This picture guide walks step-by-step through the process of performing the finishing boil for maple syrup.

After harvesting your maple sap and doing the initial boiling, it is important to pay close attention as you near the end of your boiling. You will need to make sure that the syrup hits just the right temperature without boiling over!

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Finishing Boil for Maple Syrup

The final stage of boiling down sap, often called the ‘finishing boil,’ is best done in a controlled way (i.e., on a stove) so that you can maximize the likelihood of producing perfect maple syrup that hasn’t been overdone (creating crystals or ‘rock-candy’) or underdone (watery syrup).

It can also be more conducive to bottling the syrup in a food-safe way.

What You’ll Need:

Summary of the Steps

We will follow these steps to perform the finishing boil on maple syrup:

  1. Tap your Maple trees and collect the sap.
  2. Boil the majority of the water off on an outdoor boiling setup.
  3. Pre-filter the sap to remove larger debris.
  4. Boil the Sap until it reaches a temperature of 215°F on a candy thermometer.
  5. Filter the syrup with a mesh syrup filter.
  6. Continue boiling the sap to a temperature of 219°F.
  7. Drip a few drops of syrup onto the viewing slide of a refractometer and read off the sugar content.
  8. When the syrup reaches a sugar content (brix) of 66%, stop boiling.
  9. Allow the syrup to cool to 190°F, then pour it through both a mesh filter and a damp synthetic filter.
  10. After filtering, and while still hot, pour the syrup into sterilized jars or bottles for long-term storage, or put it into the refrigerator to enjoy immediately!

In the next sections, we go into detail on each of these steps…

(For all the steps and more information on making Maple Syrup, be sure to check out the Maple Syrup Hub!)

How to Finish Boiling Maple Syrup – Step by Step Guide

This article assumes that you have already performed the bulk of the boiling of your maple sap to evaporate off most of the water content over a wood fire, a homemade contraption of some sort, or a propane turkey fryer.

Propane Boiler Boiling Maple Tree Sap to Make Maple Syrup
Boiling Maple Sap on a Propane Boiler

If you have a LOT of sap to boil down, I recommend a higher-capacity evaporator with a dual-burner setup.

The steps in this article go through how to finish boiling the sap to the correct consistency for perfectly flavored maple syrup!

1 – Pre-Filter the Syrup to Remove Larger Debris

To perform this step, we will want to poor the sap from your outdoor boiling vessel into a large 5-quart pot or similar, then put it on the stove.

But before doing this, filter the sap to remove any residue that has accumulated during the initial boiling phase. This will help to remove larger residue that remained in the sap from the initial boiling.

Sugar sand and Niter are natural precipitates that form in Maple Syrup as it is heated. They are not harmful to consume but are often filtered out in order to reduce cloudiness and increase the clarity of Maple Syrup.

Use a syrup filter and position it in a filter stand or strainer.

maple syrup sap filter prefilter mesh cheesecloth
A non-woven filter for maple syrup

Pour the sap through it. If the syrup filter gets too clogged and slows the filtering process, replace it with another one.

Filtering Maple Syrup Pre filter using a non-woven mesh filter
pre-filtering maple syrup

The filters are cheap and come in a pack of 50 or so. They are reusable and are easy to rinse out, so I like to have a couple handy to swap out if the filtering gets too slow.

Another common filter material used by many maple syrup makers is cheesecloth, which is the more traditional method of filtering sap.

Here is a photo showing the syrup filter after one round of filtering. You can see the sugar sand and particulates collected in the bottom of the filter.

Niter and sugar sand in the filter maple syrup
sugar-sand in the filter

This is a view of the maple syrup sugar sand caught in the filter.

maple syrup filter sugar sand niter
sugar sand

2 – Boiling the Maple Sap to 215°F

Once the sap is filtered, put it into the large pot and start up the stove and set it to a medium heat to get the sap boiling again. Insert your candy thermometer or digital thermometer so that the bulb is submerged in the sap, but not touching the bottom of the pot.

how to know when maple syrup is done refractometer
use a thermometer in the boiling pot

This spatula thermometer allows you to stir, take measurements and keep the thermometer from touching the bottom of the pot, all at the same time. In general, syrup does not require a lot of stirring, since the bubbles naturally ‘stir’ the pot!

Boiling Maple Sap to Make Maple Syrup
maple syrup boiling on a stove

Maple syrup boils at a higher temperature than water due to its sugar content. Water boils at 212°F, while maple syrup boils at 219°F.

For this reason, you want to continue boiling your sap until it reaches a temperature of 219°F.

Note: In general, you want to boil the sap until it reaches a temperature that is 7°F above the boiling temperature of water. So, if your area differs significantly from 212°F, add 7°F to the boiling point of water at your location.

