .. Sr. Garcia........... tell us more !!!!.
    .. you guys are fantastic !!!