3 – Filter the Syrup Once it has reached 215°F

A good practice to remove residue and reduce the amount of ‘sugar sand’ (or ‘niter’) that collects in your syrup, is to filter the syrup again at 215°F. Use another syrup filter as during the first filtering step.

Sugar sand develops during the boiling process as a precipitate, so it is not enough to filter just once, since the sugar sand is continually being created as the water evaporates off.

filtering maple syrup

4 – Boil the filtered sap to 219°F

After filtering at 215°F, put the syrup back on the stove and continue boiling until it reaches 219°F.

boiling maple syrup 219 degrees
Maple Syrup at 219 degrees

A couple of clues will occur as you approach the time when the maple syrup is done. You will notice that the consistency of the syrup seems to change as you approach the 219°F temperature.

Watch for these tell-tale signs:

  • The syrup will suddenly want to bubble over! The heat setting that you have been using on your stove all along, will suddenly be too hot.  Often this will happen the instant you put a spoon or stirring stick into the syrup. Turn the heat down little by little to keep the boiling going but to stop the syrup from boiling over.
  • The bubbles will change consistency and turn into larger, more viscous, more spherical, and stickier bubbles than before (not foam), like below.
maple syrup boiling near finished
Maple Syrup about to boil over

There may be a temptation to go to higher temperatures in order to achieve thicker syrup.

While this is the case, and the syrup will become thicker, it will also become more prone to crystallization.

Below is some maple syrup that was heated to 230°F. After several weeks on the shelf, significant ‘rock-candy’ crystallization had occurred.

crystalized maple syrup in a jar
crystalized maple syrup

How Do You Know When Maple Syrup is Done Boiling?

Once the sap has reached 219°F, let it boil at this level for another minute or so, then it is done. I find that knowing exactly when to stop boiling can seem a bit arbitrary!

It depends on how accurate your thermometer is, how quickly you get the syrup off the heat, and it’s easy to end up just ‘guessing’ when it is done. That is why I now use a refractometer.

According to the International Maple Syrup Institute, real maple syrup has between 66% and 68.9% sugar content. You want the syrup to be between 66-68.9% on the brix scale (66-68.9% sugar content) because lower than 66% and your syrup will be too watery.

And above 68.9%, your syrup will start to crystalize in the jars. So ideally, you measure the sugar content directly instead of only going by temperature.

The traditional method of measuring sugar content is to use a hydrometer. To use a hydrometer, you fill a test cup with syrup, then gently place the hydrometer into the syrup allowing it to float, then read off the number right at the surface level of the syrup.

Drawing of a hydrometer and test cup used to measure the density of Maple Syrup.
Hydrometer and Test Cup.

(A set of instructions on how to properly use a hydrometer can be found here.)

Hydrometers can be a bit confusing to use and lack precision unless you have built up experience using one. And since they are made of thin glass, they are quite fragile and prone to breaking.

After struggling to get good, consistent maple syrup, I finally stumbled onto the use of a refractometer. This device removes the ambiguity and allows you to be extremely precise by measuring the sugar content (brix %) directly. 

This is what I use now, and it is so much easier, since it only requires a few drops of syrup.

By the way, I wrote a whole post on How to Use a Refractometer for Maple Syrup.

For some reason I assumed a refractometer would cost hundreds of dollars, luckily, they don’t – far less, I was actually surprised at how inexpensive they are.

A refractometer costs less than a hydrometer, is less fragile, and is easier to use!

Ever since I bought one, it has made the whole maple syrup boiling process much simpler and removed the guesswork!

Using a refractometer has allowed me to achieve perfect syrup! If you’re on the fence, I highly recommend getting one, you won’t regret it.

Here is my refractometer in use.

Refractometer in case used for making and testing Maple Syrup
My refractometer for Maple Syrup

The maple syrup will boil for a long time at 212ºF, then it will start to climb. I watch the candy thermometer as a reference, and when it is indicating about 215ºF I start sampling with the refractometer.

boiling maple sap finishing using a refractometer
Testing Maple Syrup sugar content

I take a few drops from the pot and drip the syrup onto the viewing slide, then close the lid.

Using a refractometer to accurately determine the sugar content of maple syrup
Maple Syrup Refractometer
refractometer with maple syrup inside

After that, look into the viewport to read off the % sugar concentration (brix value). The line between blue and orange indicates the % sugar in your syrup.

This is not a ‘digital’ refractometer, it is analog (doesn’t require batteries). I read somewhere that a person thought it required sunlight – it doesn’t.

All I use is the normal overhead room light, and then look in the viewport (like a telescope), and it looks like the images I’ve pasted here.

In the image below, I was at about 66.4% which is about perfect. (If the scale is all blue – keep boiling, you are below the minimum reading.)

04-Maple-syrup-refractometer-66.5brix
Maple Syrup sugar content

In the picture below, I show 2 different batches. The one on the left is at the maximum (68.9%) and the one on the right is at the minimum (66%) brix values to technically be considered maple syrup.

maple-syrup-brix-range-refractometer
Refractometer readings for Maple Syrup

5 – Perform the Final Filtering

When the syrup is done boiling (around 219°F), you are now ready for the final filtering. This next step is very important, let the syrup cool slightly to around 180-190°F, then perform the final filtering.

This gives you time to get your synthetic filter and filter stand ready.

Note: If you filter at a higher temperature, sugar sand can still develop after the filtering! If that happens, your syrup will still look cloudy.

If you want to virtually eliminate all contaminants and sugar sand (niter) in your final product for a really nice, finished product, use a synthetic orlon filter for the final filtering.

The syrup in the picture below was filtered with a synthetic filter.

Have more questions? Check out my list of most Frequently Asked Questions about Maple Syrup Making!

Check out my PODCAST episode on How to Achieve Crystal Clear Maple Syrup!

filtered-maple-syrup
100% pure Delicious Maple Syrup

If you don’t care if there is some sugar sand in your syrup, go ahead and perform another mesh filter step and don’t worry about using a synthetic filter. Sugar sand is not harmful.

Sugar sand, or 'niter', is comprised of a potassium nitrate precipitate and is a normal byproduct of the maple syrup boiling process. It is perfectly safe to consume but can be a bit unsightly.

These pictures show maple syrup where only a mesh pre-filter has been used for filtering (3 times). Notice the sugar sand (niter) settled on the bottom of the jar.

It is perfectly safe to consume sugar sand. However, if you want that golden, honey-colored, transparent maple syrup, use a synthetic filter.

Synthetic filters are often made from a material called ‘Orlon’ which is a synthetic acrylic fiber first developed by DuPont. These have a filtering size of around 200 microns which effectively filters out the sugar sand.

Synthetic filters are normally used wet, meaning that they are soaked in hot water, then allowed to drip off before being used for filtering. If a synthetic filter is used dry, the filtering will not be as efficient, and will take much longer.

The use of a synthetic filter will remove almost all traces of sugar sand, leaving you with crystal clear, golden syrup!

Rinse the synthetic filter with hot water (don’t use soap) immediately after you are done, then let it drip-dry (don’t wring it out) and it will last for years. For larger batches, use a 3 qt synthetic filter.

The following image shows syrup from the same batch that has been filtered with only a mesh pre-filter (left), and maple syrup that has been filtered with both a mesh filter and a synthetic filter (right).

Notice the lack of sugar sand at the bottom of the jar, as well as the overall increased clarity of the syrup itself for the synthetic-filtered syrup.

filtered-maple-syrup-compare
Non-filtered (left) and Filtered Maple Syrup (right)

The final filtering process is done by putting one or more mesh pre-filters inside of the synthetic filter.

The pre-filter helps to catch any larger pieces of debris before the syrup goes through the synthetic filter, so that you don’t clog up the fine mesh of the synthetic filter.

Maple-Syrup-Final-Filtering-pre-filter-synthetic-filter

Once the syrup has reached 180-190°F, carefully pour it through the two filters. If the syrup filter starts to clog, replace it with another one.

Nesting several filters together inside the synthetic filter is a convenient approach, since you can remove the inner one as it begins to clog up.

Here is a picture showing the final filtering process with a regular filter nested inside of the synthetic filter.

Synthetic-Orlon-Maple-Syrup-Final-Filtering-PracticalMechanic

The syrup will pass through the synthetic filter relatively slowly. It helps to have the synthetic filter wet with hot water and allowed to drip dry before using it.

6 – As a Final Step, Can or Bottle the Finished syrup while it is still hot

Use a food-grade funnel to pour the syrup into clean canning jars or Maple Syrup Bottles (with ‘finger-hook’ handles) while it is still hot.

canning maple syrup using a funnel

When you hear a ‘pop’, you know that they have sealed. Make sure your lids seal properly, if they don’t, your syrup can spoil! Some recommend using new lids every time you can, for this very reason.

To put the finishing touches on your Maple Syrup Jars, print out some Free 2″ Maple Syrup Labels!

Canning maple syrup ball canning jars

If you started out with 5 gallons of sap, you would end up with somewhere around 20 oz of pure maple syrup (32:1).

Of course, this depends on a number of factors related to the sugar content of the sap produced by your trees but can be used as a rule of thumb.

The final product is incredibly beautiful; it looks like a jewel.
filtered maple syrup in the sun

Grades of Maple Syrup

As you may know, the color of the syrup that you produce will change over the course of the maple sugaring season, so don’t be surprised if your batches look different from one another!

Lighter syrup comes from the first sap that is harvested, and the color darkens as the season progresses. There is a maple syrup grading system established by the USDA to classify the grades of maple syrup.

Other factors that contribute to the color of your maple syrup include the type of maple trees you are tapping your maple sap from, and how long you boil it for.

In general, smaller batches that are boiled from start to finish without adding more sap as you go along, will be lighter in color.

Larger batches where sap is continually added to the evaporator (boiling vessel) will be darker in color due to the increased time allowed for the Maillard Reaction to take place.

I have had cases where I had to stop boiling mid-way through, so I put the syrup in the refrigerator overnight and continued boiling in the morning. That produced a very dark (and tasty) syrup!

grades of maple syrup

Syrup can sit on the shelf indefinitely but should be refrigerated after opening the sealed jars.

I love fresh maple syrup so much, but it sure is sticky, so consider using a dripless syrup dispenser – clean and easy with no stickiness!

Congratulations! Enjoy your self-made maple syrup!

maple syrup with pancakes!

I hope you found this helpful! I know that harvesting maple sap and boiling it into fresh maple syrup is a highlight of the spring for my family! I hope it is for you and yours as well!

I love getting comments and especially hearing stories about how other people boil and make maple syrup! Please leave a comment on any tips and tricks that have worked well for you!

Supplies mentioned in this Article:

Note: Click here to download a 1-page PDF "Maple Syrup Making Cheat Sheet" that contains a summarized version of all the steps to making delicious Maple Syrup!

Additional Articles in this Series on Maple Syrup Making!

For all the steps and more information on making Maple Syrup, be sure to check out the Maple Syrup Hub!

These are the links to the other articles in this series:

Play the “How to Make Maple Syrup Podcast!”

Identifying Maple Trees, Sugar Content, and Taste (Rebroadcast) How to Make Maple Syrup!

In this episode, we'll discuss: 1. How to identify maple trees and some specifics of the different varieties. 2. The sugar content of different Maple Trees. 3. How sugar content varies over the season and from year to year. 3. We'll then talk to Rachel and get her take on the taste of Maple Syrup from different Maple Trees. Download the FREE – How to Make Maple Syrup Cheat Sheet found here: https://practicalmechanic.com/maplesyrup Welcome to the "How to Make Maple Syrup Podcast"! My name is Richard Tomlinsen, and in this series, I am going to walk through, in detail, the super easy steps to follow to make your own delicious Maple Syrup! My Goal is that by the end of listening to this series, you will have all of the information you need to get started tapping your maple trees, collecting the sap, boiling it, and finally performing the finishing boil in order to bottle that perfect golden elixir! In this 5-part series we are going to cover the following topics: 1. How to Identify and When to Collect Sap (What kinds of Maples can produce Syrup? How many do you need?) 2. How to Tap Maple Trees for Maple Syrup (Including best practices for keeping your trees healthy!) 3. How to Boil Sap for Maple Syrup (Easiest methods and how long it will take!) 4. How to Perfect the Finishing Boil (Take the guesswork out of "When is my syrup done?") 5. How to Bottle Maple Syrup (Tips for bottling Maple Syrup for your Family and Friends!) I hope you have as much fun listening as we are having making these episodes! Why am I doing this? I love making maple syrup! It has been a tradition in my family ever since I was very young, and it brings so much joy to our family! I hope to bring that joy to you as well! I hope that after you have listened to this podcast series, you will be equipped with how to start a fun, inexpensive hobby that you can do with your family and friends to draw closer to each other! — Send in a voice message: https://anchor.fm/how-to-make-maple-syrup/message
  1. Identifying Maple Trees, Sugar Content, and Taste (Rebroadcast)
  2. Introducing the "How to Make Maple Syrup" Podcast! (Rebroadcast)
  3. Top 5 Lesser-Known Mistakes When Making Maple Syrup
  4. What are the Top 5 Most Common Mistakes When Making Maple Syrup?

The “How to Make Maple Syrup Podcast!” is enjoyed by hundreds of listeners each week during the maple-sugaring season. We’d love for you to join us! We discuss our favorite tips and tricks for making maple syrup as well as interesting information related to the golden elixir!

Click on the buttons below to listen on your favorite podcast player!

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How to Make Maple Syrup Podcast!

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How to Make Maple Syrup on YouTube - Practical Mechanic
Watch “How to Make Maple Syrup in 4 Minutes” on YouTube!

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